Re: \if, \elseif, \else, \endif (was Re: PSQL commands: \quit_if, \quit_unless) - Mailing list pgsql-hackers

From Tom Lane
Subject Re: \if, \elseif, \else, \endif (was Re: PSQL commands: \quit_if, \quit_unless)
Date
Msg-id 10990.1490847359@sss.pgh.pa.us
Whole thread Raw
In response to Re: \if, \elseif, \else, \endif (was Re: PSQL commands:\quit_if, \quit_unless)  (Fabien COELHO <coelho@cri.ensmp.fr>)
Responses Re: \if, \elseif, \else, \endif (was Re: PSQL commands:\quit_if, \quit_unless)  ("Daniel Verite" <daniel@manitou-mail.org>)
Re: \if, \elseif, \else, \endif (was Re: PSQL commands:\quit_if, \quit_unless)  (Fabien COELHO <coelho@cri.ensmp.fr>)
List pgsql-hackers
Fabien COELHO <coelho@cri.ensmp.fr> writes:
>> New Patch v29: Now with less coverage!

> Patch applies cleanly. Make check ok. Feature still works!

I've been hacking on this for about two full days now, and have gotten
it to a point where I think it's committable.  Aside from cosmetic
changes, I've made it behave reasonably for cases where \if is used
on portions of a query, for instance

SELECT
\if :something
    var1
\else
    var2
\endif
FROM table;

which as I mentioned a long time ago is something that people will
certainly expect to work.  I also cleaned up a lot of corner-case
discrepancies between how much text is consumed in active-branch and
inactive-branch cases (OT_FILEPIPE is a particularly nasty case in that
regard :-()

I plan to read this over again tomorrow and then push it, if there are
not objections/corrections.

            regards, tom lane

diff --git a/doc/src/sgml/ref/psql-ref.sgml b/doc/src/sgml/ref/psql-ref.sgml
index 2a9c412..b51b11b 100644
*** a/doc/src/sgml/ref/psql-ref.sgml
--- b/doc/src/sgml/ref/psql-ref.sgml
*************** hello 10
*** 2064,2069 ****
--- 2064,2158 ----


        <varlistentry>
+         <term><literal>\if</literal> <replaceable class="parameter">expression</replaceable></term>
+         <term><literal>\elif</literal> <replaceable class="parameter">expression</replaceable></term>
+         <term><literal>\else</literal></term>
+         <term><literal>\endif</literal></term>
+         <listitem>
+         <para>
+         This group of commands implements nestable conditional blocks.
+         A conditional block must begin with an <command>\if</command> and end
+         with an <command>\endif</command>.  In between there may be any number
+         of <command>\elif</command> clauses, which may optionally be followed
+         by a single <command>\else</command> clause.  Ordinary queries and
+         other types of backslash commands may (and usually do) appear between
+         the commands forming a conditional block.
+         </para>
+         <para>
+         The <command>\if</command> and <command>\elif</command> commands read
+         their argument(s) and evaluate them as a boolean expression.  If the
+         expression yields <literal>true</literal> then processing continues
+         normally; otherwise, lines are skipped until a
+         matching <command>\elif</command>, <command>\else</command>,
+         or <command>\endif</command> is reached.  Once
+         an <command>\if</command> or <command>\elif</command> test has
+         succeeded, the arguments of later <command>\elif</command> commands in
+         the same block are not evaluated but are treated as false.  Lines
+         following an <command>\else</command> are processed only if no earlier
+         matching <command>\if</command> or <command>\elif</command> succeeded.
+         </para>
+         <para>
+         The <replaceable class="parameter">expression</replaceable> argument
+         of an <command>\if</command> or <command>\elif</command> command
+         is subject to variable interpolation and backquote expansion, just
+         like any other backslash command argument.  After that it is evaluated
+         like the value of an on/off option variable.  So a valid value
+         is any unambiguous case-insensitive match for one of:
+         <literal>true</literal>, <literal>false</literal>, <literal>1</literal>,
+         <literal>0</literal>, <literal>on</literal>, <literal>off</literal>,
+         <literal>yes</literal>, <literal>no</literal>.  For example,
+         <literal>t</literal>, <literal>T</literal>, and <literal>tR</literal>
+         will all be considered to be <literal>true</literal>.
+         </para>
+         <para>
+         Expressions that do not properly evaluate to true or false will
+         generate a warning and be treated as false.
+         </para>
+         <para>
+         Lines being skipped are parsed normally to identify queries and
+         backslash commands, but queries are not sent to the server, and
+         backslash commands other than conditionals
+         (<command>\if</command>, <command>\elif</command>,
+         <command>\else</command>, <command>\endif</command>) are
+         ignored.  Conditional commands are checked only for valid nesting.
+         Variable references in skipped lines are not expanded, and backquote
+         expansion is not performed either.
+         </para>
+         <para>
+         All the backslash commands of a given conditional block must appear in
+         the same source file. If EOF is reached on the main input file or an
+         <command>\include</command>-ed file before all local
+         <command>\if</command>-blocks have been closed,
+         then <application>psql</> will raise an error.
+         </para>
+         <para>
+          Here is an example:
+         </para>
+ <programlisting>
+ -- check for the existence of two separate records in the database and store
+ -- the results in separate psql variables
+ SELECT
+     EXISTS(SELECT 1 FROM customer WHERE customer_id = 123) as is_customer,
+     EXISTS(SELECT 1 FROM employee WHERE employee_id = 456) as is_employee
+ \gset
+ \if :is_customer
+     SELECT * FROM customer WHERE customer_id = 123;
+ \elif :is_employee
+     \echo 'is not a customer but is an employee'
+     SELECT * FROM employee WHERE employee_id = 456;
+ \else
+     \if yes
+         \echo 'not a customer or employee'
+     \else
+         \echo 'this will never print'
+     \endif
+ \endif
+ </programlisting>
+         </listitem>
+       </varlistentry>
+
+
+       <varlistentry>
          <term><literal>\l[+]</literal> or <literal>\list[+] [ <link linkend="APP-PSQL-patterns"><replaceable
class="parameter">pattern</replaceable></link>]</literal></term> 
          <listitem>
          <para>
*************** testdb=> <userinput>INSERT INTO my_ta
*** 3715,3721 ****
          <listitem>
          <para>
          In prompt 1 normally <literal>=</literal>,
!         but <literal>^</literal> if in single-line mode,
          or <literal>!</literal> if the session is disconnected from the
          database (which can happen if <command>\connect</command> fails).
          In prompt 2 <literal>%R</literal> is replaced by a character that
--- 3804,3811 ----
          <listitem>
          <para>
          In prompt 1 normally <literal>=</literal>,
!         but <literal>@</literal> if the session is in an inactive branch of a
!         conditional block, or <literal>^</literal> if in single-line mode,
          or <literal>!</literal> if the session is disconnected from the
          database (which can happen if <command>\connect</command> fails).
          In prompt 2 <literal>%R</literal> is replaced by a character that
diff --git a/src/bin/psql/Makefile b/src/bin/psql/Makefile
index f8e31ea..ab2cfa6 100644
*** a/src/bin/psql/Makefile
--- b/src/bin/psql/Makefile
*************** REFDOCDIR= $(top_srcdir)/doc/src/sgml/re
*** 21,30 ****
  override CPPFLAGS := -I. -I$(srcdir) -I$(libpq_srcdir) $(CPPFLAGS)
  LDFLAGS += -L$(top_builddir)/src/fe_utils -lpgfeutils -lpq

! OBJS=    command.o common.o help.o input.o stringutils.o mainloop.o copy.o \
!     startup.o prompt.o variables.o large_obj.o describe.o \
!     crosstabview.o tab-complete.o \
!     sql_help.o psqlscanslash.o \
      $(WIN32RES)


--- 21,30 ----
  override CPPFLAGS := -I. -I$(srcdir) -I$(libpq_srcdir) $(CPPFLAGS)
  LDFLAGS += -L$(top_builddir)/src/fe_utils -lpgfeutils -lpq

! OBJS=    command.o common.o conditional.o copy.o crosstabview.o \
!     describe.o help.o input.o large_obj.o mainloop.o \
!     prompt.o psqlscanslash.o sql_help.o startup.o stringutils.o \
!     tab-complete.o variables.o \
      $(WIN32RES)


diff --git a/src/bin/psql/command.c b/src/bin/psql/command.c
index 4f4a0aa..e278511 100644
*** a/src/bin/psql/command.c
--- b/src/bin/psql/command.c
*************** typedef enum EditableObjectType
*** 56,69 ****
      EditableView
  } EditableObjectType;

! /* functions for use in this file */
  static backslashResult exec_command(const char *cmd,
               PsqlScanState scan_state,
!              PQExpBuffer query_buf);
! static bool do_edit(const char *filename_arg, PQExpBuffer query_buf,
!         int lineno, bool *edited);
  static bool do_connect(enum trivalue reuse_previous_specification,
             char *dbname, char *user, char *host, char *port);
  static bool do_shell(const char *command);
  static bool do_watch(PQExpBuffer query_buf, double sleep);
  static bool lookup_object_oid(EditableObjectType obj_type, const char *desc,
--- 56,158 ----
      EditableView
  } EditableObjectType;

! /* local function declarations */
  static backslashResult exec_command(const char *cmd,
               PsqlScanState scan_state,
!              ConditionalStack cstack,
!              PQExpBuffer query_buf,
!              PQExpBuffer previous_buf);
! static backslashResult exec_command_a(PsqlScanState scan_state, bool active_branch);
! static backslashResult exec_command_C(PsqlScanState scan_state, bool active_branch);
! static backslashResult exec_command_connect(PsqlScanState scan_state, bool active_branch);
! static backslashResult exec_command_cd(PsqlScanState scan_state, bool active_branch,
!                 const char *cmd);
! static backslashResult exec_command_conninfo(PsqlScanState scan_state, bool active_branch);
! static backslashResult exec_command_copy(PsqlScanState scan_state, bool active_branch);
! static backslashResult exec_command_copyright(PsqlScanState scan_state, bool active_branch);
! static backslashResult exec_command_crosstabview(PsqlScanState scan_state, bool active_branch);
! static backslashResult exec_command_d(PsqlScanState scan_state, bool active_branch,
!                const char *cmd);
! static backslashResult exec_command_edit(PsqlScanState scan_state, bool active_branch,
!                   PQExpBuffer query_buf, PQExpBuffer previous_buf);
! static backslashResult exec_command_ef(PsqlScanState scan_state, bool active_branch,
!                 PQExpBuffer query_buf);
! static backslashResult exec_command_ev(PsqlScanState scan_state, bool active_branch,
!                 PQExpBuffer query_buf);
! static backslashResult exec_command_echo(PsqlScanState scan_state, bool active_branch,
!                   const char *cmd);
! static backslashResult exec_command_elif(PsqlScanState scan_state, ConditionalStack cstack,
!                   PQExpBuffer query_buf);
! static backslashResult exec_command_else(PsqlScanState scan_state, ConditionalStack cstack,
!                   PQExpBuffer query_buf);
! static backslashResult exec_command_endif(PsqlScanState scan_state, ConditionalStack cstack,
!                    PQExpBuffer query_buf);
! static backslashResult exec_command_encoding(PsqlScanState scan_state, bool active_branch);
! static backslashResult exec_command_errverbose(PsqlScanState scan_state, bool active_branch);
! static backslashResult exec_command_f(PsqlScanState scan_state, bool active_branch);
! static backslashResult exec_command_g(PsqlScanState scan_state, bool active_branch,
!                const char *cmd);
! static backslashResult exec_command_gexec(PsqlScanState scan_state, bool active_branch);
! static backslashResult exec_command_gset(PsqlScanState scan_state, bool active_branch);
! static backslashResult exec_command_help(PsqlScanState scan_state, bool active_branch);
! static backslashResult exec_command_html(PsqlScanState scan_state, bool active_branch);
! static backslashResult exec_command_include(PsqlScanState scan_state, bool active_branch,
!                      const char *cmd);
! static backslashResult exec_command_if(PsqlScanState scan_state, ConditionalStack cstack,
!                 PQExpBuffer query_buf);
! static backslashResult exec_command_list(PsqlScanState scan_state, bool active_branch,
!                   const char *cmd);
! static backslashResult exec_command_lo(PsqlScanState scan_state, bool active_branch,
!                 const char *cmd);
! static backslashResult exec_command_out(PsqlScanState scan_state, bool active_branch);
! static backslashResult exec_command_print(PsqlScanState scan_state, bool active_branch,
!                    PQExpBuffer query_buf);
! static backslashResult exec_command_password(PsqlScanState scan_state, bool active_branch);
! static backslashResult exec_command_prompt(PsqlScanState scan_state, bool active_branch,
!                     const char *cmd);
! static backslashResult exec_command_pset(PsqlScanState scan_state, bool active_branch);
! static backslashResult exec_command_quit(PsqlScanState scan_state, bool active_branch);
! static backslashResult exec_command_reset(PsqlScanState scan_state, bool active_branch,
!                    PQExpBuffer query_buf);
! static backslashResult exec_command_s(PsqlScanState scan_state, bool active_branch);
! static backslashResult exec_command_set(PsqlScanState scan_state, bool active_branch);
! static backslashResult exec_command_setenv(PsqlScanState scan_state, bool active_branch,
!                     const char *cmd);
! static backslashResult exec_command_sf(PsqlScanState scan_state, bool active_branch,
!                 const char *cmd);
! static backslashResult exec_command_sv(PsqlScanState scan_state, bool active_branch,
!                 const char *cmd);
! static backslashResult exec_command_t(PsqlScanState scan_state, bool active_branch);
! static backslashResult exec_command_T(PsqlScanState scan_state, bool active_branch);
! static backslashResult exec_command_timing(PsqlScanState scan_state, bool active_branch);
! static backslashResult exec_command_unset(PsqlScanState scan_state, bool active_branch,
!                    const char *cmd);
! static backslashResult exec_command_write(PsqlScanState scan_state, bool active_branch,
!                    const char *cmd,
!                    PQExpBuffer query_buf, PQExpBuffer previous_buf);
! static backslashResult exec_command_watch(PsqlScanState scan_state, bool active_branch,
!                    PQExpBuffer query_buf, PQExpBuffer previous_buf);
! static backslashResult exec_command_x(PsqlScanState scan_state, bool active_branch);
! static backslashResult exec_command_z(PsqlScanState scan_state, bool active_branch);
! static backslashResult exec_command_shell_escape(PsqlScanState scan_state, bool active_branch);
! static backslashResult exec_command_slash_command_help(PsqlScanState scan_state, bool active_branch);
! static char *read_connect_arg(PsqlScanState scan_state);
! static PQExpBuffer gather_boolean_expression(PsqlScanState scan_state);
! static bool is_true_boolean_expression(PsqlScanState scan_state, const char *name);
! static void ignore_boolean_expression(PsqlScanState scan_state);
! static void ignore_slash_options(PsqlScanState scan_state);
! static void ignore_slash_filepipe(PsqlScanState scan_state);
! static void ignore_slash_whole_line(PsqlScanState scan_state);
! static bool is_branching_command(const char *cmd);
! static void save_query_text_state(PsqlScanState scan_state, ConditionalStack cstack,
!                       PQExpBuffer query_buf);
! static void discard_query_text(PsqlScanState scan_state, ConditionalStack cstack,
!                    PQExpBuffer query_buf);
! static void copy_previous_query(PQExpBuffer query_buf, PQExpBuffer previous_buf);
  static bool do_connect(enum trivalue reuse_previous_specification,
             char *dbname, char *user, char *host, char *port);
+ static bool do_edit(const char *filename_arg, PQExpBuffer query_buf,
+         int lineno, bool *edited);
  static bool do_shell(const char *command);
  static bool do_watch(PQExpBuffer query_buf, double sleep);
  static bool lookup_object_oid(EditableObjectType obj_type, const char *desc,
*************** static void checkWin32Codepage(void);
*** 96,104 ****
   * just after the '\'.  The lexer is advanced past the command and all
   * arguments on return.
   *
!  * 'query_buf' contains the query-so-far, which may be modified by
   * execution of the backslash command (for example, \r clears it).
!  * query_buf can be NULL if there is no query so far.
   *
   * Returns a status code indicating what action is desired, see command.h.
   *----------
--- 185,202 ----
   * just after the '\'.  The lexer is advanced past the command and all
   * arguments on return.
   *
!  * cstack is the current \if stack state.  This will be examined, and
!  * possibly modified by conditional commands.
!  *
!  * query_buf contains the query-so-far, which may be modified by
   * execution of the backslash command (for example, \r clears it).
!  *
!  * previous_buf contains the query most recently sent to the server
!  * (empty if none yet).  This should not be modified here, but some
!  * commands copy its content into query_buf.
!  *
!  * query_buf and previous_buf will be NULL when executing a "-c"
!  * command-line option.
   *
   * Returns a status code indicating what action is desired, see command.h.
   *----------
*************** static void checkWin32Codepage(void);
*** 106,124 ****

  backslashResult
  HandleSlashCmds(PsqlScanState scan_state,
!                 PQExpBuffer query_buf)
  {
!     backslashResult status = PSQL_CMD_SKIP_LINE;
      char       *cmd;
      char       *arg;

