Put unescaped regexes in a raw string literal (#10331)

pkg/logql/log/label_filter.go

@@ -368,6 +368,16 @@ type lineFilterLabelFilter struct {
 	filter Filterer
 }
 
+// overrides the matcher.String() function in case there is a regexpFilter
+func (s *lineFilterLabelFilter) String() string {
+	if unwrappedFilter, ok := s.filter.(regexpFilter); ok {
+		rStr := unwrappedFilter.String()
+		str := fmt.Sprintf("%s%s`%s`", s.Matcher.Name, s.Matcher.Type, rStr)
+		return str
+	}
+	return s.Matcher.String()
+}
+
 func (s *lineFilterLabelFilter) Process(_ int64, line []byte, lbs *LabelsBuilder) ([]byte, bool) {
 	v := labelValue(s.Name, lbs)
 	return line, s.filter.Filter(unsafeGetBytes(v))

pkg/logql/syntax/parser_test.go

@@ -3465,3 +3465,22 @@ func TestNoOpLabelToString(t *testing.T) {
 	require.NoError(t, err)
 	require.Len(t, stages, 0)
 }
+
+func TestParseSampleExpr_String(t *testing.T) {
+	t.Run("it doesn't add escape characters when after getting parsed", func(t *testing.T) {
+		query := `sum(rate({cluster="beep", namespace="boop"} | msg=~` + "`" + `.*?(GET|POST|PUT|DELETE|PATCH|HEAD|OPTIONS) /loki/api/(?i)(\d+[a-z]|[a-z]+\d)\w*/query_range` + "`" + `[1d]))`
+		expr, err := ParseSampleExpr(query)
+		require.NoError(t, err)
+
+		require.Equal(t, query, expr.String())
+	})
+
+	t.Run("it removes escape characters after being parsed", func(t *testing.T) {
+		query := `{cluster="beep", namespace="boop"} | msg=~"\\w.*"`
+		expr, err := ParseExpr(query)
+		require.NoError(t, err)
+
+		// escaping is hard: the result is {cluster="beep", namespace="boop"} | msg=~`\w.*` which is equivalent to the original
+		require.Equal(t, "{cluster=\"beep\", namespace=\"boop\"} | msg=~`\\w.*`", expr.String())
+	})
+}