enable literal string for code search (#33590)

Close: #33588

---------

Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: Giteabot <teabot@gitea.io>

modules/indexer/code/internal/util_test.go

@@ -0,0 +1,30 @@
+// Copyright 2025 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package internal
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestParseKeywordAsPhrase(t *testing.T) {
+	cases := []struct {
+		keyword  string
+		phrase   string
+		isPhrase bool
+	}{
+		{``, "", false},
+		{`a`, "", false},
+		{`"`, "", false},
+		{`"a`, "", false},
+		{`"a"`, "a", true},
+		{`""\"""`, `"\""`, true},
+	}
+	for _, c := range cases {
+		phrase, isPhrase := ParseKeywordAsPhrase(c.keyword)
+		assert.Equal(t, c.phrase, phrase, "keyword=%q", c.keyword)
+		assert.Equal(t, c.isPhrase, isPhrase, "keyword=%q", c.keyword)
+	}
+}