      Assert(scan_state != NULL);

      /* Parse off the command name */
      cmd = psql_scan_slash_command(scan_state);

      /* And try to execute it */
!     status = exec_command(cmd, scan_state, query_buf);

      if (status == PSQL_CMD_UNKNOWN)
      {
--- 204,225 ----

  backslashResult
  HandleSlashCmds(PsqlScanState scan_state,
!                 ConditionalStack cstack,
!                 PQExpBuffer query_buf,
!                 PQExpBuffer previous_buf)
  {
!     backslashResult status;
      char       *cmd;
      char       *arg;

      Assert(scan_state != NULL);
+     Assert(cstack != NULL);

      /* Parse off the command name */
      cmd = psql_scan_slash_command(scan_state);

      /* And try to execute it */
!     status = exec_command(cmd, scan_state, cstack, query_buf, previous_buf);

      if (status == PSQL_CMD_UNKNOWN)
      {
*************** HandleSlashCmds(PsqlScanState scan_state
*** 131,144 ****

      if (status != PSQL_CMD_ERROR)
      {
!         /* eat any remaining arguments after a valid command */
!         /* note we suppress evaluation of backticks here */
          while ((arg = psql_scan_slash_option(scan_state,
!                                              OT_NO_EVAL, NULL, false)))
          {
!             psql_error("\\%s: extra argument \"%s\" ignored\n", cmd, arg);
              free(arg);
          }
      }
      else
      {
--- 232,253 ----

      if (status != PSQL_CMD_ERROR)
      {
!         /*
!          * Eat any remaining arguments after a valid command.  We want to
!          * suppress evaluation of backticks in this situation, so transiently
!          * push an inactive conditional-stack entry.
!          */
!         bool        active_branch = conditional_active(cstack);
!
!         conditional_stack_push(cstack, IFSTATE_IGNORED);
          while ((arg = psql_scan_slash_option(scan_state,
!                                              OT_NORMAL, NULL, false)))
          {
!             if (active_branch)
!                 psql_error("\\%s: extra argument \"%s\" ignored\n", cmd, arg);
              free(arg);
          }
+         conditional_stack_pop(cstack);
      }
      else
      {
*************** HandleSlashCmds(PsqlScanState scan_state
*** 159,214 ****
      return status;
  }

  /*
!  * Read and interpret an argument to the \connect slash command.
   */
! static char *
! read_connect_arg(PsqlScanState scan_state)
  {
!     char       *result;
!     char        quote;

      /*
!      * Ideally we should treat the arguments as SQL identifiers.  But for
!      * backwards compatibility with 7.2 and older pg_dump files, we have to
!      * take unquoted arguments verbatim (don't downcase them). For now,
!      * double-quoted arguments may be stripped of double quotes (as if SQL
!      * identifiers).  By 7.4 or so, pg_dump files can be expected to
!      * double-quote all mixed-case \connect arguments, and then we can get rid
!      * of OT_SQLIDHACK.
       */
!     result = psql_scan_slash_option(scan_state, OT_SQLIDHACK, "e, true);
!
!     if (!result)
!         return NULL;

!     if (quote)
!         return result;

!     if (*result == '\0' || strcmp(result, "-") == 0)
!         return NULL;

!     return result;
  }


  /*
!  * Subroutine to actually try to execute a backslash command.
   */
  static backslashResult
! exec_command(const char *cmd,
!              PsqlScanState scan_state,
!              PQExpBuffer query_buf)
  {
!     bool        success = true; /* indicate here if the command ran ok or
!                                  * failed */
!     backslashResult status = PSQL_CMD_SKIP_LINE;

!     /*
!      * \a -- toggle field alignment This makes little sense but we keep it
!      * around.
!      */
!     if (strcmp(cmd, "a") == 0)
      {
          if (pset.popt.topt.format != PRINT_ALIGNED)
              success = do_pset("format", "aligned", &pset.popt, pset.quiet);
--- 268,436 ----
      return status;
  }

+
  /*
!  * Subroutine to actually try to execute a backslash command.
!  *
!  * The typical "success" result code is PSQL_CMD_SKIP_LINE, although some
!  * commands return something else.  Failure results are PSQL_CMD_ERROR,
!  * unless PSQL_CMD_UNKNOWN is more appropriate.
   */
! static backslashResult
! exec_command(const char *cmd,
!              PsqlScanState scan_state,
!              ConditionalStack cstack,
!              PQExpBuffer query_buf,
!              PQExpBuffer previous_buf)
  {
!     backslashResult status;
!     bool        active_branch = conditional_active(cstack);

      /*
!      * In interactive mode, warn when we're ignoring a command within a false
!      * \if-branch.  But we continue on, so as to parse and discard the right
!      * number of parameters.  Each individual backslash command subroutine is
!      * responsible for doing nothing after discarding appropriate arguments,
!      * if !active_branch.
       */
!     if (pset.cur_cmd_interactive && !active_branch &&
!         !is_branching_command(cmd))
!     {
!         psql_error("\\%s command ignored; use \\endif or Ctrl-C to exit current \\if block\n",
!                    cmd);
!     }

!     if (strcmp(cmd, "a") == 0)
!         status = exec_command_a(scan_state, active_branch);
!     else if (strcmp(cmd, "C") == 0)
!         status = exec_command_C(scan_state, active_branch);
!     else if (strcmp(cmd, "c") == 0 || strcmp(cmd, "connect") == 0)
!         status = exec_command_connect(scan_state, active_branch);
!     else if (strcmp(cmd, "cd") == 0)
!         status = exec_command_cd(scan_state, active_branch, cmd);
!     else if (strcmp(cmd, "conninfo") == 0)
!         status = exec_command_conninfo(scan_state, active_branch);
!     else if (pg_strcasecmp(cmd, "copy") == 0)
!         status = exec_command_copy(scan_state, active_branch);
!     else if (strcmp(cmd, "copyright") == 0)
!         status = exec_command_copyright(scan_state, active_branch);
!     else if (strcmp(cmd, "crosstabview") == 0)
!         status = exec_command_crosstabview(scan_state, active_branch);
!     else if (cmd[0] == 'd')
!         status = exec_command_d(scan_state, active_branch, cmd);
!     else if (strcmp(cmd, "e") == 0 || strcmp(cmd, "edit") == 0)
!         status = exec_command_edit(scan_state, active_branch,
!                                    query_buf, previous_buf);
!     else if (strcmp(cmd, "ef") == 0)
!         status = exec_command_ef(scan_state, active_branch, query_buf);
!     else if (strcmp(cmd, "ev") == 0)
!         status = exec_command_ev(scan_state, active_branch, query_buf);
!     else if (strcmp(cmd, "echo") == 0 || strcmp(cmd, "qecho") == 0)
!         status = exec_command_echo(scan_state, active_branch, cmd);
!     else if (strcmp(cmd, "elif") == 0)
!         status = exec_command_elif(scan_state, cstack, query_buf);
!     else if (strcmp(cmd, "else") == 0)
!         status = exec_command_else(scan_state, cstack, query_buf);
!     else if (strcmp(cmd, "endif") == 0)
!         status = exec_command_endif(scan_state, cstack, query_buf);
!     else if (strcmp(cmd, "encoding") == 0)
!         status = exec_command_encoding(scan_state, active_branch);
!     else if (strcmp(cmd, "errverbose") == 0)
!         status = exec_command_errverbose(scan_state, active_branch);
!     else if (strcmp(cmd, "f") == 0)
!         status = exec_command_f(scan_state, active_branch);
!     else if (strcmp(cmd, "g") == 0 || strcmp(cmd, "gx") == 0)
!         status = exec_command_g(scan_state, active_branch, cmd);
!     else if (strcmp(cmd, "gexec") == 0)
!         status = exec_command_gexec(scan_state, active_branch);
!     else if (strcmp(cmd, "gset") == 0)
!         status = exec_command_gset(scan_state, active_branch);
!     else if (strcmp(cmd, "h") == 0 || strcmp(cmd, "help") == 0)
!         status = exec_command_help(scan_state, active_branch);
!     else if (strcmp(cmd, "H") == 0 || strcmp(cmd, "html") == 0)
!         status = exec_command_html(scan_state, active_branch);
!     else if (strcmp(cmd, "i") == 0 || strcmp(cmd, "include") == 0 ||
!              strcmp(cmd, "ir") == 0 || strcmp(cmd, "include_relative") == 0)
!         status = exec_command_include(scan_state, active_branch, cmd);
!     else if (strcmp(cmd, "if") == 0)
!         status = exec_command_if(scan_state, cstack, query_buf);
!     else if (strcmp(cmd, "l") == 0 || strcmp(cmd, "list") == 0 ||
!              strcmp(cmd, "l+") == 0 || strcmp(cmd, "list+") == 0)
!         status = exec_command_list(scan_state, active_branch, cmd);
!     else if (strncmp(cmd, "lo_", 3) == 0)
!         status = exec_command_lo(scan_state, active_branch, cmd);
!     else if (strcmp(cmd, "o") == 0 || strcmp(cmd, "out") == 0)
!         status = exec_command_out(scan_state, active_branch);
!     else if (strcmp(cmd, "p") == 0 || strcmp(cmd, "print") == 0)
!         status = exec_command_print(scan_state, active_branch, query_buf);
!     else if (strcmp(cmd, "password") == 0)
!         status = exec_command_password(scan_state, active_branch);
!     else if (strcmp(cmd, "prompt") == 0)
!         status = exec_command_prompt(scan_state, active_branch, cmd);
!     else if (strcmp(cmd, "pset") == 0)
!         status = exec_command_pset(scan_state, active_branch);
!     else if (strcmp(cmd, "q") == 0 || strcmp(cmd, "quit") == 0)
!         status = exec_command_quit(scan_state, active_branch);
!     else if (strcmp(cmd, "r") == 0 || strcmp(cmd, "reset") == 0)
!         status = exec_command_reset(scan_state, active_branch, query_buf);
!     else if (strcmp(cmd, "s") == 0)
!         status = exec_command_s(scan_state, active_branch);
!     else if (strcmp(cmd, "set") == 0)
!         status = exec_command_set(scan_state, active_branch);
!     else if (strcmp(cmd, "setenv") == 0)
!         status = exec_command_setenv(scan_state, active_branch, cmd);
!     else if (strcmp(cmd, "sf") == 0 || strcmp(cmd, "sf+") == 0)
!         status = exec_command_sf(scan_state, active_branch, cmd);
!     else if (strcmp(cmd, "sv") == 0 || strcmp(cmd, "sv+") == 0)
!         status = exec_command_sv(scan_state, active_branch, cmd);
!     else if (strcmp(cmd, "t") == 0)
!         status = exec_command_t(scan_state, active_branch);
!     else if (strcmp(cmd, "T") == 0)
!         status = exec_command_T(scan_state, active_branch);
!     else if (strcmp(cmd, "timing") == 0)
!         status = exec_command_timing(scan_state, active_branch);
!     else if (strcmp(cmd, "unset") == 0)
!         status = exec_command_unset(scan_state, active_branch, cmd);
!     else if (strcmp(cmd, "w") == 0 || strcmp(cmd, "write") == 0)
!         status = exec_command_write(scan_state, active_branch, cmd,
!                                     query_buf, previous_buf);
!     else if (strcmp(cmd, "watch") == 0)
!         status = exec_command_watch(scan_state, active_branch,
!                                     query_buf, previous_buf);
!     else if (strcmp(cmd, "x") == 0)
!         status = exec_command_x(scan_state, active_branch);
!     else if (strcmp(cmd, "z") == 0)
!         status = exec_command_z(scan_state, active_branch);
!     else if (strcmp(cmd, "!") == 0)
!         status = exec_command_shell_escape(scan_state, active_branch);
!     else if (strcmp(cmd, "?") == 0)
!         status = exec_command_slash_command_help(scan_state, active_branch);
!     else
!         status = PSQL_CMD_UNKNOWN;

!     /*
!      * All the commands that return PSQL_CMD_SEND want to execute previous_buf
!      * if query_buf is empty.  For convenience we implement that here, not in
!      * the individual command subroutines.
!      */
!     if (status == PSQL_CMD_SEND)
!         copy_previous_query(query_buf, previous_buf);

!     return status;
  }


  /*
!  * \a -- toggle field alignment
!  *
!  * This makes little sense but we keep it around.
   */
  static backslashResult
! exec_command_a(PsqlScanState scan_state, bool active_branch)
  {
!     bool        success = true;

!     if (active_branch)
      {
          if (pset.popt.topt.format != PRINT_ALIGNED)
              success = do_pset("format", "aligned", &pset.popt, pset.quiet);
*************** exec_command(const char *cmd,
*** 216,223 ****
              success = do_pset("format", "unaligned", &pset.popt, pset.quiet);
      }

!     /* \C -- override table title (formerly change HTML caption) */
!     else if (strcmp(cmd, "C") == 0)
      {
          char       *opt = psql_scan_slash_option(scan_state,
                                                   OT_NORMAL, NULL, true);
--- 438,455 ----
              success = do_pset("format", "unaligned", &pset.popt, pset.quiet);
      }

!     return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
! }
!
! /*
!  * \C -- override table title (formerly change HTML caption)
!  */
! static backslashResult
! exec_command_C(PsqlScanState scan_state, bool active_branch)
! {
!     bool        success = true;
!
!     if (active_branch)
      {
          char       *opt = psql_scan_slash_option(scan_state,
                                                   OT_NORMAL, NULL, true);
*************** exec_command(const char *cmd,
*** 225,244 ****
          success = do_pset("title", opt, &pset.popt, pset.quiet);
          free(opt);
      }

!     /*
!      * \c or \connect -- connect to database using the specified parameters.
!      *
!      * \c [-reuse-previous=BOOL] dbname user host port
!      *
!      * Specifying a parameter as '-' is equivalent to omitting it.  Examples:
!      *
!      * \c - - hst        Connect to current database on current port of host
!      * "hst" as current user. \c - usr - prt   Connect to current database on
!      * "prt" port of current host as user "usr". \c dbs              Connect to
!      * "dbs" database on current port of current host as current user.
!      */
!     else if (strcmp(cmd, "c") == 0 || strcmp(cmd, "connect") == 0)
      {
          static const char prefix[] = "-reuse-previous=";
          char       *opt1,
--- 457,488 ----
          success = do_pset("title", opt, &pset.popt, pset.quiet);
          free(opt);
      }
+     else
+         ignore_slash_options(scan_state);

!     return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
! }
!
! /*
!  * \c or \connect -- connect to database using the specified parameters.
!  *
!  * \c [-reuse-previous=BOOL] dbname user host port
!  *
!  * Specifying a parameter as '-' is equivalent to omitting it.  Examples:
!  *
!  * \c - - hst        Connect to current database on current port of
!  *                    host "hst" as current user.
!  * \c - usr - prt    Connect to current database on port "prt" of current host
!  *                    as user "usr".
!  * \c dbs            Connect to database "dbs" on current port of current host
!  *                    as current user.
!  */
! static backslashResult
! exec_command_connect(PsqlScanState scan_state, bool active_branch)
! {
!     bool        success = true;
!
!     if (active_branch)
      {
          static const char prefix[] = "-reuse-previous=";
          char       *opt1,
*************** exec_command(const char *cmd,
*** 277,285 ****
          }
          free(opt1);
      }

