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

5 files changed, 342 insertions, 283 deletions

diff --git a/src/backend/utils/adt/json.c b/src/backend/utils/adt/json.c
index 4be16b5c20..e73a60ece8 100644
--- a/src/backend/utils/adt/json.c
+++ b/src/backend/utils/adt/json.c
@@ -81,7 +81,7 @@ json_in(PG_FUNCTION_ARGS)
 
 	/* validate it */
 	lex = makeJsonLexContext(result, false);
-	pg_parse_json(lex, &nullSemAction);
+	pg_parse_json_or_ereport(lex, &nullSemAction);
 
 	/* Internal representation is the same as text, for now */
 	PG_RETURN_TEXT_P(result);
@@ -128,7 +128,7 @@ json_recv(PG_FUNCTION_ARGS)
 
 	/* Validate it. */
 	lex = makeJsonLexContextCstringLen(str, nbytes, false);
-	pg_parse_json(lex, &nullSemAction);
+	pg_parse_json_or_ereport(lex, &nullSemAction);
 
 	PG_RETURN_TEXT_P(cstring_to_text_with_len(str, nbytes));
 }
@@ -1337,12 +1337,15 @@ json_typeof(PG_FUNCTION_ARGS)
 	JsonLexContext *lex;
 	JsonTokenType tok;
 	char	   *type;
+	JsonParseErrorType	result;
 
 	json = PG_GETARG_TEXT_PP(0);
 	lex = makeJsonLexContext(json, false);
 
 	/* Lex exactly one token from the input and check its type. */
-	json_lex(lex);
+	result = json_lex(lex);
+	if (result != JSON_SUCCESS)
+		json_ereport_error(result, lex);
 	tok = lex->token_type;
 	switch (tok)
 	{
diff --git a/src/backend/utils/adt/jsonapi.c b/src/backend/utils/adt/jsonapi.c
index 9e14306b6f..129fbd65d5 100644
--- a/src/backend/utils/adt/jsonapi.c
+++ b/src/backend/utils/adt/jsonapi.c
@@ -35,18 +35,17 @@ typedef enum					/* contexts of JSON parser */
 	JSON_PARSE_END				/* saw the end of a document, expect nothing */
 } JsonParseContext;
 
-static inline void json_lex_string(JsonLexContext *lex);
-static inline void json_lex_number(JsonLexContext *lex, char *s,
+static inline JsonParseErrorType json_lex_string(JsonLexContext *lex);
+static inline JsonParseErrorType json_lex_number(JsonLexContext *lex, char *s,
 								   bool *num_err, int *total_len);
-static inline void parse_scalar(JsonLexContext *lex, JsonSemAction *sem);
-static void parse_object_field(JsonLexContext *lex, JsonSemAction *sem);
-static void parse_object(JsonLexContext *lex, JsonSemAction *sem);
-static void parse_array_element(JsonLexContext *lex, JsonSemAction *sem);
-static void parse_array(JsonLexContext *lex, JsonSemAction *sem);
-static void report_parse_error(JsonParseContext ctx, JsonLexContext *lex) pg_attribute_noreturn();
-static void report_invalid_token(JsonLexContext *lex) pg_attribute_noreturn();
+static inline JsonParseErrorType parse_scalar(JsonLexContext *lex, JsonSemAction *sem);
+static JsonParseErrorType parse_object_field(JsonLexContext *lex, JsonSemAction *sem);
+static JsonParseErrorType parse_object(JsonLexContext *lex, JsonSemAction *sem);
+static JsonParseErrorType parse_array_element(JsonLexContext *lex, JsonSemAction *sem);
+static JsonParseErrorType parse_array(JsonLexContext *lex, JsonSemAction *sem);
+static JsonParseErrorType report_parse_error(JsonParseContext ctx, JsonLexContext *lex);
 static int	report_json_context(JsonLexContext *lex);
-static char *extract_mb_char(char *s);
+static char *extract_token(JsonLexContext *lex);
 
