Properly detect invalid JSON numbers when generating JSON.

adunstan · adunstan · commit 4825a9e95fbc · 2013-12-27T17:21:27.000-05:00
Instead of looking for characters that aren't valid in JSON numbers, we
simply pass the output string through the JSON number parser, and if it
fails the string is quoted. This means among other things that money and
domains over money will be quoted correctly and generate valid JSON.

Fixes bug #8676 reported by Anderson Cristian da Silva.

Backpatched to 9.2 where JSON generation was introduced.
diff --git a/src/backend/utils/adt/json.c b/src/backend/utils/adt/json.c
@@ -73,7 +73,7 @@ typedef enum					/* required operations on state stack */
 static void json_validate_cstring(char *input);
 static void json_lex(JsonLexContext *lex);
 static void json_lex_string(JsonLexContext *lex);
-static void json_lex_number(JsonLexContext *lex, char *s);
+static void json_lex_number(JsonLexContext *lex, char *s, bool *num_err);
 static void report_parse_error(JsonParseStack *stack, JsonLexContext *lex);
 static void report_invalid_token(JsonLexContext *lex);
 static int report_json_context(JsonLexContext *lex);
@@ -89,8 +89,6 @@ static void array_to_json_internal(Datum array, StringInfo result,
 
 /* fake type category for JSON so we can distinguish it in datum_to_json */
 #define TYPCATEGORY_JSON 'j'
-/* letters appearing in numeric output that aren't valid in a JSON number */
-#define NON_NUMERIC_LETTER "NnAaIiFfTtYy"
 /* chars to consider as part of an alphanumeric token */
 #define JSON_ALPHANUMERIC_CHAR(c)  \
 	(((c) >= 'a' && (c) <= 'z') || \
@@ -361,13 +359,13 @@ json_lex(JsonLexContext *lex)
 	else if (*s == '-')
 	{
 		/* Negative number. */
-		json_lex_number(lex, s + 1);
+		json_lex_number(lex, s + 1, NULL);
 		lex->token_type = JSON_VALUE_NUMBER;
 	}
 	else if (*s >= '0' && *s <= '9')
 	{
 		/* Positive number. */
-		json_lex_number(lex, s);
+		json_lex_number(lex, s, NULL);
 		lex->token_type = JSON_VALUE_NUMBER;
 	}
 	else
@@ -530,7 +528,7 @@ json_lex_string(JsonLexContext *lex)
  *-------------------------------------------------------------------------
  */
 static void
-json_lex_number(JsonLexContext *lex, char *s)
+json_lex_number(JsonLexContext *lex, char *s, bool *num_err)
 {
 	bool		error = false;
 	char	   *p;
@@ -584,15 +582,24 @@ json_lex_number(JsonLexContext *lex, char *s)
 	}
 
 	/*
-	 * Check for trailing garbage.  As in json_lex(), any alphanumeric stuff
+	 * Check for trailing garbage.	As in json_lex(), any alphanumeric stuff
 	 * here should be considered part of the token for error-reporting
 	 * purposes.
 	 */
 	for (p = s; JSON_ALPHANUMERIC_CHAR(*p); p++)
 		error = true;
-	lex->token_terminator = p;
-	if (error)
-		report_invalid_token(lex);
+
+	if (num_err != NULL)
+	{
+		/* let the caller handle the error */
+		*num_err = error;
+	}
+	else
+	{
+		lex->token_terminator = p;
+		if (error)
+			report_invalid_token(lex);
+	}
 }
 
 /*
@@ -819,6 +826,8 @@ datum_to_json(Datum val, bool is_null, StringInfo result,
 			  TYPCATEGORY tcategory, Oid typoutputfunc)
 {
 	char	   *outputstr;
+	bool		numeric_error;
+	JsonLexContext dummy_lex;
 
 	if (is_null)
 	{
@@ -845,11 +854,10 @@ datum_to_json(Datum val, bool is_null, StringInfo result,
 
 			/*
 			 * Don't call escape_json here if it's a valid JSON number.
-			 * Numeric output should usually be a valid JSON number and JSON
-			 * numbers shouldn't be quoted. Quote cases like "Nan" and
-			 * "Infinity", however.
 			 */
-			if (strpbrk(outputstr, NON_NUMERIC_LETTER) == NULL)
+			dummy_lex.input = *outputstr == '-' ? outputstr + 1 : outputstr;
+			json_lex_number(&dummy_lex, dummy_lex.input, &numeric_error);
+			if (!numeric_error)
 				appendStringInfoString(result, outputstr);
 			else
 				escape_json(result, outputstr);