!     /* \cd */
!     else if (strcmp(cmd, "cd") == 0)
      {
          char       *opt = psql_scan_slash_option(scan_state,
                                                   OT_NORMAL, NULL, true);
--- 521,541 ----
          }
          free(opt1);
      }
+     else
+         ignore_slash_options(scan_state);

!     return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
! }
!
! /*
!  * \cd -- change directory
!  */
! static backslashResult
! exec_command_cd(PsqlScanState scan_state, bool active_branch, const char *cmd)
! {
!     bool        success = true;
!
!     if (active_branch)
      {
          char       *opt = psql_scan_slash_option(scan_state,
                                                   OT_NORMAL, NULL, true);
*************** exec_command(const char *cmd,
*** 323,331 ****
          if (opt)
              free(opt);
      }

!     /* \conninfo -- display information about the current connection */
!     else if (strcmp(cmd, "conninfo") == 0)
      {
          char       *db = PQdb(pset.db);

--- 579,597 ----
          if (opt)
              free(opt);
      }
+     else
+         ignore_slash_options(scan_state);

!     return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
! }
!
! /*
!  * \conninfo -- display information about the current connection
!  */
! static backslashResult
! exec_command_conninfo(PsqlScanState scan_state, bool active_branch)
! {
!     if (active_branch)
      {
          char       *db = PQdb(pset.db);

*************** exec_command(const char *cmd,
*** 366,373 ****
          }
      }

!     /* \copy */
!     else if (pg_strcasecmp(cmd, "copy") == 0)
      {
          char       *opt = psql_scan_slash_option(scan_state,
                                                   OT_WHOLE_LINE, NULL, false);
--- 632,649 ----
          }
      }

!     return PSQL_CMD_SKIP_LINE;
! }
!
! /*
!  * \copy -- run a COPY command
!  */
! static backslashResult
! exec_command_copy(PsqlScanState scan_state, bool active_branch)
! {
!     bool        success = true;
!
!     if (active_branch)
      {
          char       *opt = psql_scan_slash_option(scan_state,
                                                   OT_WHOLE_LINE, NULL, false);
*************** exec_command(const char *cmd,
*** 375,387 ****
          success = do_copy(opt);
          free(opt);
      }

!     /* \copyright */
!     else if (strcmp(cmd, "copyright") == 0)
          print_copyright();

!     /* \crosstabview -- execute a query and display results in crosstab */
!     else if (strcmp(cmd, "crosstabview") == 0)
      {
          int            i;

--- 651,683 ----
          success = do_copy(opt);
          free(opt);
      }
+     else
+         ignore_slash_whole_line(scan_state);

!     return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
! }
!
! /*
!  * \copyright
!  */
! static backslashResult
! exec_command_copyright(PsqlScanState scan_state, bool active_branch)
! {
!     if (active_branch)
          print_copyright();

!     return PSQL_CMD_SKIP_LINE;
! }
!
! /*
!  * \crosstabview -- execute a query and display results in crosstab
!  */
! static backslashResult
! exec_command_crosstabview(PsqlScanState scan_state, bool active_branch)
! {
!     backslashResult status = PSQL_CMD_SKIP_LINE;
!
!     if (active_branch)
      {
          int            i;

*************** exec_command(const char *cmd,
*** 391,399 ****
          pset.crosstab_flag = true;
          status = PSQL_CMD_SEND;
      }

!     /* \d* commands */
!     else if (cmd[0] == 'd')
      {
          char       *pattern;
          bool        show_verbose,
--- 687,708 ----
          pset.crosstab_flag = true;
          status = PSQL_CMD_SEND;
      }
+     else
+         ignore_slash_options(scan_state);

!     return status;
! }
!
! /*
!  * \d* commands
!  */
! static backslashResult
! exec_command_d(PsqlScanState scan_state, bool active_branch, const char *cmd)
! {
!     backslashResult status = PSQL_CMD_SKIP_LINE;
!     bool        success = true;
!
!     if (active_branch)
      {
          char       *pattern;
          bool        show_verbose,
*************** exec_command(const char *cmd,
*** 502,508 ****
                      success = listDbRoleSettings(pattern, pattern2);
                  }
                  else
!                     success = PSQL_CMD_UNKNOWN;
                  break;
              case 'R':
                  switch (cmd[2])
--- 811,817 ----
                      success = listDbRoleSettings(pattern, pattern2);
                  }
                  else
!                     status = PSQL_CMD_UNKNOWN;
                  break;
              case 'R':
                  switch (cmd[2])
*************** exec_command(const char *cmd,
*** 580,592 ****
          if (pattern)
              free(pattern);
      }


!     /*
!      * \e or \edit -- edit the current query buffer, or edit a file and make
!      * it the query buffer
!      */
!     else if (strcmp(cmd, "e") == 0 || strcmp(cmd, "edit") == 0)
      {
          if (!query_buf)
          {
--- 889,914 ----
          if (pattern)
              free(pattern);
      }
+     else
+         ignore_slash_options(scan_state);

+     if (!success)
+         status = PSQL_CMD_ERROR;

!     return status;
! }
!
! /*
!  * \e or \edit -- edit the current query buffer, or edit a file and
!  * make it the query buffer
!  */
! static backslashResult
! exec_command_edit(PsqlScanState scan_state, bool active_branch,
!                   PQExpBuffer query_buf, PQExpBuffer previous_buf)
! {
!     backslashResult status = PSQL_CMD_SKIP_LINE;
!
!     if (active_branch)
      {
          if (!query_buf)
          {
*************** exec_command(const char *cmd,
*** 632,637 ****
--- 954,963 ----
                  expand_tilde(&fname);
                  if (fname)
                      canonicalize_path(fname);
+
+                 /* Applies to previous query if current buffer is empty */
+                 copy_previous_query(query_buf, previous_buf);
+
                  if (do_edit(fname, query_buf, lineno, NULL))
                      status = PSQL_CMD_NEWEDIT;
                  else
*************** exec_command(const char *cmd,
*** 643,655 ****
                  free(ln);
          }
      }

!     /*
!      * \ef -- edit the named function, or present a blank CREATE FUNCTION
!      * template if no argument is given
!      */
!     else if (strcmp(cmd, "ef") == 0)
      {
          int            lineno = -1;

          if (pset.sversion < 80400)
--- 969,994 ----
                  free(ln);
          }
      }
+     else
+         ignore_slash_options(scan_state);

!     return status;
! }
!
! /*
!  * \ef -- edit the named function, or present a blank CREATE FUNCTION
!  * template if no argument is given
!  */
! static backslashResult
! exec_command_ef(PsqlScanState scan_state, bool active_branch,
!                 PQExpBuffer query_buf)
! {
!     backslashResult status = PSQL_CMD_SKIP_LINE;
!
!     if (active_branch)
      {
+         char       *func = psql_scan_slash_option(scan_state,
+                                                   OT_WHOLE_LINE, NULL, true);
          int            lineno = -1;

          if (pset.sversion < 80400)
*************** exec_command(const char *cmd,
*** 668,678 ****
          }
          else
          {
-             char       *func;
              Oid            foid = InvalidOid;

-             func = psql_scan_slash_option(scan_state,
-                                           OT_WHOLE_LINE, NULL, true);
              lineno = strip_lineno_from_objdesc(func);
              if (lineno == 0)
              {
--- 1007,1014 ----
*************** exec_command(const char *cmd,
*** 725,733 ****
                      lines++;
                  }
              }
-
-             if (func)
-                 free(func);
          }

          if (status != PSQL_CMD_ERROR)
--- 1061,1066 ----
*************** exec_command(const char *cmd,
*** 741,754 ****
              else
                  status = PSQL_CMD_NEWEDIT;
          }
      }

!     /*
!      * \ev -- edit the named view, or present a blank CREATE VIEW template if
!      * no argument is given
!      */
!     else if (strcmp(cmd, "ev") == 0)
      {
          int            lineno = -1;

          if (pset.sversion < 70400)
--- 1074,1103 ----
              else
                  status = PSQL_CMD_NEWEDIT;
          }
+
+         if (func)
+             free(func);
      }
+     else
+         ignore_slash_whole_line(scan_state);

!     return status;
! }
!
! /*
!  * \ev -- edit the named view, or present a blank CREATE VIEW
!  * template if no argument is given
!  */
! static backslashResult
! exec_command_ev(PsqlScanState scan_state, bool active_branch,
!                 PQExpBuffer query_buf)
! {
!     backslashResult status = PSQL_CMD_SKIP_LINE;
!
!     if (active_branch)
      {
+         char       *view = psql_scan_slash_option(scan_state,
+                                                   OT_WHOLE_LINE, NULL, true);
          int            lineno = -1;

          if (pset.sversion < 70400)
*************** exec_command(const char *cmd,
*** 767,777 ****
          }
          else
          {
-             char       *view;
              Oid            view_oid = InvalidOid;

-             view = psql_scan_slash_option(scan_state,
-                                           OT_WHOLE_LINE, NULL, true);
              lineno = strip_lineno_from_objdesc(view);
              if (lineno == 0)
              {
--- 1116,1123 ----
*************** exec_command(const char *cmd,
*** 796,804 ****
                  /* error already reported */
                  status = PSQL_CMD_ERROR;
              }
-
-             if (view)
-                 free(view);
          }

          if (status != PSQL_CMD_ERROR)
--- 1142,1147 ----
*************** exec_command(const char *cmd,
*** 812,821 ****
              else
                  status = PSQL_CMD_NEWEDIT;
          }
      }

!     /* \echo and \qecho */
!     else if (strcmp(cmd, "echo") == 0 || strcmp(cmd, "qecho") == 0)
      {
          char       *value;
          char        quoted;
--- 1155,1177 ----
              else
                  status = PSQL_CMD_NEWEDIT;
          }
+
+         if (view)
+             free(view);
      }
+     else
+         ignore_slash_whole_line(scan_state);

!     return status;
! }
!
! /*
!  * \echo and \qecho -- echo arguments to stdout or query output
!  */
! static backslashResult
! exec_command_echo(PsqlScanState scan_state, bool active_branch, const char *cmd)
! {
!     if (active_branch)
      {
          char       *value;
          char        quoted;
*************** exec_command(const char *cmd,
*** 846,854 ****
          if (!no_newline)
              fputs("\n", fout);
      }

!     /* \encoding -- set/show client side encoding */
!     else if (strcmp(cmd, "encoding") == 0)
      {
          char       *encoding = psql_scan_slash_option(scan_state,
                                                        OT_NORMAL, NULL, false);
--- 1202,1220 ----
          if (!no_newline)
              fputs("\n", fout);
      }
+     else
+         ignore_slash_options(scan_state);

!     return PSQL_CMD_SKIP_LINE;
! }
!
! /*
!  * \encoding -- set/show client side encoding
!  */
! static backslashResult
! exec_command_encoding(PsqlScanState scan_state, bool active_branch)
! {
!     if (active_branch)
      {
          char       *encoding = psql_scan_slash_option(scan_state,
                                                        OT_NORMAL, NULL, false);
*************** exec_command(const char *cmd,
*** 874,882 ****
              free(encoding);
          }
      }

!     /* \errverbose -- display verbose message from last failed query */
!     else if (strcmp(cmd, "errverbose") == 0)
      {
          if (pset.last_error_result)
          {
--- 1240,1258 ----
              free(encoding);
          }
      }
+     else
+         ignore_slash_options(scan_state);

!     return PSQL_CMD_SKIP_LINE;
! }
!
! /*
!  * \errverbose -- display verbose message from last failed query
!  */
! static backslashResult
! exec_command_errverbose(PsqlScanState scan_state, bool active_branch)
! {
!     if (active_branch)
      {
          if (pset.last_error_result)
          {
*************** exec_command(const char *cmd,
*** 897,904 ****
              puts(_("There is no previous error."));
      }

!     /* \f -- change field separator */
!     else if (strcmp(cmd, "f") == 0)
      {
          char       *fname = psql_scan_slash_option(scan_state,
                                                     OT_NORMAL, NULL, false);
--- 1273,1290 ----
              puts(_("There is no previous error."));
      }

!     return PSQL_CMD_SKIP_LINE;
! }
!
! /*
!  * \f -- change field separator
!  */
! static backslashResult
! exec_command_f(PsqlScanState scan_state, bool active_branch)
! {
!     bool        success = true;
!
!     if (active_branch)
      {
          char       *fname = psql_scan_slash_option(scan_state,
                                                     OT_NORMAL, NULL, false);
*************** exec_command(const char *cmd,
*** 906,917 ****
          success = do_pset("fieldsep", fname, &pset.popt, pset.quiet);
          free(fname);
      }

!     /*
!      * \g [filename] -- send query, optionally with output to file/pipe
!      * \gx [filename] -- same as \g, with expanded mode forced
!      */
!     else if (strcmp(cmd, "g") == 0 || strcmp(cmd, "gx") == 0)
      {
          char       *fname = psql_scan_slash_option(scan_state,
                                                     OT_FILEPIPE, NULL, false);
--- 1292,1313 ----
          success = do_pset("fieldsep", fname, &pset.popt, pset.quiet);
          free(fname);
      }
+     else
+         ignore_slash_options(scan_state);

!     return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
! }
!
! /*
!  * \g [filename] -- send query, optionally with output to file/pipe
!  * \gx [filename] -- same as \g, with expanded mode forced
!  */
! static backslashResult
! exec_command_g(PsqlScanState scan_state, bool active_branch, const char *cmd)
! {
!     backslashResult status = PSQL_CMD_SKIP_LINE;
!
!     if (active_branch)
      {
          char       *fname = psql_scan_slash_option(scan_state,
                                                     OT_FILEPIPE, NULL, false);
*************** exec_command(const char *cmd,
*** 928,943 ****
              pset.g_expanded = true;
          status = PSQL_CMD_SEND;
      }

!     /* \gexec -- send query and execute each field of result */
!     else if (strcmp(cmd, "gexec") == 0)
      {
          pset.gexec_flag = true;
          status = PSQL_CMD_SEND;
      }

!     /* \gset [prefix] -- send query and store result into variables */
!     else if (strcmp(cmd, "gset") == 0)
      {
          char       *prefix = psql_scan_slash_option(scan_state,
                                                      OT_NORMAL, NULL, false);
--- 1324,1361 ----
              pset.g_expanded = true;
          status = PSQL_CMD_SEND;
      }
+     else
+         ignore_slash_filepipe(scan_state);

!     return status;
! }
!
! /*
!  * \gexec -- send query and execute each field of result
!  */
! static backslashResult
! exec_command_gexec(PsqlScanState scan_state, bool active_branch)
! {
!     backslashResult status = PSQL_CMD_SKIP_LINE;
!
!     if (active_branch)
      {
          pset.gexec_flag = true;
          status = PSQL_CMD_SEND;
      }

!     return status;
! }
!
! /*
!  * \gset [prefix] -- send query and store result into variables
!  */
! static backslashResult
! exec_command_gset(PsqlScanState scan_state, bool active_branch)
! {
!     backslashResult status = PSQL_CMD_SKIP_LINE;
!
!     if (active_branch)
      {
          char       *prefix = psql_scan_slash_option(scan_state,
                                                      OT_NORMAL, NULL, false);
*************** exec_command(const char *cmd,
*** 952,960 ****
          /* gset_prefix is freed later */
          status = PSQL_CMD_SEND;
      }

!     /* help */
!     else if (strcmp(cmd, "h") == 0 || strcmp(cmd, "help") == 0)
      {
          char       *opt = psql_scan_slash_option(scan_state,
                                                   OT_WHOLE_LINE, NULL, false);
--- 1370,1388 ----
          /* gset_prefix is freed later */
          status = PSQL_CMD_SEND;
      }
+     else
+         ignore_slash_options(scan_state);

!     return status;
! }
!
! /*
!  * \help [topic] -- print help about SQL commands
!  */
! static backslashResult
! exec_command_help(PsqlScanState scan_state, bool active_branch)
! {
!     if (active_branch)
      {
          char       *opt = psql_scan_slash_option(scan_state,
                                                   OT_WHOLE_LINE, NULL, false);
*************** exec_command(const char *cmd,
*** 973,981 ****
          helpSQL(opt, pset.popt.topt.pager);
          free(opt);
      }

