fix: panic when parsing and extracting JSON key values (#13790)

(cherry picked from commit 5ef83a7)

pkg/logql/log/parser_test.go

@@ -39,6 +39,34 @@ func Test_jsonParser_Parse(t *testing.T) {
 			),
 			NoParserHints(),
 		},
+		{
+			"whitespace key value",
+			[]byte(`{" ": {"foo":"bar"}}`),
+			labels.EmptyLabels(),
+			labels.FromStrings("foo", "bar"),
+			NoParserHints(),
+		},
+		{
+			"whitespace key and whitespace subkey values",
+			[]byte(`{" ": {" ":"bar"}}`),
+			labels.EmptyLabels(),
+			labels.FromStrings("", "bar"),
+			NoParserHints(),
+		},
+		{
+			"whitespace key and empty subkey values",
+			[]byte(`{" ": {"":"bar"}}`),
+			labels.EmptyLabels(),
+			labels.FromStrings("", "bar"),
+			NoParserHints(),
+		},
+		{
+			"empty key and empty subkey values",
+			[]byte(`{"": {"":"bar"}}`),
+			labels.EmptyLabels(),
+			labels.FromStrings("", "bar"),
+			NoParserHints(),
+		},
 		{
 			"escaped",
 			[]byte(`{"counter":1,"foo":"foo\\\"bar", "price": {"_net_":5.56909}}`),

pkg/logql/log/util.go

@@ -40,10 +40,11 @@ func sanitizeLabelKey(key string, isPrefix bool) string {
 
 // appendSanitize appends the sanitized key to the slice.
 func appendSanitized(to, key []byte) []byte {
+	key = bytes.TrimSpace(key)
+
 	if len(key) == 0 {
 		return to
 	}
-	key = bytes.TrimSpace(key)
 
 	if len(to) == 0 && key[0] >= '0' && key[0] <= '9' {
 		to = append(to, '_')