Remove ill-conceived ban on zero length json object keys.

We removed a similar ban on this in json_object recently, but the ban in
datum_to_json was left, which generate4d sprutious errors in othee json
generators, notable json_build_object.

Along the way, add an assertion that datum_to_json is not passed a null
key. All current callers comply with this rule, but the assertion will
catch any possible future misbehaviour.

diff --git a/src/backend/utils/adt/json.c b/src/backend/utils/adt/json.c
index c52f6732b054b626d93efa44ffad854c72c84332..6f678eb8b2232a7685e4d8d908ce334a5ece9c54 100644 (file)
--- a/src/backend/utils/adt/json.c
+++ b/src/backend/utils/adt/json.c
@@ -1342,6 +1342,9 @@ datum_to_json(Datum val, bool is_null, StringInfo result,
    bool        numeric_error;
    JsonLexContext dummy_lex;
 
+   /* callers are expected to ensure that null keys are not passed in */
+   Assert( ! (key_scalar && is_null));
+
    if (is_null)
    {
        appendStringInfoString(result, "null");
@@ -1487,10 +1490,6 @@ datum_to_json(Datum val, bool is_null, StringInfo result,
            break;
        default:
            outputstr = OidOutputFunctionCall(outfuncoid, val);
-           if (key_scalar && *outputstr == '\0')
-               ereport(ERROR,
-                       (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
-                        errmsg("key value must not be empty")));
            escape_json(result, outputstr);
            pfree(outputstr);
            break;