!     /* HTML mode */
!     else if (strcmp(cmd, "H") == 0 || strcmp(cmd, "html") == 0)
      {
          if (pset.popt.topt.format != PRINT_HTML)
              success = do_pset("format", "html", &pset.popt, pset.quiet);
--- 1401,1421 ----
          helpSQL(opt, pset.popt.topt.pager);
          free(opt);
      }
+     else
+         ignore_slash_whole_line(scan_state);

!     return PSQL_CMD_SKIP_LINE;
! }
!
! /*
!  * \H and \html -- toggle HTML formatting
!  */
! static backslashResult
! exec_command_html(PsqlScanState scan_state, bool active_branch)
! {
!     bool        success = true;
!
!     if (active_branch)
      {
          if (pset.popt.topt.format != PRINT_HTML)
              success = do_pset("format", "html", &pset.popt, pset.quiet);
*************** exec_command(const char *cmd,
*** 983,992 ****
              success = do_pset("format", "aligned", &pset.popt, pset.quiet);
      }


!     /* \i and \ir include files */
!     else if (strcmp(cmd, "i") == 0 || strcmp(cmd, "include") == 0
!            || strcmp(cmd, "ir") == 0 || strcmp(cmd, "include_relative") == 0)
      {
          char       *fname = psql_scan_slash_option(scan_state,
                                                     OT_NORMAL, NULL, true);
--- 1423,1440 ----
              success = do_pset("format", "aligned", &pset.popt, pset.quiet);
      }

+     return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
+ }

! /*
!  * \i and \ir -- include a file
!  */
! static backslashResult
! exec_command_include(PsqlScanState scan_state, bool active_branch, const char *cmd)
! {
!     bool        success = true;
!
!     if (active_branch)
      {
          char       *fname = psql_scan_slash_option(scan_state,
                                                     OT_NORMAL, NULL, true);
*************** exec_command(const char *cmd,
*** 1007,1016 ****
              free(fname);
          }
      }

!     /* \l is list databases */
!     else if (strcmp(cmd, "l") == 0 || strcmp(cmd, "list") == 0 ||
!              strcmp(cmd, "l+") == 0 || strcmp(cmd, "list+") == 0)
      {
          char       *pattern;
          bool        show_verbose;
--- 1455,1708 ----
              free(fname);
          }
      }
+     else
+         ignore_slash_options(scan_state);

!     return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
! }
!
! /*
!  * \if <expr> -- beginning of an \if..\endif block
!  *
!  * <expr> is parsed as a boolean expression.  Invalid expressions will emit a
!  * warning and be treated as false.  Statements that follow a false expression
!  * will be parsed but ignored.  Note that in the case where an \if statement
!  * is itself within an inactive section of a block, then the entire inner
!  * \if..\endif block will be parsed but ignored.
!  */
! static backslashResult
! exec_command_if(PsqlScanState scan_state, ConditionalStack cstack,
!                 PQExpBuffer query_buf)
! {
!     if (conditional_active(cstack))
!     {
!         /*
!          * First, push a new active stack entry; this ensures that the lexer
!          * will perform variable substitution and backtick evaluation while
!          * scanning the expression.  (That should happen anyway, since we know
!          * we're in an active outer branch, but let's be sure.)
!          */
!         conditional_stack_push(cstack, IFSTATE_TRUE);
!
!         /* Remember current query state in case we need to restore later */
!         save_query_text_state(scan_state, cstack, query_buf);
!
!         /*
!          * Evaluate the expression; if it's false, change to inactive state.
!          */
!         if (!is_true_boolean_expression(scan_state, "\\if expression"))
!             conditional_stack_poke(cstack, IFSTATE_FALSE);
!     }
!     else
!     {
!         /*
!          * We're within an inactive outer branch, so this entire \if block
!          * will be ignored.  We don't want to evaluate the expression, so push
!          * the "ignored" stack state before scanning it.
!          */
!         conditional_stack_push(cstack, IFSTATE_IGNORED);
!
!         /* Remember current query state in case we need to restore later */
!         save_query_text_state(scan_state, cstack, query_buf);
!
!         ignore_boolean_expression(scan_state);
!     }
!
!     return PSQL_CMD_SKIP_LINE;
! }
!
! /*
!  * \elif <expr> -- alternative branch in an \if..\endif block
!  *
!  * <expr> is evaluated the same as in \if <expr>.
!  */
! static backslashResult
! exec_command_elif(PsqlScanState scan_state, ConditionalStack cstack,
!                   PQExpBuffer query_buf)
! {
!     bool        success = true;
!
!     switch (conditional_stack_peek(cstack))
!     {
!         case IFSTATE_TRUE:
!
!             /*
!              * Just finished active branch of this \if block.  Update saved
!              * state so we will keep whatever data was put in query_buf by the
!              * active branch.
!              */
!             save_query_text_state(scan_state, cstack, query_buf);
!
!             /*
!              * Discard \elif expression and ignore the rest until \endif.
!              * Switch state before reading expression to ensure proper lexer
!              * behavior.
!              */
!             conditional_stack_poke(cstack, IFSTATE_IGNORED);
!             ignore_boolean_expression(scan_state);
!             break;
!         case IFSTATE_FALSE:
!
!             /*
!              * Discard any query text added by the just-skipped branch.
!              */
!             discard_query_text(scan_state, cstack, query_buf);
!
!             /*
!              * Have not yet found a true expression in this \if block, so this
!              * might be the first.  We have to change state before examining
!              * the expression, or the lexer won't do the right thing.
!              */
!             conditional_stack_poke(cstack, IFSTATE_TRUE);
!             if (!is_true_boolean_expression(scan_state, "\\elif expression"))
!                 conditional_stack_poke(cstack, IFSTATE_FALSE);
!             break;
!         case IFSTATE_IGNORED:
!
!             /*
!              * Discard any query text added by the just-skipped branch.
!              */
!             discard_query_text(scan_state, cstack, query_buf);
!
!             /*
!              * Skip expression and move on.  Either the \if block already had
!              * an active section, or whole block is being skipped.
!              */
!             ignore_boolean_expression(scan_state);
!             break;
!         case IFSTATE_ELSE_TRUE:
!         case IFSTATE_ELSE_FALSE:
!             psql_error("\\elif: cannot occur after \\else\n");
!             success = false;
!             break;
!         case IFSTATE_NONE:
!             /* no \if to elif from */
!             psql_error("\\elif: no matching \\if\n");
!             success = false;
!             break;
!     }
!
!     return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
! }
!
! /*
!  * \else -- final alternative in an \if..\endif block
!  *
!  * Statements within an \else branch will only be executed if
!  * all previous \if and \elif expressions evaluated to false
!  * and the block was not itself being ignored.
!  */
! static backslashResult
! exec_command_else(PsqlScanState scan_state, ConditionalStack cstack,
!                   PQExpBuffer query_buf)
! {
!     bool        success = true;
!
!     switch (conditional_stack_peek(cstack))
!     {
!         case IFSTATE_TRUE:
!
!             /*
!              * Just finished active branch of this \if block.  Update saved
!              * state so we will keep whatever data was put in query_buf by the
!              * active branch.
!              */
!             save_query_text_state(scan_state, cstack, query_buf);
!
!             /* Now skip the \else branch */
!             conditional_stack_poke(cstack, IFSTATE_ELSE_FALSE);
!             break;
!         case IFSTATE_FALSE:
!
!             /*
!              * Discard any query text added by the just-skipped branch.
!              */
!             discard_query_text(scan_state, cstack, query_buf);
!
!             /*
!              * We've not found any true \if or \elif expression, so execute
!              * the \else branch.
!              */
!             conditional_stack_poke(cstack, IFSTATE_ELSE_TRUE);
!             break;
!         case IFSTATE_IGNORED:
!
!             /*
!              * Discard any query text added by the just-skipped branch.
!              */
!             discard_query_text(scan_state, cstack, query_buf);
!
!             /*
!              * Either we previously processed the active branch of this \if,
!              * or the whole \if block is being skipped.  Either way, skip the
!              * \else branch.
!              */
!             conditional_stack_poke(cstack, IFSTATE_ELSE_FALSE);
!             break;
!         case IFSTATE_ELSE_TRUE:
!         case IFSTATE_ELSE_FALSE:
!             psql_error("\\else: cannot occur after \\else\n");
!             success = false;
!             break;
!         case IFSTATE_NONE:
!             /* no \if to else from */
!             psql_error("\\else: no matching \\if\n");
!             success = false;
!             break;
!     }
!
!     return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
! }
!
! /*
!  * \endif -- ends an \if...\endif block
!  */
! static backslashResult
! exec_command_endif(PsqlScanState scan_state, ConditionalStack cstack,
!                    PQExpBuffer query_buf)
! {
!     bool        success = true;
!
!     switch (conditional_stack_peek(cstack))
!     {
!         case IFSTATE_TRUE:
!         case IFSTATE_ELSE_TRUE:
!             /* Close the \if block, keeping the query text */
!             success = conditional_stack_pop(cstack);
!             Assert(success);
!             break;
!         case IFSTATE_FALSE:
!         case IFSTATE_IGNORED:
!         case IFSTATE_ELSE_FALSE:
!
!             /*
!              * Discard any query text added by the just-skipped branch.
!              */
!             discard_query_text(scan_state, cstack, query_buf);
!
!             /* Close the \if block */
!             success = conditional_stack_pop(cstack);
!             Assert(success);
!             break;
!         case IFSTATE_NONE:
!             /* no \if to end */
!             psql_error("\\endif: no matching \\if\n");
!             success = false;
!             break;
!     }
!
!     return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
! }
!
! /*
!  * \l -- list databases
!  */
! static backslashResult
! exec_command_list(PsqlScanState scan_state, bool active_branch, const char *cmd)
! {
!     bool        success = true;
!
!     if (active_branch)
      {
          char       *pattern;
          bool        show_verbose;
*************** exec_command(const char *cmd,
*** 1025,1035 ****
          if (pattern)
              free(pattern);
      }

!     /*
!      * large object things
!      */
!     else if (strncmp(cmd, "lo_", 3) == 0)
      {
          char       *opt1,
                     *opt2;
--- 1717,1738 ----
          if (pattern)
              free(pattern);
      }
+     else
+         ignore_slash_options(scan_state);

!     return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
! }
!
! /*
!  * \lo_* -- large object operations
!  */
! static backslashResult
! exec_command_lo(PsqlScanState scan_state, bool active_branch, const char *cmd)
! {
!     backslashResult status = PSQL_CMD_SKIP_LINE;
!     bool        success = true;
!
!     if (active_branch)
      {
          char       *opt1,
                     *opt2;
*************** exec_command(const char *cmd,
*** 1087,1096 ****
          free(opt1);
          free(opt2);
      }


!     /* \o -- set query output */
!     else if (strcmp(cmd, "o") == 0 || strcmp(cmd, "out") == 0)
      {
          char       *fname = psql_scan_slash_option(scan_state,
                                                     OT_FILEPIPE, NULL, true);
--- 1790,1813 ----
          free(opt1);
          free(opt2);
      }
+     else
+         ignore_slash_options(scan_state);

+     if (!success)
+         status = PSQL_CMD_ERROR;

!     return status;
! }
!
! /*
!  * \o -- set query output
!  */
! static backslashResult
! exec_command_out(PsqlScanState scan_state, bool active_branch)
! {
!     bool        success = true;
!
!     if (active_branch)
      {
          char       *fname = psql_scan_slash_option(scan_state,
                                                     OT_FILEPIPE, NULL, true);
*************** exec_command(const char *cmd,
*** 1099,1107 ****
          success = setQFout(fname);
          free(fname);
      }

!     /* \p prints the current query buffer */
!     else if (strcmp(cmd, "p") == 0 || strcmp(cmd, "print") == 0)
      {
          if (query_buf && query_buf->len > 0)
              puts(query_buf->data);
--- 1816,1835 ----
          success = setQFout(fname);
          free(fname);
      }
+     else
+         ignore_slash_filepipe(scan_state);

!     return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
! }
!
! /*
!  * \p -- print the current query buffer
!  */
! static backslashResult
! exec_command_print(PsqlScanState scan_state, bool active_branch,
!                    PQExpBuffer query_buf)
! {
!     if (active_branch)
      {
          if (query_buf && query_buf->len > 0)
              puts(query_buf->data);
*************** exec_command(const char *cmd,
*** 1110,1118 ****
          fflush(stdout);
      }

!     /* \password -- set user password */
!     else if (strcmp(cmd, "password") == 0)
      {
          char        pw1[100];
          char        pw2[100];

--- 1838,1858 ----
          fflush(stdout);
      }

!     return PSQL_CMD_SKIP_LINE;
! }
!
! /*
!  * \password -- set user password
!  */
! static backslashResult
! exec_command_password(PsqlScanState scan_state, bool active_branch)
! {
!     bool        success = true;
!
!     if (active_branch)
      {
+         char       *opt0 = psql_scan_slash_option(scan_state,
+                                                   OT_SQLID, NULL, true);
          char        pw1[100];
          char        pw2[100];

*************** exec_command(const char *cmd,
*** 1126,1132 ****
          }
          else
          {
-             char       *opt0 = psql_scan_slash_option(scan_state, OT_SQLID, NULL, true);
              char       *user;
              char       *encrypted_password;

--- 1866,1871 ----
*************** exec_command(const char *cmd,
*** 1159,1172 ****
                      PQclear(res);
                  PQfreemem(encrypted_password);
              }
-
-             if (opt0)
-                 free(opt0);
          }
      }

!     /* \prompt -- prompt and set variable */
!     else if (strcmp(cmd, "prompt") == 0)
      {
          char       *opt,
                     *prompt_text = NULL;
--- 1898,1924 ----
                      PQclear(res);
                  PQfreemem(encrypted_password);
              }
          }
+
+         if (opt0)
+             free(opt0);
      }
+     else
+         ignore_slash_options(scan_state);

!     return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
! }
!
! /*
!  * \prompt -- prompt and set variable
!  */
! static backslashResult
! exec_command_prompt(PsqlScanState scan_state, bool active_branch,
!                     const char *cmd)
! {
!     bool        success = true;
!
!     if (active_branch)
      {
          char       *opt,
                     *prompt_text = NULL;
*************** exec_command(const char *cmd,
*** 1225,1233 ****
              free(opt);
          }
      }

!     /* \pset -- set printing parameters */
!     else if (strcmp(cmd, "pset") == 0)
      {
          char       *opt0 = psql_scan_slash_option(scan_state,
                                                    OT_NORMAL, NULL, false);
--- 1977,1997 ----
              free(opt);
          }
      }
+     else
+         ignore_slash_options(scan_state);

!     return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
! }
!
! /*
!  * \pset -- set printing parameters
!  */
! static backslashResult
! exec_command_pset(PsqlScanState scan_state, bool active_branch)
! {
!     bool        success = true;
!
!     if (active_branch)
      {
          char       *opt0 = psql_scan_slash_option(scan_state,
                                                    OT_NORMAL, NULL, false);
*************** exec_command(const char *cmd,
*** 1267,1279 ****
          free(opt0);
          free(opt1);
      }

!     /* \q or \quit */
!     else if (strcmp(cmd, "q") == 0 || strcmp(cmd, "quit") == 0)
          status = PSQL_CMD_TERMINATE;

!     /* reset(clear) the buffer */
!     else if (strcmp(cmd, "r") == 0 || strcmp(cmd, "reset") == 0)
      {
          resetPQExpBuffer(query_buf);
          psql_scan_reset(scan_state);
--- 2031,2064 ----
          free(opt0);
          free(opt1);
      }
+     else
+         ignore_slash_options(scan_state);

!     return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
! }
!
! /*
!  * \q or \quit -- exit psql
!  */
! static backslashResult
! exec_command_quit(PsqlScanState scan_state, bool active_branch)
! {
!     backslashResult status = PSQL_CMD_SKIP_LINE;
!
!     if (active_branch)
          status = PSQL_CMD_TERMINATE;

