Re: proposal: alternative psql commands quit and exit - Mailing list pgsql-hackers

On Thu, Jan 25, 2018 at 03:46:30PM -0500, Bruce Momjian wrote:
> On Mon, Jan 15, 2018 at 11:10:44AM -0500, Robert Haas wrote:
> > prompt_status does seem to be available in psql's MainLoop(), so I
> > think that could be done, but the problem is that I don't know exactly
> > what message would be useful to print when we're in a "in quotes"
> > state.  If I had a good message text for that state, I might just
> > choose to use it always rather than multiplying the number of
> > messages.
> > 
> > More broadly, I think what is needed here is less C-fu than
> > English-fu.  If we come up with something good, we can make it print
> > that thing.
> 
> I just read this thread and have some ideas.  First, the reason 'help'
> was added so easily is because it pointed users at getting more
> information, and it required to be the first command in the query
> buffer.
> 
> I realize we are now considering allowing 'help', 'quit', and 'exit' to
> appear alone on a line with whitespace before it, and remove the
> requirement that it be the first thing in the query buffer.
> 
> I think there are a few things to consider.
> 
> First, allowing whitespace to be before the keyword --- do we really
> think that typing <space>exit will more likely be typed by a user trying
> to exit than part of an SQL query?  I think requiring no space around
> the keyword would reduce the number of false hints.
> 
> Second, I am thinking we can check prompt_status and report "Use \q" if
> we are not in a quoted string, and suggest "Use Control-D then \q" (or
> "Use Control-C then \q" on Windows) and be done with it.  By printing
> the Control-D only when we are in a quoted strong, we minimize the
> number of times that we are wrong due to stty changes.

I used Robert's patch and modified it to match the ideas I had above.
Specifically no white space can be before 'help', 'exit' or 'quit' and
prompt_status is used to adjust the suggestion.  Here is the visible
behavior:

    test=> exit
    (exits)
    
    test=> SELECT
    test-> exit
-->    Use \q to quit.
    test-> \q

    test=> SELECT '
    test'> exit
-->    Use control-D to quit.
    test'> \q

    test=> SELECT "
    test"> exit
-->    Use control-D to quit.
    test"> \q
    
    test=> SELECT /*
    test*> exit
-->    Use control-D to quit.
    test*> \q

    test=> SELECT 'asbs' AS
    test-> exit
-->    Use \q to quit.
    test-> \q

    test=> SELECT 'asbs' AS
    test->     exit
    test-> ;
     exit
    ------
     asbs
    (1 row)

One open issue is the existing help display is inaccurate on Windows:

    Use \\? for help or press control-C to clear the input buffer.

Oh, it clears the input buffer alright, _and_ exits psql.  This patch
also removes the control-C mention on Windows.

-- 
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

+ As you are, so once was I.  As I am, so you will be. +
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