Code review for error reports in jsonb_set().

User-facing (even tested by regression tests) error conditions were thrown
with elog(), hence had wrong SQLSTATE and were untranslatable.  And the
error message texts weren't up to project style, either.

src/backend/utils/adt/jsonfuncs.c

@@ -3722,12 +3722,15 @@ setPath(JsonbIterator **it, Datum *path_elems,
 {
 	JsonbValue	v;
 	JsonbIteratorToken r;
-	JsonbValue *res = NULL;
+	JsonbValue *res;
 
 	check_stack_depth();
 
 	if (path_nulls[level])
-		elog(ERROR, "path element at the position %d is NULL", level + 1);
+		ereport(ERROR,
+				(errcode(ERRCODE_NULL_VALUE_NOT_ALLOWED),
+				 errmsg("path element at position %d is null",
+						level + 1)));
 
 	r = JsonbIteratorNext(it, &v, false);
 
@@ -3740,7 +3743,6 @@ setPath(JsonbIterator **it, Datum *path_elems,
 			r = JsonbIteratorNext(it, &v, false);
 			Assert(r == WJB_END_ARRAY);
 			res = pushJsonbValue(st, r, NULL);
-
 			break;
 		case WJB_BEGIN_OBJECT:
 			(void) pushJsonbValue(st, r, NULL);
@@ -3749,14 +3751,15 @@ setPath(JsonbIterator **it, Datum *path_elems,
 			r = JsonbIteratorNext(it, &v, true);
 			Assert(r == WJB_END_OBJECT);
 			res = pushJsonbValue(st, r, NULL);
-
 			break;
 		case WJB_ELEM:
 		case WJB_VALUE:
 			res = pushJsonbValue(st, r, &v);
 			break;
 		default:
-			elog(ERROR, "impossible state");
+			elog(ERROR, "unrecognized iterator result: %d", (int) r);
+			res = NULL;			/* keep compiler quiet */
+			break;
 	}
 
 	return res;
@@ -3867,7 +3870,6 @@ setPathArray(JsonbIterator **it, Datum *path_elems, bool *path_nulls,
 	JsonbValue	v;
 	int			idx,
 				i;
-	char	   *badp;
 	bool		done = false;
 
 	/* pick correct index */
@@ -3875,14 +3877,17 @@ setPathArray(JsonbIterator **it, Datum *path_elems, bool *path_nulls,
 	{
 		char	   *c = TextDatumGetCString(path_elems[level]);
 		long		lindex;
+		char	   *badp;
 
 		errno = 0;
 		lindex = strtol(c, &badp, 10);
 		if (errno != 0 || badp == c || *badp != '\0' || lindex > INT_MAX ||
 			lindex < INT_MIN)
-			elog(ERROR, "path element at the position %d is not an integer", level + 1);
-		else
-			idx = lindex;
+			ereport(ERROR,
+					(errcode(ERRCODE_INVALID_TEXT_REPRESENTATION),
+			  errmsg("path element at position %d is not an integer: \"%s\"",
+					 level + 1, c)));
+		idx = lindex;
 	}
 	else
 		idx = nelems;
@@ -3957,7 +3962,6 @@ setPathArray(JsonbIterator **it, Datum *path_elems, bool *path_nulls,
 			{
 				addJsonbToParseState(st, newval);
 			}
-
 		}
 	}
 }

src/test/regress/expected/jsonb.out

@@ -3114,7 +3114,7 @@ select jsonb_set('{"n":null, "a":1, "b":[1,2], "c":{"1":2}, "d":{"1":[2,3]}}'::j
 (1 row)
 
 select jsonb_set('{"n":null, "a":1, "b":[1,2], "c":{"1":2}, "d":{"1":[2,3]}}'::jsonb, '{d,NULL,0}', '[1,2,3]');
-ERROR:  path element at the position 2 is NULL
+ERROR:  path element at position 2 is null
 select jsonb_set('{"n":null, "a":1, "b":[1,2], "c":{"1":2}, "d":{"1":[2,3]}}'::jsonb, '{n}', '{"1": 2}');
                                 jsonb_set                                
 -------------------------------------------------------------------------
@@ -3134,7 +3134,7 @@ select jsonb_set('{"n":null, "a":1, "b":[1,2], "c":{"1":2}, "d":{"1":[2,3]}}'::j
 (1 row)
 
 select jsonb_set('{"n":null, "a":1, "b":[1,2], "c":{"1":2}, "d":{"1":[2,3]}}'::jsonb, '{d,NULL,0}', '{"1": 2}');
-ERROR:  path element at the position 2 is NULL
+ERROR:  path element at position 2 is null
 select jsonb_set('{"n":null, "a":1, "b":[1,2], "c":{"1":2}, "d":{"1":[2,3]}}'::jsonb, '{b,-1}', '"test"');
                                 jsonb_set                                 
 --------------------------------------------------------------------------
@@ -3178,7 +3178,7 @@ select '{"n":null, "a":1, "b":[1,2], "c":{"1":2}, "d":{"1":[2,3]}}'::jsonb #- '{
 (1 row)
 
 select '{"n":null, "a":1, "b":[1,2], "c":{"1":2}, "d":{"1":[2,3]}}'::jsonb #- '{b,-1e}'; -- invalid array subscript
-ERROR:  path element at the position 2 is not an integer
+ERROR:  path element at position 2 is not an integer: "-1e"
 select '{"n":null, "a":1, "b":[1,2], "c":{"1":2}, "d":{"1":[2,3]}}'::jsonb #- '{d,1,0}';
                              ?column?                             
 ------------------------------------------------------------------
@@ -3307,8 +3307,8 @@ select jsonb_set('[]','{-99}','{"foo":123}');
 (1 row)
 
 select jsonb_set('{"a": [1, 2, 3]}', '{a, non_integer}', '"new_value"');
-ERROR:  path element at the position 2 is not an integer
+ERROR:  path element at position 2 is not an integer: "non_integer"
 select jsonb_set('{"a": {"b": [1, 2, 3]}}', '{a, b, non_integer}', '"new_value"');
-ERROR:  path element at the position 3 is not an integer
+ERROR:  path element at position 3 is not an integer: "non_integer"
 select jsonb_set('{"a": {"b": [1, 2, 3]}}', '{a, b, NULL}', '"new_value"');
-ERROR:  path element at the position 3 is NULL
+ERROR:  path element at position 3 is null