Adjust pg_parse_json() so that it does not directly ereport().

Instead, it now returns a value indicating either success or the
type of error which occurred. The old behavior is still available
by calling pg_parse_json_or_ereport(). If the new interface is
used, an error can be thrown by passing the return value of
pg_parse_json() to json_ereport_error().

pg_parse_json() can still elog() in can't-happen cases, but it
seems like that issue is best handled separately.

Adjust json_lex() and json_count_array_elements() to return an
error code, too.

This is all in preparation for making the backend's json parser
available to frontend code.

Reviewed and/or tested by Mark Dilger and Andrew Dunstan.

Discussion: http://postgr.es/m/CA+TgmoYfOXhd27MUDGioVh6QtpD0C1K-f6ObSA10AWiHBAL5bA@mail.gmail.com

1 files changed, 43 insertions, 3 deletions

diff --git a/src/include/utils/jsonapi.h b/src/include/utils/jsonapi.h
index bbca121bb72..74dc35c41c6 100644
--- a/src/include/utils/jsonapi.h
+++ b/src/include/utils/jsonapi.h
@@ -33,6 +33,28 @@ typedef enum
 	JSON_TOKEN_END
 } JsonTokenType;
 
+typedef enum
+{
+	JSON_SUCCESS,
+	JSON_ESCAPING_INVALID,
+	JSON_ESCAPING_REQUIRED,
+	JSON_EXPECTED_ARRAY_FIRST,
+	JSON_EXPECTED_ARRAY_NEXT,
+	JSON_EXPECTED_COLON,
+	JSON_EXPECTED_END,
+	JSON_EXPECTED_JSON,
+	JSON_EXPECTED_MORE,
+	JSON_EXPECTED_OBJECT_FIRST,
+	JSON_EXPECTED_OBJECT_NEXT,
+	JSON_EXPECTED_STRING,
+	JSON_INVALID_TOKEN,
+	JSON_UNICODE_CODE_POINT_ZERO,
+	JSON_UNICODE_ESCAPE_FORMAT,
+	JSON_UNICODE_HIGH_ESCAPE,
+	JSON_UNICODE_HIGH_SURROGATE,
+	JSON_UNICODE_LOW_SURROGATE
+} JsonParseErrorType;
+
 
 /*
  * All the fields in this structure should be treated as read-only.
@@ -101,7 +123,14 @@ typedef struct JsonSemAction
  * points to. If the action pointers are NULL the parser
  * does nothing and just continues.
  */
-extern void pg_parse_json(JsonLexContext *lex, JsonSemAction *sem);
+extern JsonParseErrorType pg_parse_json(JsonLexContext *lex,
+										JsonSemAction *sem);
+
+/*
+ * Same thing, but signal errors via ereport(ERROR) instead of returning
+ * a result code.
+ */
+extern void pg_parse_json_or_ereport(JsonLexContext *lex, JsonSemAction *sem);
 
 /* the null action object used for pure validation */
 extern JsonSemAction nullSemAction;
@@ -110,8 +139,13 @@ extern JsonSemAction nullSemAction;
  * json_count_array_elements performs a fast secondary parse to determine the
  * number of elements in passed array lex context. It should be called from an
  * array_start action.
+ *
+ * The return value indicates whether any error occurred, while the number
+ * of elements is stored into *elements (but only if the return value is
+ * JSON_SUCCESS).
  */
-extern int	json_count_array_elements(JsonLexContext *lex);
+extern JsonParseErrorType json_count_array_elements(JsonLexContext *lex,
+													int *elements);
 
 /*
  * constructors for JsonLexContext, with or without strval element.
@@ -128,7 +162,13 @@ extern JsonLexContext *makeJsonLexContextCstringLen(char *json,
 													bool need_escapes);
 
 /* lex one token */
-extern void json_lex(JsonLexContext *lex);
+extern JsonParseErrorType json_lex(JsonLexContext *lex);
+
+/* report an error during json lexing or parsing */
+extern void json_ereport_error(JsonParseErrorType error, JsonLexContext *lex);
+
+/* construct an error detail string for a json error */
+extern char *json_errdetail(JsonParseErrorType error, JsonLexContext *lex);
 
 /*
  * Utility function to check if a string is a valid JSON number.