Fix hstore_to_json_loose's detection of valid JSON number values.

We expose a function IsValidJsonNumber that internally calls the lexer
for json numbers. That allows us to use the same test everywhere,
instead of inventing a broken test for hstore conversions. The new
function is also used in datum_to_json, replacing the code that is now
moved to the new function.

Backpatch to 9.3 where hstore_to_json_loose was introduced.

2 files changed, 40 insertions, 7 deletions

diff --git a/src/backend/utils/adt/json.c b/src/backend/utils/adt/json.c
index 53a011d50b4..0873bb3ce15 100644
--- a/src/backend/utils/adt/json.c
+++ b/src/backend/utils/adt/json.c
@@ -164,6 +164,36 @@ lex_expect(JsonParseContext ctx, JsonLexContext *lex, JsonTokenType token)
 	 (c) == '_' || \
 	 IS_HIGHBIT_SET(c))
 
+/* utility function to check if a string is a valid JSON number */
+extern bool
+IsValidJsonNumber(const char * str, int len)
+{
+	bool		numeric_error;
+	JsonLexContext dummy_lex;
+
+
+	/*
+	 * json_lex_number expects a leading  '-' to have been eaten already.
+	 *
+	 * having to cast away the constness of str is ugly, but there's not much
+	 * easy alternative.
+	 */
+	if (*str == '-')
+	{
+		dummy_lex.input = (char *) str + 1;
+		dummy_lex.input_length = len - 1;
+	}
+	else
+	{
+		dummy_lex.input = (char *) str;
+		dummy_lex.input_length = len;
+	}
+
+	json_lex_number(&dummy_lex, dummy_lex.input, &numeric_error);
+
+	return ! numeric_error;
+}
+
 /*
  * Input.
  */
@@ -1306,8 +1336,6 @@ datum_to_json(Datum val, bool is_null, StringInfo result,
 {
 	char	   *outputstr;
 	text	   *jsontext;
-	bool       numeric_error;
-	JsonLexContext dummy_lex;
 
 	if (is_null)
 	{
@@ -1332,12 +1360,10 @@ datum_to_json(Datum val, bool is_null, StringInfo result,
 		case JSONTYPE_NUMERIC:
 			outputstr = OidOutputFunctionCall(outfuncoid, val);
 			/*
-			 * Don't call escape_json here if it's a valid JSON number.
+			 * Don't call escape_json for a non-key if it's a valid JSON
+			 * number.
 			 */
-			dummy_lex.input = *outputstr == '-' ? outputstr + 1 : outputstr;
-			dummy_lex.input_length = strlen(dummy_lex.input);
-			json_lex_number(&dummy_lex, dummy_lex.input, &numeric_error);
-			if (! numeric_error)
+			if (!key_scalar && IsValidJsonNumber(outputstr, strlen(outputstr)))
 				appendStringInfoString(result, outputstr);
 			else
 				escape_json(result, outputstr);
diff --git a/src/include/utils/jsonapi.h b/src/include/utils/jsonapi.h
index e25a0d93d89..dcfe71c29dd 100644
--- a/src/include/utils/jsonapi.h
+++ b/src/include/utils/jsonapi.h
@@ -107,4 +107,11 @@ extern void pg_parse_json(JsonLexContext *lex, JsonSemAction *sem);
  */
 extern JsonLexContext *makeJsonLexContext(text *json, bool need_escapes);
 
+/*
+ * Utility function to check if a string is a valid JSON number.
+ *
+ * str agrument does not need to be nul-terminated.
+ */
+extern bool IsValidJsonNumber(const char * str, int len);
+
 #endif   /* JSONAPI_H */