!     return status;
! }
!
! /*
!  * \r -- reset (clear) the query buffer
!  */
! static backslashResult
! exec_command_reset(PsqlScanState scan_state, bool active_branch,
!                    PQExpBuffer query_buf)
! {
!     if (active_branch)
      {
          resetPQExpBuffer(query_buf);
          psql_scan_reset(scan_state);
*************** exec_command(const char *cmd,
*** 1281,1288 ****
              puts(_("Query buffer reset (cleared)."));
      }

!     /* \s save history in a file or show it on the screen */
!     else if (strcmp(cmd, "s") == 0)
      {
          char       *fname = psql_scan_slash_option(scan_state,
                                                     OT_NORMAL, NULL, true);
--- 2066,2083 ----
              puts(_("Query buffer reset (cleared)."));
      }

!     return PSQL_CMD_SKIP_LINE;
! }
!
! /*
!  * \s -- save history in a file or show it on the screen
!  */
! static backslashResult
! exec_command_s(PsqlScanState scan_state, bool active_branch)
! {
!     bool        success = true;
!
!     if (active_branch)
      {
          char       *fname = psql_scan_slash_option(scan_state,
                                                     OT_NORMAL, NULL, true);
*************** exec_command(const char *cmd,
*** 1295,1303 ****
              putchar('\n');
          free(fname);
      }

!     /* \set -- generalized set variable/option command */
!     else if (strcmp(cmd, "set") == 0)
      {
          char       *opt0 = psql_scan_slash_option(scan_state,
                                                    OT_NORMAL, NULL, false);
--- 2090,2110 ----
              putchar('\n');
          free(fname);
      }
+     else
+         ignore_slash_options(scan_state);

!     return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
! }
!
! /*
!  * \set -- set variable
!  */
! static backslashResult
! exec_command_set(PsqlScanState scan_state, bool active_branch)
! {
!     bool        success = true;
!
!     if (active_branch)
      {
          char       *opt0 = psql_scan_slash_option(scan_state,
                                                    OT_NORMAL, NULL, false);
*************** exec_command(const char *cmd,
*** 1336,1345 ****
          }
          free(opt0);
      }


!     /* \setenv -- set environment command */
!     else if (strcmp(cmd, "setenv") == 0)
      {
          char       *envvar = psql_scan_slash_option(scan_state,
                                                      OT_NORMAL, NULL, false);
--- 2143,2164 ----
          }
          free(opt0);
      }
+     else
+         ignore_slash_options(scan_state);

+     return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
+ }

! /*
!  * \setenv -- set environment variable
!  */
! static backslashResult
! exec_command_setenv(PsqlScanState scan_state, bool active_branch,
!                     const char *cmd)
! {
!     bool        success = true;
!
!     if (active_branch)
      {
          char       *envvar = psql_scan_slash_option(scan_state,
                                                      OT_NORMAL, NULL, false);
*************** exec_command(const char *cmd,
*** 1381,1389 ****
          free(envvar);
          free(envval);
      }

!     /* \sf -- show a function's source code */
!     else if (strcmp(cmd, "sf") == 0 || strcmp(cmd, "sf+") == 0)
      {
          bool        show_linenumbers = (strcmp(cmd, "sf+") == 0);
          PQExpBuffer func_buf;
--- 2200,2220 ----
          free(envvar);
          free(envval);
      }
+     else
+         ignore_slash_options(scan_state);

!     return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
! }
!
! /*
!  * \sf -- show a function's source code
!  */
! static backslashResult
! exec_command_sf(PsqlScanState scan_state, bool active_branch, const char *cmd)
! {
!     backslashResult status = PSQL_CMD_SKIP_LINE;
!
!     if (active_branch)
      {
          bool        show_linenumbers = (strcmp(cmd, "sf+") == 0);
          PQExpBuffer func_buf;
*************** exec_command(const char *cmd,
*** 1463,1471 ****
              free(func);
          destroyPQExpBuffer(func_buf);
      }

!     /* \sv -- show a view's source code */
!     else if (strcmp(cmd, "sv") == 0 || strcmp(cmd, "sv+") == 0)
      {
          bool        show_linenumbers = (strcmp(cmd, "sv+") == 0);
          PQExpBuffer view_buf;
--- 2294,2314 ----
              free(func);
          destroyPQExpBuffer(func_buf);
      }
+     else
+         ignore_slash_whole_line(scan_state);

!     return status;
! }
!
! /*
!  * \sv -- show a view's source code
!  */
! static backslashResult
! exec_command_sv(PsqlScanState scan_state, bool active_branch, const char *cmd)
! {
!     backslashResult status = PSQL_CMD_SKIP_LINE;
!
!     if (active_branch)
      {
          bool        show_linenumbers = (strcmp(cmd, "sv+") == 0);
          PQExpBuffer view_buf;
*************** exec_command(const char *cmd,
*** 1539,1547 ****
              free(view);
          destroyPQExpBuffer(view_buf);
      }

!     /* \t -- turn off headers and row count */
!     else if (strcmp(cmd, "t") == 0)
      {
          char       *opt = psql_scan_slash_option(scan_state,
                                                   OT_NORMAL, NULL, true);
--- 2382,2402 ----
              free(view);
          destroyPQExpBuffer(view_buf);
      }
+     else
+         ignore_slash_whole_line(scan_state);

!     return status;
! }
!
! /*
!  * \t -- turn off table headers and row count
!  */
! static backslashResult
! exec_command_t(PsqlScanState scan_state, bool active_branch)
! {
!     bool        success = true;
!
!     if (active_branch)
      {
          char       *opt = psql_scan_slash_option(scan_state,
                                                   OT_NORMAL, NULL, true);
*************** exec_command(const char *cmd,
*** 1549,1557 ****
          success = do_pset("tuples_only", opt, &pset.popt, pset.quiet);
          free(opt);
      }

!     /* \T -- define html <table ...> attributes */
!     else if (strcmp(cmd, "T") == 0)
      {
          char       *value = psql_scan_slash_option(scan_state,
                                                     OT_NORMAL, NULL, false);
--- 2404,2424 ----
          success = do_pset("tuples_only", opt, &pset.popt, pset.quiet);
          free(opt);
      }
+     else
+         ignore_slash_options(scan_state);

!     return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
! }
!
! /*
!  * \T -- define html <table ...> attributes
!  */
! static backslashResult
! exec_command_T(PsqlScanState scan_state, bool active_branch)
! {
!     bool        success = true;
!
!     if (active_branch)
      {
          char       *value = psql_scan_slash_option(scan_state,
                                                     OT_NORMAL, NULL, false);
*************** exec_command(const char *cmd,
*** 1559,1567 ****
          success = do_pset("tableattr", value, &pset.popt, pset.quiet);
          free(value);
      }

!     /* \timing -- toggle timing of queries */
!     else if (strcmp(cmd, "timing") == 0)
      {
          char       *opt = psql_scan_slash_option(scan_state,
                                                   OT_NORMAL, NULL, false);
--- 2426,2446 ----
          success = do_pset("tableattr", value, &pset.popt, pset.quiet);
          free(value);
      }
+     else
+         ignore_slash_options(scan_state);

!     return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
! }
!
! /*
!  * \timing -- enable/disable timing of queries
!  */
! static backslashResult
! exec_command_timing(PsqlScanState scan_state, bool active_branch)
! {
!     bool        success = true;
!
!     if (active_branch)
      {
          char       *opt = psql_scan_slash_option(scan_state,
                                                   OT_NORMAL, NULL, false);
*************** exec_command(const char *cmd,
*** 1579,1587 ****
          }
          free(opt);
      }

!     /* \unset */
!     else if (strcmp(cmd, "unset") == 0)
      {
          char       *opt = psql_scan_slash_option(scan_state,
                                                   OT_NORMAL, NULL, false);
--- 2458,2479 ----
          }
          free(opt);
      }
+     else
+         ignore_slash_options(scan_state);

!     return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
! }
!
! /*
!  * \unset -- unset variable
!  */
! static backslashResult
! exec_command_unset(PsqlScanState scan_state, bool active_branch,
!                    const char *cmd)
! {
!     bool        success = true;
!
!     if (active_branch)
      {
          char       *opt = psql_scan_slash_option(scan_state,
                                                   OT_NORMAL, NULL, false);
*************** exec_command(const char *cmd,
*** 1596,1608 ****

          free(opt);
      }

!     /* \w -- write query buffer to file */
!     else if (strcmp(cmd, "w") == 0 || strcmp(cmd, "write") == 0)
      {
          FILE       *fd = NULL;
          bool        is_pipe = false;
-         char       *fname = NULL;

          if (!query_buf)
          {
--- 2488,2515 ----

          free(opt);
      }
+     else
+         ignore_slash_options(scan_state);

!     return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
! }
!
! /*
!  * \w -- write query buffer to file
!  */
! static backslashResult
! exec_command_write(PsqlScanState scan_state, bool active_branch,
!                    const char *cmd,
!                    PQExpBuffer query_buf, PQExpBuffer previous_buf)
! {
!     backslashResult status = PSQL_CMD_SKIP_LINE;
!
!     if (active_branch)
      {
+         char       *fname = psql_scan_slash_option(scan_state,
+                                                    OT_FILEPIPE, NULL, true);
          FILE       *fd = NULL;
          bool        is_pipe = false;

          if (!query_buf)
          {
*************** exec_command(const char *cmd,
*** 1611,1627 ****
          }
          else
          {
-             fname = psql_scan_slash_option(scan_state,
-                                            OT_FILEPIPE, NULL, true);
-             expand_tilde(&fname);
-
              if (!fname)
              {
                  psql_error("\\%s: missing required argument\n", cmd);
!                 success = false;
              }
              else
              {
                  if (fname[0] == '|')
                  {
                      is_pipe = true;
--- 2518,2531 ----
          }
          else
          {
              if (!fname)
              {
                  psql_error("\\%s: missing required argument\n", cmd);
!                 status = PSQL_CMD_ERROR;
              }
              else
              {
+                 expand_tilde(&fname);
                  if (fname[0] == '|')
                  {
                      is_pipe = true;
*************** exec_command(const char *cmd,
*** 1636,1642 ****
                  if (!fd)
                  {
                      psql_error("%s: %s\n", fname, strerror(errno));
!                     success = false;
                  }
              }
          }
--- 2540,2546 ----
                  if (!fd)
                  {
                      psql_error("%s: %s\n", fname, strerror(errno));
!                     status = PSQL_CMD_ERROR;
                  }
              }
          }
*************** exec_command(const char *cmd,
*** 1647,1652 ****
--- 2551,2559 ----

              if (query_buf && query_buf->len > 0)
                  fprintf(fd, "%s\n", query_buf->data);
+             /* Applies to previous query if current buffer is empty */
+             else if (previous_buf && previous_buf->len > 0)
+                 fprintf(fd, "%s\n", previous_buf->data);

              if (is_pipe)
                  result = pclose(fd);
*************** exec_command(const char *cmd,
*** 1656,1662 ****
              if (result == EOF)
              {
                  psql_error("%s: %s\n", fname, strerror(errno));
!                 success = false;
              }
          }

--- 2563,2569 ----
              if (result == EOF)
              {
                  psql_error("%s: %s\n", fname, strerror(errno));
!                 status = PSQL_CMD_ERROR;
              }
          }

*************** exec_command(const char *cmd,
*** 1665,1673 ****

          free(fname);
      }

!     /* \watch -- execute a query every N seconds */
!     else if (strcmp(cmd, "watch") == 0)
      {
          char       *opt = psql_scan_slash_option(scan_state,
                                                   OT_NORMAL, NULL, true);
--- 2572,2593 ----

          free(fname);
      }
+     else
+         ignore_slash_filepipe(scan_state);

!     return status;
! }
!
! /*
!  * \watch -- execute a query every N seconds
!  */
! static backslashResult
! exec_command_watch(PsqlScanState scan_state, bool active_branch,
!                    PQExpBuffer query_buf, PQExpBuffer previous_buf)
! {
!     bool        success = true;
!
!     if (active_branch)
      {
          char       *opt = psql_scan_slash_option(scan_state,
                                                   OT_NORMAL, NULL, true);
*************** exec_command(const char *cmd,
*** 1682,1696 ****
              free(opt);
          }

          success = do_watch(query_buf, sleep);

          /* Reset the query buffer as though for \r */
          resetPQExpBuffer(query_buf);
          psql_scan_reset(scan_state);
      }

!     /* \x -- set or toggle expanded table representation */
!     else if (strcmp(cmd, "x") == 0)
      {
          char       *opt = psql_scan_slash_option(scan_state,
                                                   OT_NORMAL, NULL, true);
--- 2602,2631 ----
              free(opt);
          }

+         /* Applies to previous query if current buffer is empty */
+         copy_previous_query(query_buf, previous_buf);
+
          success = do_watch(query_buf, sleep);

          /* Reset the query buffer as though for \r */
          resetPQExpBuffer(query_buf);
          psql_scan_reset(scan_state);
      }
+     else
+         ignore_slash_options(scan_state);

!     return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
! }
!
! /*
!  * \x -- set or toggle expanded table representation
!  */
! static backslashResult
! exec_command_x(PsqlScanState scan_state, bool active_branch)
! {
!     bool        success = true;
!
!     if (active_branch)
      {
          char       *opt = psql_scan_slash_option(scan_state,
                                                   OT_NORMAL, NULL, true);
*************** exec_command(const char *cmd,
*** 1698,1706 ****
          success = do_pset("expanded", opt, &pset.popt, pset.quiet);
          free(opt);
      }

!     /* \z -- list table rights (equivalent to \dp) */
!     else if (strcmp(cmd, "z") == 0)
      {
          char       *pattern = psql_scan_slash_option(scan_state,
                                                       OT_NORMAL, NULL, true);
--- 2633,2653 ----
          success = do_pset("expanded", opt, &pset.popt, pset.quiet);
          free(opt);
      }
+     else
+         ignore_slash_options(scan_state);

!     return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
! }
!
! /*
!  * \z -- list table privileges (equivalent to \dp)
!  */
! static backslashResult
! exec_command_z(PsqlScanState scan_state, bool active_branch)
! {
!     bool        success = true;
!
!     if (active_branch)
      {
          char       *pattern = psql_scan_slash_option(scan_state,
                                                       OT_NORMAL, NULL, true);
*************** exec_command(const char *cmd,
*** 1709,1717 ****
          if (pattern)
              free(pattern);
      }

!     /* \! -- shell escape */
!     else if (strcmp(cmd, "!") == 0)
      {
          char       *opt = psql_scan_slash_option(scan_state,
                                                   OT_WHOLE_LINE, NULL, false);
--- 2656,2676 ----
          if (pattern)
              free(pattern);
      }
+     else
+         ignore_slash_options(scan_state);

!     return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
! }
!
! /*
!  * \! -- execute shell command
!  */
! static backslashResult
! exec_command_shell_escape(PsqlScanState scan_state, bool active_branch)
! {
!     bool        success = true;
!
!     if (active_branch)
      {
          char       *opt = psql_scan_slash_option(scan_state,
                                                   OT_WHOLE_LINE, NULL, false);
*************** exec_command(const char *cmd,
*** 1719,1727 ****
          success = do_shell(opt);
          free(opt);
      }

!     /* \? -- slash command help */
!     else if (strcmp(cmd, "?") == 0)
      {
          char       *opt0 = psql_scan_slash_option(scan_state,
                                                    OT_NORMAL, NULL, false);
--- 2678,2696 ----
          success = do_shell(opt);
          free(opt);
      }
+     else
+         ignore_slash_whole_line(scan_state);

!     return success ? PSQL_CMD_SKIP_LINE : PSQL_CMD_ERROR;
! }
!
! /*
!  * \? -- print help about backslash commands
!  */
! static backslashResult
! exec_command_slash_command_help(PsqlScanState scan_state, bool active_branch)
! {
!     if (active_branch)
      {
          char       *opt0 = psql_scan_slash_option(scan_state,
                                                    OT_NORMAL, NULL, false);
*************** exec_command(const char *cmd,
*** 1734,1767 ****
              helpVariables(pset.popt.topt.pager);
          else
              slashUsage(pset.popt.topt.pager);
      }

! #if 0

      /*
!      * These commands don't do anything. I just use them to test the parser.
       */
!     else if (strcmp(cmd, "void") == 0 || strcmp(cmd, "#") == 0)
!     {
!         int            i = 0;
!         char       *value;