 /* the null action object used for pure validation */
 JsonSemAction nullSemAction =
@@ -74,13 +73,13 @@ lex_peek(JsonLexContext *lex)
  * move the lexer to the next token if the current look_ahead token matches
  * the parameter token. Otherwise, report an error.
  */
-static inline void
+static inline JsonParseErrorType
 lex_expect(JsonParseContext ctx, JsonLexContext *lex, JsonTokenType token)
 {
 	if (lex_peek(lex) == token)
-		json_lex(lex);
+		return json_lex(lex);
 	else
-		report_parse_error(ctx, lex);
+		return report_parse_error(ctx, lex);
 }
 
 /* chars to consider as part of an alphanumeric token */
@@ -171,13 +170,16 @@ makeJsonLexContextCstringLen(char *json, int len, bool need_escapes)
  * action routines to be called at appropriate spots during parsing, and a
  * pointer to a state object to be passed to those routines.
  */
-void
+JsonParseErrorType
 pg_parse_json(JsonLexContext *lex, JsonSemAction *sem)
 {
 	JsonTokenType tok;
+	JsonParseErrorType	result;
 
 	/* get the initial token */
-	json_lex(lex);
+	result = json_lex(lex);
+	if (result != JSON_SUCCESS)
+		return result;
 
 	tok = lex_peek(lex);
 
@@ -185,17 +187,36 @@ pg_parse_json(JsonLexContext *lex, JsonSemAction *sem)
 	switch (tok)
 	{
 		case JSON_TOKEN_OBJECT_START:
-			parse_object(lex, sem);
+			result = parse_object(lex, sem);
 			break;
 		case JSON_TOKEN_ARRAY_START:
-			parse_array(lex, sem);
+			result = parse_array(lex, sem);
 			break;
 		default:
-			parse_scalar(lex, sem); /* json can be a bare scalar */
+			result = parse_scalar(lex, sem); /* json can be a bare scalar */
 	}
 
-	lex_expect(JSON_PARSE_END, lex, JSON_TOKEN_END);
+	if (result == JSON_SUCCESS)
+		result = lex_expect(JSON_PARSE_END, lex, JSON_TOKEN_END);
+
+	return result;
+}
+
+/*
+ * pg_parse_json_or_ereport
+ *
+ * This fuction is like pg_parse_json, except that it does not return a
+ * JsonParseErrorType. Instead, in case of any failure, this function will
+ * ereport(ERROR).
+ */
+void
+pg_parse_json_or_ereport(JsonLexContext *lex, JsonSemAction *sem)
+{
+	JsonParseErrorType	result;
 
+	result = pg_parse_json(lex, sem);
+	if (result != JSON_SUCCESS)
+		json_ereport_error(result, lex);
 }
 
 /*
@@ -206,11 +227,12 @@ pg_parse_json(JsonLexContext *lex, JsonSemAction *sem)
  *
  * Designed to be called from array_start routines.
  */
-int
-json_count_array_elements(JsonLexContext *lex)
+JsonParseErrorType
+json_count_array_elements(JsonLexContext *lex, int *elements)
 {
 	JsonLexContext copylex;
 	int			count;
+	JsonParseErrorType	result;
 
 	/*
 	 * It's safe to do this with a shallow copy because the lexical routines
@@ -222,21 +244,32 @@ json_count_array_elements(JsonLexContext *lex)
 	copylex.lex_level++;
 
 	count = 0;
-	lex_expect(JSON_PARSE_ARRAY_START, &copylex, JSON_TOKEN_ARRAY_START);
+	result = lex_expect(JSON_PARSE_ARRAY_START, &copylex,
+						JSON_TOKEN_ARRAY_START);
+	if (result != JSON_SUCCESS)
+		return result;
 	if (lex_peek(&copylex) != JSON_TOKEN_ARRAY_END)
 	{
 		while (1)
 		{
 			count++;
-			parse_array_element(&copylex, &nullSemAction);
+			result = parse_array_element(&copylex, &nullSemAction);
+			if (result != JSON_SUCCESS)
+				return result;
 			if (copylex.token_type != JSON_TOKEN_COMMA)
 				break;
-			json_lex(&copylex);
+			result = json_lex(&copylex);
+			if (result != JSON_SUCCESS)
+				return result;
 		}
 	}
-	lex_expect(JSON_PARSE_ARRAY_NEXT, &copylex, JSON_TOKEN_ARRAY_END);
+	result = lex_expect(JSON_PARSE_ARRAY_NEXT, &copylex,
+							JSON_TOKEN_ARRAY_END);
+	if (result != JSON_SUCCESS)
+		return result;
 
