Fix copy-paste error in datum_to_jsonb_internal()

Commit 3c152a27b06 mistakenly repeated JSONTYPE_JSON in a condition,
omitting JSONTYPE_CAST. As a result, datum_to_jsonb_internal() failed
to reject inputs that were casts (e.g., from an enum to json as in the
example below) when used as keys in JSON constructors.

This led to a crash in cases like:

  SELECT JSON_OBJECT('happy'::mood: '123'::jsonb);

where 'happy'::mood is implicitly cast to json. The missing check
meant such casted values weren’t properly rejected as invalid
(non-scalar) JSON keys.

Reported-by: Maciek Sakrejda <maciek@pganalyze.com>
Reviewed-by: Tender Wang <tndrwang@gmail.com>
Reviewed-by: Alvaro Herrera <alvherre@alvh.no-ip.org>
Reviewed-by: Maciek Sakrejda <maciek@pganalyze.com>
Discussion: https://postgr.es/m/CADXhmgTJtJZK9A3Na_ry+Xrq-ghjcejBRhcRMzWZvbd__QdgJA@mail.gmail.com
Backpatch-through: 17

1 files changed, 11 insertions, 0 deletions

diff --git a/src/test/regress/sql/sqljson.sql b/src/test/regress/sql/sqljson.sql
index 9b5d82602d0..3fd6ac260b8 100644
--- a/src/test/regress/sql/sqljson.sql
+++ b/src/test/regress/sql/sqljson.sql
@@ -152,6 +152,17 @@ SELECT JSON_OBJECT(1: 1, '2': NULL, '1': 1 ABSENT ON NULL WITH UNIQUE RETURNING
 SELECT JSON_OBJECT(1: 1, '2': NULL, '1': 1 ABSENT ON NULL WITHOUT UNIQUE RETURNING jsonb);
 SELECT JSON_OBJECT(1: 1, '2': NULL, '3': 1, 4: NULL, '5': 'a' ABSENT ON NULL WITH UNIQUE RETURNING jsonb);
 
+-- BUG: https://postgr.es/m/CADXhmgTJtJZK9A3Na_ry%2BXrq-ghjcejBRhcRMzWZvbd__QdgJA%40mail.gmail.com
+-- datum_to_jsonb_internal() didn't catch keys that are casts instead of a simple scalar
+CREATE TYPE mood AS ENUM ('happy', 'sad', 'neutral');
+CREATE FUNCTION mood_to_json(mood) RETURNS json AS $$
+  SELECT to_json($1::text);
+$$ LANGUAGE sql IMMUTABLE;
+CREATE CAST (mood AS json) WITH FUNCTION mood_to_json(mood) AS IMPLICIT;
+SELECT JSON_OBJECT('happy'::mood: '123'::jsonb);
+DROP CAST (mood AS json);
+DROP FUNCTION mood_to_json;
+DROP TYPE mood;
 
 -- JSON_ARRAY()
 SELECT JSON_ARRAY();