From 5f2d070d3cc47f7461d1474a5fe18e905243b31b Mon Sep 17 00:00:00 2001
From: jian he <jian.universality@gmail.com>
Date: Mon, 1 Jul 2024 14:26:09 +0800
Subject: [PATCH v1 1/1] hanlde types that have type modifier for json on
 error, on empty

---
 src/backend/parser/parse_expr.c | 83 ++++++++++++++++++++++++++-------
 1 file changed, 65 insertions(+), 18 deletions(-)

diff --git a/src/backend/parser/parse_expr.c b/src/backend/parser/parse_expr.c
index 560b3606..15cdea1c 100644
--- a/src/backend/parser/parse_expr.c
+++ b/src/backend/parser/parse_expr.c
@@ -3582,7 +3582,7 @@ coerceJsonFuncExpr(ParseState *pstate, Node *expr,
 	Node	   *res;
 	int			location;
 	Oid			exprtype = exprType(expr);
-	int32		baseTypmod = returning->typmod;
+	int32		baseTypmod = -1;
 
 	/* if output type is not specified or equals to function type, return */
 	if (!OidIsValid(returning->typid) || returning->typid == exprtype)
@@ -3615,8 +3615,10 @@ coerceJsonFuncExpr(ParseState *pstate, Node *expr,
 	 * For domains, consider the base type's typmod to decide whether to setup
 	 * an implicit or explicit cast.
 	 */
-	if (get_typtype(returning->typid) == TYPTYPE_DOMAIN)
+	if (returning->typmod < 0)
 		(void) getBaseTypeAndTypmod(returning->typid, &baseTypmod);
+	else
+		baseTypmod = returning->typmod;
 
 	/* try to coerce expression to the output type */
 	res = coerce_to_target_type(pstate, expr, exprtype,
@@ -3649,7 +3651,7 @@ makeJsonConstructorExpr(ParseState *pstate, JsonConstructorType type,
 	JsonConstructorExpr *jsctor = makeNode(JsonConstructorExpr);
 	Node	   *placeholder;
 	Node	   *coercion;
-	int32		baseTypmod = returning->typmod;
+	int32		baseTypmod = -1;
 
 	jsctor->args = args;
 	jsctor->func = fexpr;
@@ -3693,8 +3695,10 @@ makeJsonConstructorExpr(ParseState *pstate, JsonConstructorType type,
 	 * there are no implicit casts from json(b) to such types.  For domains,
 	 * the base type's typmod will be considered, so do so here too.
 	 */
-	if (get_typtype(returning->typid) == TYPTYPE_DOMAIN)
+	if (returning->typmod < 0)
 		(void) getBaseTypeAndTypmod(returning->typid, &baseTypmod);
+	else
+		baseTypmod = returning->typmod;
 	if (baseTypmod > 0)
 		placeholder = coerce_to_specific_type(pstate, placeholder, TEXTOID,
 											  "JSON_CONSTRUCTOR()");
@@ -4718,22 +4722,65 @@ transformJsonBehavior(ParseState *pstate, JsonBehavior *behavior,
 			coerce_at_runtime = true;
 		else
 		{
-			int32		baseTypmod = returning->typmod;
-
-			if (get_typtype(returning->typid) == TYPTYPE_DOMAIN)
+			int32		baseTypmod = -1;
+			char		typcategory;
+			bool		typispreferred;
+			get_type_category_preferred(returning->typid, &typcategory, &typispreferred);
+			if (returning->typmod < 0)
 				(void) getBaseTypeAndTypmod(returning->typid, &baseTypmod);
+			else
+				baseTypmod = returning->typmod;
 
-			if (baseTypmod > 0)
-				expr = coerce_to_specific_type(pstate, expr, TEXTOID,
-											   "JSON_FUNCTION()");
-			coerced_expr =
-				coerce_to_target_type(pstate, expr, exprType(expr),
-									  returning->typid, baseTypmod,
-									  baseTypmod > 0 ? COERCION_IMPLICIT :
-									  COERCION_EXPLICIT,
-									  baseTypmod > 0 ? COERCE_IMPLICIT_CAST :
-									  COERCE_EXPLICIT_CAST,
-									  exprLocation((Node *) behavior));
+			if (typcategory == TYPCATEGORY_STRING)
+			{
+				if (baseTypmod > 0)
+					expr = coerce_to_specific_type(pstate, expr, TEXTOID,
+												"JSON_FUNCTION()");
+				coerced_expr =
+					coerce_to_target_type(pstate, expr, exprType(expr),
+										returning->typid, baseTypmod,
+										baseTypmod > 0 ? COERCION_IMPLICIT :
+										COERCION_EXPLICIT,
+										baseTypmod > 0 ? COERCE_IMPLICIT_CAST :
+										COERCE_EXPLICIT_CAST,
+										exprLocation((Node *) behavior));
+			}
+			else if (typcategory == TYPCATEGORY_BITSTRING)
+			{
+				CoercionContext ccontext;
+				CoercionForm cformat;
+
+				/*
+				 * pg_cast don't have bit & text entry, so in function can_coerce_type
+				 * cannot implilcit cast to text then cast to varbit.
+				 * but we can unknown cast to bit via implilcit cast.
+				 * select '21'::text::bit(2); --fail
+				 * select 21::int4::bit(2); --ok
+				 * so DEFAULT 21 ON ERROR, DEFAULT 11 ON ERROR should be fine;
+				*/
+				if(baseTypmod > 0 && ((exprType(expr) != INT4OID && exprType(expr) != INT8OID)))
+				{
+					ccontext = COERCION_IMPLICIT;
+					cformat = COERCE_IMPLICIT_CAST;
+				}
+				else
+				{
+					ccontext = COERCION_EXPLICIT;
+					cformat = COERCE_EXPLICIT_CAST;
+				}
+				coerced_expr =
+					coerce_to_target_type(pstate, expr, exprType(expr),
+										returning->typid, returning->typmod,
+										ccontext,
+										cformat,
+										exprLocation((Node *) behavior));
+			}
+			else
+				coerced_expr =
+					coerce_to_target_type(pstate, expr, exprType(expr),
+										returning->typid, returning->typmod,
+										COERCION_EXPLICIT, COERCE_EXPLICIT_CAST,
+										exprLocation((Node *) behavior));
 		}
 
 		if (coerced_expr == NULL)
-- 
2.34.1