Fix non-ASCII search on database (go-gitea#18437)

Use `ToASCIIUpper` for SQLite database on issues search, this because `UPPER(x)` on SQLite only transforms ASCII letters. Resolves go-gitea#18429

models/issue.go

@@ -23,6 +23,7 @@ import (
 	"code.gitea.io/gitea/modules/git"
 	"code.gitea.io/gitea/modules/log"
 	"code.gitea.io/gitea/modules/references"
+	"code.gitea.io/gitea/modules/setting"
 	api "code.gitea.io/gitea/modules/structs"
 	"code.gitea.io/gitea/modules/timeutil"
 	"code.gitea.io/gitea/modules/util"
@@ -1862,7 +1863,12 @@ func GetRepoIssueStats(repoID, uid int64, filterMode int, isPull bool) (numOpen,
 func SearchIssueIDsByKeyword(ctx context.Context, kw string, repoIDs []int64, limit, start int) (int64, []int64, error) {
 	repoCond := builder.In("repo_id", repoIDs)
 	subQuery := builder.Select("id").From("issue").Where(repoCond)
-	kw = strings.ToUpper(kw)
+	// SQLite's UPPER function only transforms ASCII letters.
+	if setting.Database.UseSQLite3 {
+		kw = util.ToUpperASCII(kw)
+	} else {
+		kw = strings.ToUpper(kw)
+	}
 	cond := builder.And(
 		repoCond,
 		builder.Or(

modules/util/util.go

@@ -170,3 +170,14 @@ func CryptoRandomBytes(length int64) ([]byte, error) {
 	_, err := rand.Read(buf)
 	return buf, err
 }
+
+// ToUpperASCII returns s with all ASCII letters mapped to their upper case.
+func ToUpperASCII(s string) string {
+	b := []byte(s)
+	for i, c := range b {
+		if 'a' <= c && c <= 'z' {
+			b[i] -= 'a' - 'A'
+		}
+	}
+	return string(b)
+}

modules/util/util_test.go

@@ -186,3 +186,37 @@ func Test_OptionalBool(t *testing.T) {
 	assert.Equal(t, OptionalBoolTrue, OptionalBoolParse("t"))
 	assert.Equal(t, OptionalBoolTrue, OptionalBoolParse("True"))
 }
+
+// Test case for any function which accepts and returns a single string.
+type StringTest struct {
+	in, out string
+}
+
+var upperTests = []StringTest{
+	{"", ""},
+	{"ONLYUPPER", "ONLYUPPER"},
+	{"abc", "ABC"},
+	{"AbC123", "ABC123"},
+	{"azAZ09_", "AZAZ09_"},
+	{"longStrinGwitHmixofsmaLLandcAps", "LONGSTRINGWITHMIXOFSMALLANDCAPS"},
+	{"long\u0250string\u0250with\u0250nonascii\u2C6Fchars", "LONG\u0250STRING\u0250WITH\u0250NONASCII\u2C6FCHARS"},
+	{"\u0250\u0250\u0250\u0250\u0250", "\u0250\u0250\u0250\u0250\u0250"},
+	{"a\u0080\U0010FFFF", "A\u0080\U0010FFFF"},
+	{"lél", "LéL"},
+}
+
+func TestToUpperASCII(t *testing.T) {
+	for _, tc := range upperTests {
+		assert.Equal(t, ToUpperASCII(tc.in), tc.out)
+	}
+}
+
+func BenchmarkToUpper(b *testing.B) {
+	for _, tc := range upperTests {
+		b.Run(tc.in, func(b *testing.B) {
+			for i := 0; i < b.N; i++ {
+				ToUpperASCII(tc.in)
+			}
+		})
+	}
+}