-	return count;
+	*elements = count;
+	return JSON_SUCCESS;
 }
 
 /*
@@ -248,25 +281,23 @@ json_count_array_elements(JsonLexContext *lex)
  *	  - object ( { } )
  *	  - object field
  */
-static inline void
+static inline JsonParseErrorType
 parse_scalar(JsonLexContext *lex, JsonSemAction *sem)
 {
 	char	   *val = NULL;
 	json_scalar_action sfunc = sem->scalar;
 	JsonTokenType tok = lex_peek(lex);
+	JsonParseErrorType result;
 
 	/* a scalar must be a string, a number, true, false, or null */
 	if (tok != JSON_TOKEN_STRING && tok != JSON_TOKEN_NUMBER &&
 		tok != JSON_TOKEN_TRUE && tok != JSON_TOKEN_FALSE &&
 		tok != JSON_TOKEN_NULL)
-		report_parse_error(JSON_PARSE_VALUE, lex);
+		return report_parse_error(JSON_PARSE_VALUE, lex);
 
 	/* if no semantic function, just consume the token */
 	if (sfunc == NULL)
-	{
-		json_lex(lex);
-		return;
-	}
+		return json_lex(lex);
 
 	/* extract the de-escaped string value, or the raw lexeme */
 	if (lex_peek(lex) == JSON_TOKEN_STRING)
@@ -284,13 +315,17 @@ parse_scalar(JsonLexContext *lex, JsonSemAction *sem)
 	}
 
 	/* consume the token */
-	json_lex(lex);
+	result = json_lex(lex);
+	if (result != JSON_SUCCESS)
+		return result;
 
 	/* invoke the callback */
 	(*sfunc) (sem->semstate, val, tok);
+
+	return JSON_SUCCESS;
 }
 
-static void
+static JsonParseErrorType
 parse_object_field(JsonLexContext *lex, JsonSemAction *sem)
 {
 	/*
@@ -304,14 +339,19 @@ parse_object_field(JsonLexContext *lex, JsonSemAction *sem)
 	json_ofield_action oend = sem->object_field_end;
 	bool		isnull;
 	JsonTokenType tok;
+	JsonParseErrorType result;
 
 	if (lex_peek(lex) != JSON_TOKEN_STRING)
-		report_parse_error(JSON_PARSE_STRING, lex);
+		return report_parse_error(JSON_PARSE_STRING, lex);
 	if ((ostart != NULL || oend != NULL) && lex->strval != NULL)
 		fname = pstrdup(lex->strval->data);
-	json_lex(lex);
+	result = json_lex(lex);
+	if (result != JSON_SUCCESS)
+		return result;
 
-	lex_expect(JSON_PARSE_OBJECT_LABEL, lex, JSON_TOKEN_COLON);
+	result = lex_expect(JSON_PARSE_OBJECT_LABEL, lex, JSON_TOKEN_COLON);
+	if (result != JSON_SUCCESS)
+		return result;
 
 	tok = lex_peek(lex);
 	isnull = tok == JSON_TOKEN_NULL;
@@ -322,20 +362,23 @@ parse_object_field(JsonLexContext *lex, JsonSemAction *sem)
 	switch (tok)
 	{
 		case JSON_TOKEN_OBJECT_START:
-			parse_object(lex, sem);
+			result = parse_object(lex, sem);
 			break;
 		case JSON_TOKEN_ARRAY_START:
-			parse_array(lex, sem);
+			result = parse_array(lex, sem);
 			break;
 		default:
-			parse_scalar(lex, sem);
+			result = parse_scalar(lex, sem);
 	}
+	if (result != JSON_SUCCESS)
+		return result;
 
 	if (oend != NULL)
 		(*oend) (sem->semstate, fname, isnull);
+	return JSON_SUCCESS;
 }
 
-static void
+static JsonParseErrorType
 parse_object(JsonLexContext *lex, JsonSemAction *sem)
 {
 	/*
@@ -345,6 +388,7 @@ parse_object(JsonLexContext *lex, JsonSemAction *sem)
 	json_struct_action ostart = sem->object_start;
 	json_struct_action oend = sem->object_end;
 	JsonTokenType tok;
+	JsonParseErrorType result;
 
 	check_stack_depth();
 
