types/json: fix an over-quoted bug in BinaryJSON.Unquote function (#11934)

expression/builtin_json_test.go

@@ -95,8 +95,10 @@ func (s *testEvaluatorSuite) TestJSONUnquote(c *C) {
 		{`{"a":     "b"}`, `{"a":     "b"}`},
 		{`"hello,\"quoted string\",world"`, `hello,"quoted string",world`},
 		{`"hello,\"宽字符\",world"`, `hello,"宽字符",world`},
-		{`Invalid Json string\tis OK`, `Invalid Json string	is OK`},
+		{`Invalid Json string\tis OK`, `Invalid Json string\tis OK`},
 		{`"1\\u2232\\u22322"`, `1\u2232\u22322`},
+		{`"[{\"x\":\"{\\\"y\\\":12}\"}]"`, `[{"x":"{\"y\":12}"}]`},
+		{`[{\"x\":\"{\\\"y\\\":12}\"}]`, `[{\"x\":\"{\\\"y\\\":12}\"}]`},
 	}
 	dtbl := tblToDtbl(tbl)
 	for _, t := range dtbl {

types/json/binary_functions.go

@@ -66,19 +66,17 @@ func (bj BinaryJSON) Unquote() (string, error) {
 	switch bj.TypeCode {
 	case TypeCodeString:
 		tmp := string(hack.String(bj.GetString()))
-		s, err := unquoteString(tmp)
-		if err != nil {
-			return "", errors.Trace(err)
-		}
-		// Remove prefix and suffix '"'.
-		slen := len(s)
-		if slen > 1 {
-			head, tail := s[0], s[slen-1]
-			if head == '"' && tail == '"' {
-				return s[1 : slen-1], nil
-			}
+		tlen := len(tmp)
+		if tlen < 2 {
+			return tmp, nil
+		}
+		head, tail := tmp[0], tmp[tlen-1]
+		if head == '"' && tail == '"' {
+			// Remove prefix and suffix '"' before unquoting
+			return unquoteString(tmp[1 : tlen-1])
 		}
-		return s, nil
+		// if value is not double quoted, do nothing
+		return tmp, nil
 	default:
 		return bj.String(), nil
 	}

types/json/binary_test.go

@@ -114,6 +114,7 @@ func (s *testJSONSuite) TestBinaryJSONUnquote(c *C) {
 	}{
 		{j: `3`, unquoted: "3"},
 		{j: `"3"`, unquoted: "3"},
+		{j: `"[{\"x\":\"{\\\"y\\\":12}\"}]"`, unquoted: `[{"x":"{\"y\":12}"}]`},
 		{j: `"hello, \"escaped quotes\" world"`, unquoted: "hello, \"escaped quotes\" world"},
 		{j: "\"\\u4f60\"", unquoted: "你"},
 		{j: `true`, unquoted: "true"},