!         while ((value = psql_scan_slash_option(scan_state,
!                                                OT_NORMAL, NULL, true)))
!         {
!             psql_error("+ opt(%d) = |%s|\n", i++, value);
!             free(value);
!         }
      }
- #endif

!     else
!         status = PSQL_CMD_UNKNOWN;

!     if (!success)
!         status = PSQL_CMD_ERROR;

!     return status;
  }

  /*
--- 2703,2933 ----
              helpVariables(pset.popt.topt.pager);
          else
              slashUsage(pset.popt.topt.pager);
+
+         if (opt0)
+             free(opt0);
      }
+     else
+         ignore_slash_options(scan_state);
+
+     return PSQL_CMD_SKIP_LINE;
+ }

!
! /*
!  * Read and interpret an argument to the \connect slash command.
!  */
! static char *
! read_connect_arg(PsqlScanState scan_state)
! {
!     char       *result;
!     char        quote;

      /*
!      * Ideally we should treat the arguments as SQL identifiers.  But for
!      * backwards compatibility with 7.2 and older pg_dump files, we have to
!      * take unquoted arguments verbatim (don't downcase them). For now,
!      * double-quoted arguments may be stripped of double quotes (as if SQL
!      * identifiers).  By 7.4 or so, pg_dump files can be expected to
!      * double-quote all mixed-case \connect arguments, and then we can get rid
!      * of OT_SQLIDHACK.
       */
!     result = psql_scan_slash_option(scan_state, OT_SQLIDHACK, "e, true);

!     if (!result)
!         return NULL;
!
!     if (quote)
!         return result;
!
!     if (*result == '\0' || strcmp(result, "-") == 0)
!         return NULL;
!
!     return result;
! }
!
! /*
!  * Read a boolean expression, return it as a PQExpBuffer string.
!  *
!  * Note: anything more or less than one token will certainly fail to be
!  * parsed by ParseVariableBool, so we don't worry about complaining here.
!  * This routine's return data structure will need to be rethought anyway
!  * to support likely future extensions such as "\if defined VARNAME".
!  */
! static PQExpBuffer
! gather_boolean_expression(PsqlScanState scan_state)
! {
!     PQExpBuffer exp_buf = createPQExpBuffer();
!     int            num_options = 0;
!     char       *value;
!
!     /* collect all arguments for the conditional command into exp_buf */
!     while ((value = psql_scan_slash_option(scan_state,
!                                            OT_NORMAL, NULL, false)) != NULL)
!     {
!         /* add spaces between tokens */
!         if (num_options > 0)
!             appendPQExpBufferChar(exp_buf, ' ');
!         appendPQExpBufferStr(exp_buf, value);
!         num_options++;
!         free(value);
      }

!     return exp_buf;
! }

! /*
!  * Read a boolean expression, return true if the expression
!  * was a valid boolean expression that evaluated to true.
!  * Otherwise return false.
!  *
!  * Note: conditional stack's top state must be active, else lexer will
!  * fail to expand variables and backticks.
!  */
! static bool
! is_true_boolean_expression(PsqlScanState scan_state, const char *name)
! {
!     PQExpBuffer buf = gather_boolean_expression(scan_state);
!     bool        value = false;
!     bool        success = ParseVariableBool(buf->data, name, &value);

!     destroyPQExpBuffer(buf);
!     return success && value;
! }
!
! /*
!  * Read a boolean expression, but do nothing with it.
!  *
!  * Note: conditional stack's top state must be INACTIVE, else lexer will
!  * expand variables and backticks, which we do not want here.
!  */
! static void
! ignore_boolean_expression(PsqlScanState scan_state)
! {
!     PQExpBuffer buf = gather_boolean_expression(scan_state);
!
!     destroyPQExpBuffer(buf);
! }
!
! /*
!  * Read and discard "normal" slash command options.
!  *
!  * This should be used for inactive-branch processing of any slash command
!  * that eats one or more OT_NORMAL, OT_SQLID, or OT_SQLIDHACK parameters.
!  * We don't need to worry about exactly how many it would eat, since the
!  * cleanup logic in HandleSlashCmds would silently discard any extras anyway.
!  */
! static void
! ignore_slash_options(PsqlScanState scan_state)
! {
!     char       *arg;
!
!     while ((arg = psql_scan_slash_option(scan_state,
!                                          OT_NORMAL, NULL, false)) != NULL)
!         free(arg);
! }
!
! /*
!  * Read and discard FILEPIPE slash command argument.
!  *
!  * This *MUST* be used for inactive-branch processing of any slash command
!  * that takes an OT_FILEPIPE option.  Otherwise we might consume a different
!  * amount of option text in active and inactive cases.
!  */
! static void
! ignore_slash_filepipe(PsqlScanState scan_state)
! {
!     char       *arg = psql_scan_slash_option(scan_state,
!                                              OT_FILEPIPE, NULL, false);
!
!     if (arg)
!         free(arg);
! }
!
! /*
!  * Read and discard whole-line slash command argument.
!  *
!  * This *MUST* be used for inactive-branch processing of any slash command
!  * that takes an OT_WHOLE_LINE option.  Otherwise we might consume a different
!  * amount of option text in active and inactive cases.
!  */
! static void
! ignore_slash_whole_line(PsqlScanState scan_state)
! {
!     char       *arg = psql_scan_slash_option(scan_state,
!                                              OT_WHOLE_LINE, NULL, false);
!
!     if (arg)
!         free(arg);
! }
!
! /*
!  * Return true if the command given is a branching command.
!  */
! static bool
! is_branching_command(const char *cmd)
! {
!     return (strcmp(cmd, "if") == 0 ||
!             strcmp(cmd, "elif") == 0 ||
!             strcmp(cmd, "else") == 0 ||
!             strcmp(cmd, "endif") == 0);
! }
!
! /*
!  * Prepare to possibly restore query buffer to its current state
!  * (cf. discard_query_text).
!  *
!  * We need to remember the length of the query buffer, and the lexer's
!  * notion of the parenthesis nesting depth.
!  */
! static void
! save_query_text_state(PsqlScanState scan_state, ConditionalStack cstack,
!                       PQExpBuffer query_buf)
! {
!     if (query_buf)
!         conditional_stack_set_query_len(cstack, query_buf->len);
!     conditional_stack_set_paren_depth(cstack,
!                                       psql_scan_get_paren_depth(scan_state));
! }
!
! /*
!  * Discard any query text absorbed during an inactive conditional branch.
!  *
!  * We must discard data that was appended to query_buf during an inactive
!  * \if branch.  We don't have to do anything there if there's no query_buf.
!  *
!  * Also, reset the lexer state to the same paren depth there was before.
!  * (The rest of its state doesn't need attention, since we could not be
!  * inside a comment or literal or partial token.)
!  */
! static void
! discard_query_text(PsqlScanState scan_state, ConditionalStack cstack,
!                    PQExpBuffer query_buf)
! {
!     if (query_buf)
!     {
!         int            new_len = conditional_stack_get_query_len(cstack);
!
!         Assert(new_len >= 0 && new_len <= query_buf->len);
!         query_buf->len = new_len;
!         query_buf->data[new_len] = '\0';
!     }
!     psql_scan_set_paren_depth(scan_state,
!                               conditional_stack_get_paren_depth(cstack));
! }
!
! /*
!  * If query_buf is empty, copy previous_buf into it.
!  *
!  * This is used by various slash commands for which re-execution of a
!  * previous query is a common usage.  For convenience, we allow the
!  * case of query_buf == NULL (and do nothing).
!  */
! static void
! copy_previous_query(PQExpBuffer query_buf, PQExpBuffer previous_buf)
! {
!     if (query_buf && query_buf->len == 0)
!         appendPQExpBufferStr(query_buf, previous_buf->data);
  }

  /*
diff --git a/src/bin/psql/command.h b/src/bin/psql/command.h
index d0c3264..e8ea847 100644
*** a/src/bin/psql/command.h
--- b/src/bin/psql/command.h
***************
*** 10,15 ****
--- 10,16 ----

  #include "fe_utils/print.h"
  #include "fe_utils/psqlscan.h"
+ #include "conditional.h"


  typedef enum _backslashResult
*************** typedef enum _backslashResult
*** 25,31 ****


  extern backslashResult HandleSlashCmds(PsqlScanState scan_state,
!                 PQExpBuffer query_buf);

  extern int    process_file(char *filename, bool use_relative_path);

--- 26,34 ----


  extern backslashResult HandleSlashCmds(PsqlScanState scan_state,
!                 ConditionalStack cstack,
!                 PQExpBuffer query_buf,
!                 PQExpBuffer previous_buf);

  extern int    process_file(char *filename, bool use_relative_path);

diff --git a/src/bin/psql/common.c b/src/bin/psql/common.c
index e9d4fe6..b06ae97 100644
*** a/src/bin/psql/common.c
--- b/src/bin/psql/common.c
*************** setQFout(const char *fname)
*** 121,127 ****
   * (Failure in escaping should lead to returning NULL.)
   *
   * "passthrough" is the pointer previously given to psql_scan_set_passthrough.
!  * psql currently doesn't use this.
   */
  char *
  psql_get_variable(const char *varname, bool escape, bool as_ident,
--- 121,128 ----
   * (Failure in escaping should lead to returning NULL.)
   *
   * "passthrough" is the pointer previously given to psql_scan_set_passthrough.
!  * In psql, passthrough points to a ConditionalStack, which we check to
!  * determine whether variable expansion is allowed.
   */
  char *
  psql_get_variable(const char *varname, bool escape, bool as_ident,
*************** psql_get_variable(const char *varname, b
*** 130,135 ****
--- 131,140 ----
      char       *result;
      const char *value;

+     /* In an inactive \if branch, suppress all variable substitutions */
+     if (passthrough && !conditional_active((ConditionalStack) passthrough))
+         return NULL;
+
      value = GetVariable(pset.vars, varname);
      if (!value)
          return NULL;
diff --git a/src/bin/psql/conditional.c b/src/bin/psql/conditional.c
index ...63977ce .
*** a/src/bin/psql/conditional.c
--- b/src/bin/psql/conditional.c
***************
*** 0 ****
--- 1,153 ----
+ /*
+  * psql - the PostgreSQL interactive terminal
+  *
+  * Copyright (c) 2000-2017, PostgreSQL Global Development Group
+  *
+  * src/bin/psql/conditional.c
+  */
+ #include "postgres_fe.h"
+
+ #include "conditional.h"
+
+ /*
+  * create stack
+  */
+ ConditionalStack
+ conditional_stack_create(void)
+ {
+     ConditionalStack cstack = pg_malloc(sizeof(ConditionalStackData));
+
+     cstack->head = NULL;
+     return cstack;
+ }
+
+ /*
+  * destroy stack
+  */
+ void
+ conditional_stack_destroy(ConditionalStack cstack)
+ {
+     while (conditional_stack_pop(cstack))
+         continue;
+     free(cstack);
+ }
+
+ /*
+  * Create a new conditional branch.
+  */
+ void
+ conditional_stack_push(ConditionalStack cstack, ifState new_state)
+ {
+     IfStackElem *p = (IfStackElem *) pg_malloc(sizeof(IfStackElem));
+
+     p->if_state = new_state;
+     p->query_len = -1;
+     p->paren_depth = -1;
+     p->next = cstack->head;
+     cstack->head = p;
+ }
+
+ /*
+  * Destroy the topmost conditional branch.
+  * Returns false if there was no branch to end.
+  */
+ bool
+ conditional_stack_pop(ConditionalStack cstack)
+ {
+     IfStackElem *p = cstack->head;
+
+     if (!p)
+         return false;
+     cstack->head = cstack->head->next;
+     free(p);
+     return true;
+ }
+
+ /*
+  * Fetch the current state of the top of the stack.
+  */
+ ifState
+ conditional_stack_peek(ConditionalStack cstack)
+ {
+     if (conditional_stack_empty(cstack))
+         return IFSTATE_NONE;
+     return cstack->head->if_state;
+ }
+
+ /*
+  * Change the state of the topmost branch.
+  * Returns false if there was no branch state to set.
+  */
+ bool
+ conditional_stack_poke(ConditionalStack cstack, ifState new_state)
+ {
+     if (conditional_stack_empty(cstack))
+         return false;
+     cstack->head->if_state = new_state;
+     return true;
+ }
+
+ /*
+  * True if there are no active \if-blocks.
+  */
+ bool
+ conditional_stack_empty(ConditionalStack cstack)
+ {
+     return cstack->head == NULL;
+ }
+
+ /*
+  * True if we should execute commands normally; that is, the current
+  * conditional branch is active, or there is no open \if block.
+  */
+ bool
+ conditional_active(ConditionalStack cstack)
+ {
+     ifState        s = conditional_stack_peek(cstack);
+
+     return s == IFSTATE_NONE || s == IFSTATE_TRUE || s == IFSTATE_ELSE_TRUE;
+ }
+
+ /*
+  * Save current query buffer length in topmost stack entry.
+  */
+ void
+ conditional_stack_set_query_len(ConditionalStack cstack, int len)
+ {
+     Assert(!conditional_stack_empty(cstack));
+     cstack->head->query_len = len;
+ }
+
+ /*
+  * Fetch last-recorded query buffer length from topmost stack entry.
+  * Will return -1 if no stack or it was never saved.
+  */
+ int
+ conditional_stack_get_query_len(ConditionalStack cstack)
+ {
+     if (conditional_stack_empty(cstack))
+         return -1;
+     return cstack->head->query_len;
+ }
+
+ /*
+  * Save current parenthesis nesting depth in topmost stack entry.
+  */
+ void
+ conditional_stack_set_paren_depth(ConditionalStack cstack, int depth)
+ {
+     Assert(!conditional_stack_empty(cstack));
+     cstack->head->paren_depth = depth;
+ }
+
+ /*
+  * Fetch last-recorded parenthesis nesting depth from topmost stack entry.
+  * Will return -1 if no stack or it was never saved.
+  */
+ int
+ conditional_stack_get_paren_depth(ConditionalStack cstack)
+ {
+     if (conditional_stack_empty(cstack))
+         return -1;
+     return cstack->head->paren_depth;
+ }
diff --git a/src/bin/psql/conditional.h b/src/bin/psql/conditional.h
index ...90e4d93 .
*** a/src/bin/psql/conditional.h
--- b/src/bin/psql/conditional.h
***************
*** 0 ****
--- 1,83 ----
+ /*
+  * psql - the PostgreSQL interactive terminal
+  *
+  * Copyright (c) 2000-2017, PostgreSQL Global Development Group
+  *
+  * src/bin/psql/conditional.h
+  */
+ #ifndef CONDITIONAL_H
+ #define CONDITIONAL_H
+
+ /*
+  * Possible states of a single level of \if block.
+  */
+ typedef enum ifState
+ {
+     IFSTATE_NONE = 0,            /* not currently in an \if block */
+     IFSTATE_TRUE,                /* currently in an \if or \elif that is true
+                                  * and all parent branches (if any) are true */
+     IFSTATE_FALSE,                /* currently in an \if or \elif that is false
+                                  * but no true branch has yet been seen, and
+                                  * all parent branches (if any) are true */
+     IFSTATE_IGNORED,            /* currently in an \elif that follows a true
+                                  * branch, or the whole \if is a child of a
+                                  * false parent branch */
+     IFSTATE_ELSE_TRUE,            /* currently in an \else that is true and all
+                                  * parent branches (if any) are true */
+     IFSTATE_ELSE_FALSE            /* currently in an \else that is false or
+                                  * ignored */
+ } ifState;
+
+ /*
+  * The state of nested \ifs is stored in a stack.
+  *
+  * query_len is used to determine what accumulated text to throw away at the
+  * end of an inactive branch.  (We could, perhaps, teach the lexer to not add
+  * stuff to the query buffer in the first place when inside an inactive branch;
+  * but that would be very invasive.)  We also need to save and restore the
+  * lexer's parenthesis nesting depth when throwing away text.  (We don't need
+  * to save and restore any of its other state, such as comment nesting depth,
+  * because a backslash command could never appear inside a comment or SQL
+  * literal.)
+  */
+ typedef struct IfStackElem
+ {
+     ifState        if_state;        /* current state, see enum above */
+     int            query_len;        /* length of query_buf at last branch start */
+     int            paren_depth;    /* parenthesis depth at last branch start */
+     struct IfStackElem *next;    /* next surrounding \if, if any */
+ } IfStackElem;
+
+ typedef struct ConditionalStackData
+ {
+     IfStackElem *head;
+ } ConditionalStackData;
+
+ typedef struct ConditionalStackData *ConditionalStack;
+
+
+ extern ConditionalStack conditional_stack_create(void);
+
+ extern void conditional_stack_destroy(ConditionalStack cstack);
+
+ extern void conditional_stack_push(ConditionalStack cstack, ifState new_state);
+
+ extern bool conditional_stack_pop(ConditionalStack cstack);
+
+ extern ifState conditional_stack_peek(ConditionalStack cstack);
+
+ extern bool conditional_stack_poke(ConditionalStack cstack, ifState new_state);
+
+ extern bool conditional_stack_empty(ConditionalStack cstack);
+
+ extern bool conditional_active(ConditionalStack cstack);
+
+ extern void conditional_stack_set_query_len(ConditionalStack cstack, int len);
+
+ extern int    conditional_stack_get_query_len(ConditionalStack cstack);
+
+ extern void conditional_stack_set_paren_depth(ConditionalStack cstack, int depth);
+
+ extern int    conditional_stack_get_paren_depth(ConditionalStack cstack);
+
+ #endif   /* CONDITIONAL_H */
diff --git a/src/bin/psql/copy.c b/src/bin/psql/copy.c
index 481031a..2005b9a 100644
*** a/src/bin/psql/copy.c
--- b/src/bin/psql/copy.c
*************** handleCopyIn(PGconn *conn, FILE *copystr
*** 552,558 ****
          /* interactive input probably silly, but give one prompt anyway */
          if (showprompt)
          {
!             const char *prompt = get_prompt(PROMPT_COPY);