@@ -360,40 +404,51 @@ parse_object(JsonLexContext *lex, JsonSemAction *sem)
 	lex->lex_level++;
 
 	Assert(lex_peek(lex) == JSON_TOKEN_OBJECT_START);
-	json_lex(lex);
+	result = json_lex(lex);
+	if (result != JSON_SUCCESS)
+		return result;
 
 	tok = lex_peek(lex);
 	switch (tok)
 	{
 		case JSON_TOKEN_STRING:
-			parse_object_field(lex, sem);
-			while (lex_peek(lex) == JSON_TOKEN_COMMA)
+			result = parse_object_field(lex, sem);
+			while (result == JSON_SUCCESS && lex_peek(lex) == JSON_TOKEN_COMMA)
 			{
-				json_lex(lex);
-				parse_object_field(lex, sem);
+				result = json_lex(lex);
+				if (result != JSON_SUCCESS)
+					break;
+				result = parse_object_field(lex, sem);
 			}
 			break;
 		case JSON_TOKEN_OBJECT_END:
 			break;
 		default:
 			/* case of an invalid initial token inside the object */
-			report_parse_error(JSON_PARSE_OBJECT_START, lex);
+			result = report_parse_error(JSON_PARSE_OBJECT_START, lex);
 	}
+	if (result != JSON_SUCCESS)
+		return result;
 
-	lex_expect(JSON_PARSE_OBJECT_NEXT, lex, JSON_TOKEN_OBJECT_END);
+	result = lex_expect(JSON_PARSE_OBJECT_NEXT, lex, JSON_TOKEN_OBJECT_END);
+	if (result != JSON_SUCCESS)
+		return result;
 
 	lex->lex_level--;
 
 	if (oend != NULL)
 		(*oend) (sem->semstate);
+
+	return JSON_SUCCESS;
 }
 
-static void
+static JsonParseErrorType
 parse_array_element(JsonLexContext *lex, JsonSemAction *sem)
 {
 	json_aelem_action astart = sem->array_element_start;
 	json_aelem_action aend = sem->array_element_end;
 	JsonTokenType tok = lex_peek(lex);
+	JsonParseErrorType result;
 
 	bool		isnull;
 
@@ -406,20 +461,25 @@ parse_array_element(JsonLexContext *lex, JsonSemAction *sem)
 	switch (tok)
 	{
 		case JSON_TOKEN_OBJECT_START:
-			parse_object(lex, sem);
+			result = parse_object(lex, sem);
 			break;
 		case JSON_TOKEN_ARRAY_START:
-			parse_array(lex, sem);
+			result = parse_array(lex, sem);
 			break;
 		default:
-			parse_scalar(lex, sem);
+			result = parse_scalar(lex, sem);
 	}
 
+	if (result != JSON_SUCCESS)
+		return result;
+
 	if (aend != NULL)
 		(*aend) (sem->semstate, isnull);
+
+	return JSON_SUCCESS;
 }
 
-static void
+static JsonParseErrorType
 parse_array(JsonLexContext *lex, JsonSemAction *sem)
 {
 	/*
@@ -428,6 +488,7 @@ parse_array(JsonLexContext *lex, JsonSemAction *sem)
 	 */
 	json_struct_action astart = sem->array_start;
 	json_struct_action aend = sem->array_end;
+	JsonParseErrorType result;
 
 	check_stack_depth();
 
@@ -442,35 +503,43 @@ parse_array(JsonLexContext *lex, JsonSemAction *sem)
 	 */
 	lex->lex_level++;
 
-	lex_expect(JSON_PARSE_ARRAY_START, lex, JSON_TOKEN_ARRAY_START);
-	if (lex_peek(lex) != JSON_TOKEN_ARRAY_END)
+	result = lex_expect(JSON_PARSE_ARRAY_START, lex, JSON_TOKEN_ARRAY_START);
+	if (result == JSON_SUCCESS && lex_peek(lex) != JSON_TOKEN_ARRAY_END)
 	{
+		result = parse_array_element(lex, sem);
 
-		parse_array_element(lex, sem);
-
-		while (lex_peek(lex) == JSON_TOKEN_COMMA)
+		while (result == JSON_SUCCESS && lex_peek(lex) == JSON_TOKEN_COMMA)
 		{
-			json_lex(lex);