              fputs(prompt, stdout);
              fflush(stdout);
--- 552,558 ----
          /* interactive input probably silly, but give one prompt anyway */
          if (showprompt)
          {
!             const char *prompt = get_prompt(PROMPT_COPY, NULL);

              fputs(prompt, stdout);
              fflush(stdout);
*************** handleCopyIn(PGconn *conn, FILE *copystr
*** 590,596 ****

              if (showprompt)
              {
!                 const char *prompt = get_prompt(PROMPT_COPY);

                  fputs(prompt, stdout);
                  fflush(stdout);
--- 590,596 ----

              if (showprompt)
              {
!                 const char *prompt = get_prompt(PROMPT_COPY, NULL);

                  fputs(prompt, stdout);
                  fflush(stdout);
diff --git a/src/bin/psql/help.c b/src/bin/psql/help.c
index ba14df0..ac43522 100644
*** a/src/bin/psql/help.c
--- b/src/bin/psql/help.c
*************** slashUsage(unsigned short int pager)
*** 167,173 ****
       * Use "psql --help=commands | wc" to count correctly.  It's okay to count
       * the USE_READLINE line even in builds without that.
       */
!     output = PageOutput(113, pager ? &(pset.popt.topt) : NULL);

      fprintf(output, _("General\n"));
      fprintf(output, _("  \\copyright             show PostgreSQL usage and distribution terms\n"));
--- 167,173 ----
       * Use "psql --help=commands | wc" to count correctly.  It's okay to count
       * the USE_READLINE line even in builds without that.
       */
!     output = PageOutput(122, pager ? &(pset.popt.topt) : NULL);

      fprintf(output, _("General\n"));
      fprintf(output, _("  \\copyright             show PostgreSQL usage and distribution terms\n"));
*************** slashUsage(unsigned short int pager)
*** 210,215 ****
--- 210,222 ----
      fprintf(output, _("  \\qecho [STRING]        write string to query output stream (see \\o)\n"));
      fprintf(output, "\n");

+     fprintf(output, _("Conditional\n"));
+     fprintf(output, _("  \\if EXPR               begin conditional block\n"));
+     fprintf(output, _("  \\elif EXPR             alternative within current conditional block\n"));
+     fprintf(output, _("  \\else                  final alternative within current conditional block\n"));
+     fprintf(output, _("  \\endif                 end conditional block\n"));
+     fprintf(output, "\n");
+
      fprintf(output, _("Informational\n"));
      fprintf(output, _("  (options: S = show system objects, + = additional detail)\n"));
      fprintf(output, _("  \\d[S+]                 list tables, views, and sequences\n"));
diff --git a/src/bin/psql/mainloop.c b/src/bin/psql/mainloop.c
index 6e358e2..2bc2f43 100644
*** a/src/bin/psql/mainloop.c
--- b/src/bin/psql/mainloop.c
*************** int
*** 35,40 ****
--- 35,41 ----
  MainLoop(FILE *source)
  {
      PsqlScanState scan_state;    /* lexer working state */
+     ConditionalStack cond_stack;    /* \if status stack */
      volatile PQExpBuffer query_buf;        /* buffer for query being accumulated */
      volatile PQExpBuffer previous_buf;    /* if there isn't anything in the new
                                           * buffer yet, use this one for \e,
*************** MainLoop(FILE *source)
*** 50,65 ****
      volatile promptStatus_t prompt_status = PROMPT_READY;
      volatile int count_eof = 0;
      volatile bool die_on_error = false;
-
-     /* Save the prior command source */
      FILE       *prev_cmd_source;
      bool        prev_cmd_interactive;
      uint64        prev_lineno;

!     /* Save old settings */
      prev_cmd_source = pset.cur_cmd_source;
      prev_cmd_interactive = pset.cur_cmd_interactive;
      prev_lineno = pset.lineno;

      /* Establish new source */
      pset.cur_cmd_source = source;
--- 51,65 ----
      volatile promptStatus_t prompt_status = PROMPT_READY;
      volatile int count_eof = 0;
      volatile bool die_on_error = false;
      FILE       *prev_cmd_source;
      bool        prev_cmd_interactive;
      uint64        prev_lineno;

!     /* Save the prior command source */
      prev_cmd_source = pset.cur_cmd_source;
      prev_cmd_interactive = pset.cur_cmd_interactive;
      prev_lineno = pset.lineno;
+     /* pset.stmt_lineno does not need to be saved and restored */

      /* Establish new source */
      pset.cur_cmd_source = source;
*************** MainLoop(FILE *source)
*** 69,74 ****
--- 69,76 ----

      /* Create working state */
      scan_state = psql_scan_create(&psqlscan_callbacks);
+     cond_stack = conditional_stack_create();
+     psql_scan_set_passthrough(scan_state, (void *) cond_stack);

      query_buf = createPQExpBuffer();
      previous_buf = createPQExpBuffer();
*************** MainLoop(FILE *source)
*** 122,128 ****
--- 124,142 ----
              cancel_pressed = false;

              if (pset.cur_cmd_interactive)
+             {
                  putc('\n', stdout);
+
+                 /*
+                  * if interactive user is in an \if block, then Ctrl-C will
+                  * exit from the innermost \if.
+                  */
+                 if (!conditional_stack_empty(cond_stack))
+                 {
+                     psql_error("\\if: escaped\n");
+                     conditional_stack_pop(cond_stack);
+                 }
+             }
              else
              {
                  successResult = EXIT_USER;
*************** MainLoop(FILE *source)
*** 140,146 ****
              /* May need to reset prompt, eg after \r command */
              if (query_buf->len == 0)
                  prompt_status = PROMPT_READY;
!             line = gets_interactive(get_prompt(prompt_status), query_buf);
          }
          else
          {
--- 154,161 ----
              /* May need to reset prompt, eg after \r command */
              if (query_buf->len == 0)
                  prompt_status = PROMPT_READY;
!             line = gets_interactive(get_prompt(prompt_status, cond_stack),
!                                     query_buf);
          }
          else
          {
*************** MainLoop(FILE *source)
*** 286,293 ****
                  (scan_result == PSCAN_EOL && pset.singleline))
              {
                  /*
!                  * Save query in history.  We use history_buf to accumulate
!                  * multi-line queries into a single history entry.
                   */
                  if (pset.cur_cmd_interactive && !line_saved_in_history)
                  {
--- 301,310 ----
                  (scan_result == PSCAN_EOL && pset.singleline))
              {
                  /*
!                  * Save line in history.  We use history_buf to accumulate
!                  * multi-line queries into a single history entry.  Note that
!                  * history accumulation works on input lines, so it doesn't
!                  * matter whether the query will be ignored due to \if.
                   */
                  if (pset.cur_cmd_interactive && !line_saved_in_history)
                  {
*************** MainLoop(FILE *source)
*** 296,317 ****
                      line_saved_in_history = true;
                  }

!                 /* execute query */
!                 success = SendQuery(query_buf->data);
!                 slashCmdStatus = success ? PSQL_CMD_SEND : PSQL_CMD_ERROR;
!                 pset.stmt_lineno = 1;
!
!                 /* transfer query to previous_buf by pointer-swapping */
                  {
!                     PQExpBuffer swap_buf = previous_buf;

!                     previous_buf = query_buf;
!                     query_buf = swap_buf;
!                 }
!                 resetPQExpBuffer(query_buf);

!                 added_nl_pos = -1;
!                 /* we need not do psql_scan_reset() here */
              }
              else if (scan_result == PSCAN_BACKSLASH)
              {
--- 313,348 ----
                      line_saved_in_history = true;
                  }

!                 /* execute query unless we're in an inactive \if branch */
!                 if (conditional_active(cond_stack))
                  {
!                     success = SendQuery(query_buf->data);
!                     slashCmdStatus = success ? PSQL_CMD_SEND : PSQL_CMD_ERROR;
!                     pset.stmt_lineno = 1;

!                     /* transfer query to previous_buf by pointer-swapping */
!                     {
!                         PQExpBuffer swap_buf = previous_buf;

!                         previous_buf = query_buf;
!                         query_buf = swap_buf;
!                     }
!                     resetPQExpBuffer(query_buf);
!
!                     added_nl_pos = -1;
!                     /* we need not do psql_scan_reset() here */
!                 }
!                 else
!                 {
!                     /* if interactive, warn about non-executed query */
!                     if (pset.cur_cmd_interactive)
!                         psql_error("query ignored; use \\endif or Ctrl-C to exit current \\if block\n");
!                     /* fake an OK result for purposes of loop checks */
!                     success = true;
!                     slashCmdStatus = PSQL_CMD_SEND;
!                     pset.stmt_lineno = 1;
!                     /* note that query_buf doesn't change state */
!                 }
              }
              else if (scan_result == PSCAN_BACKSLASH)
              {
*************** MainLoop(FILE *source)
*** 343,363 ****

                  /* execute backslash command */
                  slashCmdStatus = HandleSlashCmds(scan_state,
!                                                  query_buf->len > 0 ?
!                                                  query_buf : previous_buf);

                  success = slashCmdStatus != PSQL_CMD_ERROR;
-                 pset.stmt_lineno = 1;

!                 if ((slashCmdStatus == PSQL_CMD_SEND || slashCmdStatus == PSQL_CMD_NEWEDIT) &&
!                     query_buf->len == 0)
!                 {
!                     /* copy previous buffer to current for handling */
!                     appendPQExpBufferStr(query_buf, previous_buf->data);
!                 }

                  if (slashCmdStatus == PSQL_CMD_SEND)
                  {
                      success = SendQuery(query_buf->data);

                      /* transfer query to previous_buf by pointer-swapping */
--- 374,397 ----

                  /* execute backslash command */
                  slashCmdStatus = HandleSlashCmds(scan_state,
!                                                  cond_stack,
!                                                  query_buf,
!                                                  previous_buf);

                  success = slashCmdStatus != PSQL_CMD_ERROR;

!                 /*
!                  * Resetting stmt_lineno after a backslash command isn't
!                  * always appropriate, but it's what we've done historically
!                  * and there have been few complaints.
!                  */
!                 pset.stmt_lineno = 1;

                  if (slashCmdStatus == PSQL_CMD_SEND)
                  {
+                     /* should not see this in inactive branch */
+                     Assert(conditional_active(cond_stack));
+
                      success = SendQuery(query_buf->data);

                      /* transfer query to previous_buf by pointer-swapping */
*************** MainLoop(FILE *source)
*** 374,379 ****
--- 408,415 ----
                  }
                  else if (slashCmdStatus == PSQL_CMD_NEWEDIT)
                  {
+                     /* should not see this in inactive branch */
+                     Assert(conditional_active(cond_stack));
                      /* rescan query_buf as new input */
                      psql_scan_finish(scan_state);
                      free(line);
*************** MainLoop(FILE *source)
*** 429,436 ****
          if (pset.cur_cmd_interactive)
              pg_send_history(history_buf);

!         /* execute query */
!         success = SendQuery(query_buf->data);

          if (!success && die_on_error)
              successResult = EXIT_USER;
--- 465,481 ----
          if (pset.cur_cmd_interactive)
              pg_send_history(history_buf);

!         /* execute query unless we're in an inactive \if branch */
!         if (conditional_active(cond_stack))
!         {
!             success = SendQuery(query_buf->data);
!         }
!         else
!         {
!             if (pset.cur_cmd_interactive)
!                 psql_error("query ignored; use \\endif or Ctrl-C to exit current \\if block\n");
!             success = true;
!         }

          if (!success && die_on_error)
              successResult = EXIT_USER;
*************** MainLoop(FILE *source)
*** 439,444 ****
--- 484,502 ----
      }

      /*
+      * Check for unbalanced \if-\endifs unless user explicitly quit, or the
+      * script is erroring out
+      */
+     if (slashCmdStatus != PSQL_CMD_TERMINATE &&
+         successResult != EXIT_USER &&
+         !conditional_stack_empty(cond_stack))
+     {
+         psql_error("reached EOF without finding closing \\endif(s)\n");
+         if (die_on_error && !pset.cur_cmd_interactive)
+             successResult = EXIT_USER;
+     }
+
+     /*
       * Let's just make real sure the SIGINT handler won't try to use
       * sigint_interrupt_jmp after we exit this routine.  If there is an outer
       * MainLoop instance, it will reset sigint_interrupt_jmp to point to
*************** MainLoop(FILE *source)
*** 452,457 ****
--- 510,516 ----
      destroyPQExpBuffer(history_buf);

      psql_scan_destroy(scan_state);
+     conditional_stack_destroy(cond_stack);

      pset.cur_cmd_source = prev_cmd_source;
      pset.cur_cmd_interactive = prev_cmd_interactive;
diff --git a/src/bin/psql/prompt.c b/src/bin/psql/prompt.c
index f7930c4..e502ff3 100644
*** a/src/bin/psql/prompt.c
--- b/src/bin/psql/prompt.c
***************
*** 66,72 ****
   */

  char *
! get_prompt(promptStatus_t status)
  {
  #define MAX_PROMPT_SIZE 256
      static char destination[MAX_PROMPT_SIZE + 1];
--- 66,72 ----
   */

  char *
! get_prompt(promptStatus_t status, ConditionalStack cstack)
  {
  #define MAX_PROMPT_SIZE 256
      static char destination[MAX_PROMPT_SIZE + 1];
*************** get_prompt(promptStatus_t status)
*** 188,194 ****
                      switch (status)
                      {
                          case PROMPT_READY:
!                             if (!pset.db)
                                  buf[0] = '!';
                              else if (!pset.singleline)
                                  buf[0] = '=';
--- 188,196 ----
                      switch (status)
                      {
                          case PROMPT_READY:
!                             if (cstack != NULL && !conditional_active(cstack))
!                                 buf[0] = '@';
!                             else if (!pset.db)
                                  buf[0] = '!';
                              else if (!pset.singleline)
                                  buf[0] = '=';
diff --git a/src/bin/psql/prompt.h b/src/bin/psql/prompt.h
index 977e754..b3d2d98 100644
*** a/src/bin/psql/prompt.h
--- b/src/bin/psql/prompt.h
***************
*** 10,16 ****

  /* enum promptStatus_t is now defined by psqlscan.h */
  #include "fe_utils/psqlscan.h"

! char       *get_prompt(promptStatus_t status);

  #endif   /* PROMPT_H */
--- 10,17 ----

  /* enum promptStatus_t is now defined by psqlscan.h */
  #include "fe_utils/psqlscan.h"
+ #include "conditional.h"

! char       *get_prompt(promptStatus_t status, ConditionalStack cstack);

  #endif   /* PROMPT_H */
diff --git a/src/bin/psql/psqlscanslash.h b/src/bin/psql/psqlscanslash.h
index 266e93a..db76061 100644
*** a/src/bin/psql/psqlscanslash.h
--- b/src/bin/psql/psqlscanslash.h
*************** enum slash_option_type
*** 18,25 ****
      OT_SQLID,                    /* treat as SQL identifier */
      OT_SQLIDHACK,                /* SQL identifier, but don't downcase */
      OT_FILEPIPE,                /* it's a filename or pipe */
!     OT_WHOLE_LINE,                /* just snarf the rest of the line */
!     OT_NO_EVAL                    /* no expansion of backticks or variables */
  };


--- 18,24 ----
      OT_SQLID,                    /* treat as SQL identifier */
      OT_SQLIDHACK,                /* SQL identifier, but don't downcase */
      OT_FILEPIPE,                /* it's a filename or pipe */
!     OT_WHOLE_LINE                /* just snarf the rest of the line */
  };


*************** extern char *psql_scan_slash_option(Psql
*** 32,37 ****
--- 31,40 ----

  extern void psql_scan_slash_command_end(PsqlScanState state);

+ extern int    psql_scan_get_paren_depth(PsqlScanState state);
+
+ extern void psql_scan_set_paren_depth(PsqlScanState state, int depth);
+
  extern void dequote_downcase_identifier(char *str, bool downcase, int encoding);

  #endif   /* PSQLSCANSLASH_H */
diff --git a/src/bin/psql/psqlscanslash.l b/src/bin/psql/psqlscanslash.l
index ba4a08d..319afdc 100644
*** a/src/bin/psql/psqlscanslash.l
--- b/src/bin/psql/psqlscanslash.l
***************
*** 19,24 ****
--- 19,25 ----
  #include "postgres_fe.h"

  #include "psqlscanslash.h"
+ #include "conditional.h"

  #include "libpq-fe.h"
  }
*************** other            .
*** 230,237 ****

  :{variable_char}+    {
                      /* Possible psql variable substitution */
!                     if (option_type == OT_NO_EVAL ||
!                         cur_state->callbacks->get_variable == NULL)
                          ECHO;
                      else
                      {
--- 231,237 ----

  :{variable_char}+    {
                      /* Possible psql variable substitution */
!                     if (cur_state->callbacks->get_variable == NULL)
                          ECHO;
                      else
                      {
*************** other            .
*** 268,292 ****
                  }

  :'{variable_char}+'    {
!                     if (option_type == OT_NO_EVAL)
!                         ECHO;
!                     else
!                     {
!                         psqlscan_escape_variable(cur_state, yytext, yyleng, false);
!                         *option_quote = ':';
!                     }
                      unquoted_option_chars = 0;
                  }


  :\"{variable_char}+\"    {
!                     if (option_type == OT_NO_EVAL)
!                         ECHO;
!                     else
!                     {
!                         psqlscan_escape_variable(cur_state, yytext, yyleng, true);
!                         *option_quote = ':';
!                     }
                      unquoted_option_chars = 0;
                  }

--- 268,282 ----
                  }

  :'{variable_char}+'    {
!                     psqlscan_escape_variable(cur_state, yytext, yyleng, false);
!                     *option_quote = ':';
                      unquoted_option_chars = 0;
                  }


  :\"{variable_char}+\"    {
!                     psqlscan_escape_variable(cur_state, yytext, yyleng, true);
!                     *option_quote = ':';
                      unquoted_option_chars = 0;
                  }

*************** other            .
*** 353,360 ****
       */

  "`"                {
!                     /* In NO_EVAL mode, don't evaluate the command */
!                     if (option_type != OT_NO_EVAL)
                          evaluate_backtick(cur_state);
                      BEGIN(xslasharg);
                  }
--- 343,351 ----
       */

  "`"                {
!                     /* In an inactive \if branch, don't evaluate the command */
!                     if (cur_state->cb_passthrough == NULL ||
!                         conditional_active((ConditionalStack) cur_state->cb_passthrough))
                          evaluate_backtick(cur_state);
                      BEGIN(xslasharg);
                  }
*************** psql_scan_slash_command_end(PsqlScanStat
*** 642,647 ****
--- 633,657 ----
  }

  /*
+  * Fetch current paren nesting depth
+  */
+ int
+ psql_scan_get_paren_depth(PsqlScanState state)
+ {
+     return state->paren_depth;
+ }
+
+ /*
+  * Set paren nesting depth
+  */
+ void
+ psql_scan_set_paren_depth(PsqlScanState state, int depth)
+ {
+     Assert(depth >= 0);
+     state->paren_depth = depth;
+ }
+
+ /*
   * De-quote and optionally downcase a SQL identifier.
   *
   * The string at *str is modified in-place; it can become shorter,
diff --git a/src/bin/psql/startup.c b/src/bin/psql/startup.c
index 694f0ef..8068a28 100644
*** a/src/bin/psql/startup.c
--- b/src/bin/psql/startup.c
*************** main(int argc, char *argv[])
*** 331,336 ****
--- 331,337 ----
              else if (cell->action == ACT_SINGLE_SLASH)
              {
                  PsqlScanState scan_state;
+                 ConditionalStack cond_stack;

                  if (pset.echo == PSQL_ECHO_ALL)
                      puts(cell->val);
*************** main(int argc, char *argv[])
*** 339,349 ****
                  psql_scan_setup(scan_state,
                                  cell->val, strlen(cell->val),
                                  pset.encoding, standard_strings());

!                 successResult = HandleSlashCmds(scan_state, NULL) != PSQL_CMD_ERROR
                      ? EXIT_SUCCESS : EXIT_FAILURE;

                  psql_scan_destroy(scan_state);
              }
              else if (cell->action == ACT_FILE)
              {
--- 340,356 ----
                  psql_scan_setup(scan_state,
                                  cell->val, strlen(cell->val),
                                  pset.encoding, standard_strings());
+                 cond_stack = conditional_stack_create();
+                 psql_scan_set_passthrough(scan_state, (void *) cond_stack);

!                 successResult = HandleSlashCmds(scan_state,
!                                                 cond_stack,
!                                                 NULL,
!                                                 NULL) != PSQL_CMD_ERROR
                      ? EXIT_SUCCESS : EXIT_FAILURE;

                  psql_scan_destroy(scan_state);
+                 conditional_stack_destroy(cond_stack);
              }
              else if (cell->action == ACT_FILE)
              {
diff --git a/src/test/regress/expected/psql.out b/src/test/regress/expected/psql.out
index eb7f197..50251c3 100644
*** a/src/test/regress/expected/psql.out
--- b/src/test/regress/expected/psql.out
*************** deallocate q;
*** 2735,2740 ****
--- 2735,2907 ----
  \pset format aligned
  \pset expanded off
  \pset border 1
+ -- tests for \if ... \endif
+ \if true
+   select 'okay';
+  ?column?
+ ----------
+  okay
+ (1 row)
+
+   select 'still okay';
+   ?column?
+ ------------
+  still okay
+ (1 row)
+
+ \else
+   not okay;
+   still not okay
+ \endif
+ -- at this point query buffer should still have last valid line
+ \g
+   ?column?
+ ------------
+  still okay
+ (1 row)
+
+ -- \if should work okay on part of a query
+ select
+   \if true
+     42
+   \else
+     (bogus
+   \endif
+   forty_two;
+  forty_two
+ -----------
+         42
+ (1 row)
+
+ select \if false \\ (bogus \else \\ 42 \endif \\ forty_two;
+  forty_two
+ -----------
+         42
+ (1 row)
+
+ -- test a large nested if using a variety of true-equivalents
+ \if true
+     \if 1
+         \if yes
+             \if on
+                 \echo 'all true'
+ all true
+             \else
+                 \echo 'should not print #1-1'
+             \endif
+         \else
+             \echo 'should not print #1-2'
+         \endif
+     \else
+         \echo 'should not print #1-3'
+     \endif
+ \else
+     \echo 'should not print #1-4'
+ \endif
+ -- test a variety of false-equivalents in an if/elif/else structure
+ \if false
+     \echo 'should not print #2-1'
+ \elif 0
+     \echo 'should not print #2-2'
+ \elif no
+     \echo 'should not print #2-3'
+ \elif off
+     \echo 'should not print #2-4'
+ \else
+     \echo 'all false'
+ all false
+ \endif
+ -- test simple true-then-else
+ \if true
+     \echo 'first thing true'
+ first thing true
+ \else
+     \echo 'should not print #3-1'
+ \endif
+ -- test simple false-true-else
+ \if false
+     \echo 'should not print #4-1'
+ \elif true
+     \echo 'second thing true'
+ second thing true
+ \else
+     \echo 'should not print #5-1'
+ \endif
+ -- invalid boolean expressions are false
+ \if invalid_boolean_expression
+ unrecognized value "invalid_boolean_expression" for "\if expression": boolean expected
+     \echo 'will not print #6-1'
+ \else
+     \echo 'will print anyway #6-2'
+ will print anyway #6-2
+ \endif
+ -- test un-matched endif
+ \endif
+ \endif: no matching \if
+ -- test un-matched else
+ \else
+ \else: no matching \if
+ -- test un-matched elif
+ \elif
+ \elif: no matching \if
+ -- test double-else error
+ \if true
+ \else
+ \else
+ \else: cannot occur after \else
+ \endif
+ -- test elif out-of-order
+ \if false
+ \else
+ \elif
+ \elif: cannot occur after \else
+ \endif
+ -- test if-endif matching in a false branch
+ \if false
+     \if false
+         \echo 'should not print #7-1'
+     \else
+         \echo 'should not print #7-2'
+     \endif
+     \echo 'should not print #7-3'
+ \else
+     \echo 'should print #7-4'
+ should print #7-4
+ \endif
+ -- show that vars and backticks are not expanded when ignoring extra args
+ \set foo bar
+ \echo :foo :'foo' :"foo"
+ bar 'bar' "bar"
+ \pset fieldsep | `nosuchcommand` :foo :'foo' :"foo"
+ \pset: extra argument "nosuchcommand" ignored
+ \pset: extra argument ":foo" ignored
+ \pset: extra argument ":'foo'" ignored
+ \pset: extra argument ":"foo"" ignored
+ -- show that vars and backticks are not expanded and commands are ignored
+ -- when in a false if-branch
+ \set try_to_quit '\\q'
+ \if false
+     :try_to_quit
+     \echo `nosuchcommand` :foo :'foo' :"foo"
+     \pset fieldsep | `nosuchcommand` :foo :'foo' :"foo"
+     \a \C arg1 \c arg1 arg2 arg3 arg4 \cd arg1 \conninfo
+     \copy arg1 arg2 arg3 arg4 arg5 arg6
+     \copyright \dt arg1 \e arg1 arg2
+     \ef whole_line
+     \ev whole_line
+     \echo arg1 arg2 arg3 arg4 arg5 \echo arg1 \encoding arg1 \errverbose
+     \g arg1 \gx arg1 \gexec \h \html \i arg1 \ir arg1 \l arg1 \lo arg1 arg2
+     \o arg1 \p \password arg1 \prompt arg1 arg2 \pset arg1 arg2 \q
+     \reset \s arg1 \set arg1 arg2 arg3 arg4 arg5 arg6 arg7 \setenv arg1 arg2
+     \sf whole_line
+     \sv whole_line
+     \t arg1 \T arg1 \timing arg1 \unset arg1 \w arg1 \watch arg1 \x arg1
+     -- \endif here is eaten as part of whole-line argument
+     \! whole_line \endif
+ \else
+     \echo 'should print #8-1'
+ should print #8-1
+ \endif
  -- SHOW_CONTEXT
  \set SHOW_CONTEXT never
  do $$
diff --git a/src/test/regress/sql/psql.sql b/src/test/regress/sql/psql.sql
index 8f8e17a..d9ab508 100644
*** a/src/test/regress/sql/psql.sql
--- b/src/test/regress/sql/psql.sql
*************** deallocate q;
*** 382,387 ****
--- 382,529 ----
  \pset expanded off
  \pset border 1

+ -- tests for \if ... \endif
+
+ \if true
+   select 'okay';
+   select 'still okay';
+ \else
+   not okay;
+   still not okay
+ \endif
+
+ -- at this point query buffer should still have last valid line
+ \g
+
+ -- \if should work okay on part of a query
+ select
+   \if true
+     42
+   \else
+     (bogus
+   \endif
+   forty_two;
+
+ select \if false \\ (bogus \else \\ 42 \endif \\ forty_two;
+
+ -- test a large nested if using a variety of true-equivalents
+ \if true
+     \if 1
+         \if yes
+             \if on
+                 \echo 'all true'
+             \else
+                 \echo 'should not print #1-1'
+             \endif
+         \else
+             \echo 'should not print #1-2'
+         \endif
+     \else
+         \echo 'should not print #1-3'
+     \endif
+ \else
+     \echo 'should not print #1-4'
+ \endif
+
+ -- test a variety of false-equivalents in an if/elif/else structure
+ \if false
+     \echo 'should not print #2-1'
+ \elif 0
+     \echo 'should not print #2-2'
+ \elif no
+     \echo 'should not print #2-3'
+ \elif off
+     \echo 'should not print #2-4'
+ \else
+     \echo 'all false'
+ \endif
+
+ -- test simple true-then-else
+ \if true
+     \echo 'first thing true'
+ \else
+     \echo 'should not print #3-1'
+ \endif
+
+ -- test simple false-true-else
+ \if false
+     \echo 'should not print #4-1'
+ \elif true
+     \echo 'second thing true'
+ \else
+     \echo 'should not print #5-1'
+ \endif
+
+ -- invalid boolean expressions are false
+ \if invalid_boolean_expression
+     \echo 'will not print #6-1'
+ \else
+     \echo 'will print anyway #6-2'
+ \endif
+
+ -- test un-matched endif
+ \endif
+
+ -- test un-matched else
+ \else
+
+ -- test un-matched elif
+ \elif
+
+ -- test double-else error
+ \if true
+ \else
+ \else
+ \endif
+
+ -- test elif out-of-order
+ \if false
+ \else
+ \elif
+ \endif
+
+ -- test if-endif matching in a false branch
+ \if false
+     \if false
+         \echo 'should not print #7-1'
+     \else
+         \echo 'should not print #7-2'
+     \endif
+     \echo 'should not print #7-3'
+ \else
+     \echo 'should print #7-4'
+ \endif
+
+ -- show that vars and backticks are not expanded when ignoring extra args
+ \set foo bar
+ \echo :foo :'foo' :"foo"
+ \pset fieldsep | `nosuchcommand` :foo :'foo' :"foo"
+
+ -- show that vars and backticks are not expanded and commands are ignored
+ -- when in a false if-branch
+ \set try_to_quit '\\q'
+ \if false
+     :try_to_quit
+     \echo `nosuchcommand` :foo :'foo' :"foo"
+     \pset fieldsep | `nosuchcommand` :foo :'foo' :"foo"
+     \a \C arg1 \c arg1 arg2 arg3 arg4 \cd arg1 \conninfo
+     \copy arg1 arg2 arg3 arg4 arg5 arg6
+     \copyright \dt arg1 \e arg1 arg2
+     \ef whole_line
+     \ev whole_line
+     \echo arg1 arg2 arg3 arg4 arg5 \echo arg1 \encoding arg1 \errverbose
+     \g arg1 \gx arg1 \gexec \h \html \i arg1 \ir arg1 \l arg1 \lo arg1 arg2
+     \o arg1 \p \password arg1 \prompt arg1 arg2 \pset arg1 arg2 \q
+     \reset \s arg1 \set arg1 arg2 arg3 arg4 arg5 arg6 arg7 \setenv arg1 arg2
+     \sf whole_line
+     \sv whole_line
+     \t arg1 \T arg1 \timing arg1 \unset arg1 \w arg1 \watch arg1 \x arg1
+     -- \endif here is eaten as part of whole-line argument
+     \! whole_line \endif
+ \else
+     \echo 'should print #8-1'
+ \endif
+
  -- SHOW_CONTEXT

  \set SHOW_CONTEXT never

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