feat(qwen3-tts-cpp): normalize request language for flexible matching (#10174)

The qwen3-tts.cpp backend honored the request `language` field only via exact lowercase two-letter codes in the C++ language_to_id table, silently defaulting to English for anything else (en-US, EN, english, ...).

Add normalizeLanguage() in the Go handler: lowercase + trim, strip the region/locale suffix (en-US, pt_BR, zh-Hans -> en/pt/zh), and resolve common English full names (english -> en). The canonical codes match the existing C++ table, so no C++ change is needed. Covered by a pure-Go Ginkgo spec. Also document the language field and accepted forms under the Qwen3-TTS docs.

Signed-off-by: Ettore Di Giacinto <mudler@localai.io>

Assisted-by: Claude:claude-opus-4-8 [Claude Code]

Co-authored-by: Ettore Di Giacinto <mudler@localai.io>

backend/go/qwen3-tts-cpp/goqwen3ttscpp.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"os"
 	"path/filepath"
+	"strings"
 
 	"github.com/mudler/LocalAI/pkg/grpc/base"
 	pb "github.com/mudler/LocalAI/pkg/grpc/proto"
@@ -21,6 +22,43 @@ type Qwen3TtsCpp struct {
 	threads int
 }
 
+// languageNameAliases maps common full language names to the canonical
+// two-letter code understood by the C++ language_to_id table.
+var languageNameAliases = map[string]string{
+	"english":    "en",
+	"russian":    "ru",
+	"chinese":    "zh",
+	"japanese":   "ja",
+	"korean":     "ko",
+	"german":     "de",
+	"french":     "fr",
+	"spanish":    "es",
+	"italian":    "it",
+	"portuguese": "pt",
+}
+
+// normalizeLanguage coerces a caller-supplied language into the canonical code
+// the model expects. It lowercases, trims, strips any region/locale suffix
+// (en-US, en_US, ja.JP -> en/ja), and resolves common full names (english -> en).
+// An empty input stays empty so the C++ side applies its English default; an
+// unrecognized value is returned normalized so C++ can log it and default.
+func normalizeLanguage(lang string) string {
+	lang = strings.ToLower(strings.TrimSpace(lang))
+	if lang == "" {
+		return ""
+	}
+
+	// Strip region/locale suffix: keep the segment before the first separator.
+	if i := strings.IndexAny(lang, "-_."); i >= 0 {
+		lang = lang[:i]
+	}
+
+	if code, ok := languageNameAliases[lang]; ok {
+		return code
+	}
+	return lang
+}
+
 func (q *Qwen3TtsCpp) Load(opts *pb.ModelOptions) error {
 	// ModelFile is the model directory path (containing GGUF files)
 	modelDir := opts.ModelFile
@@ -54,7 +92,7 @@ func (q *Qwen3TtsCpp) TTS(req *pb.TTSRequest) error {
 	dst := req.Dst
 	language := ""
 	if req.Language != nil {
-		language = *req.Language
+		language = normalizeLanguage(*req.Language)
 	}
 
 	// Synthesis parameters with sensible defaults

backend/go/qwen3-tts-cpp/language_test.go

@@ -0,0 +1,53 @@
+package main
+
+import (
+	"testing"
+
+	. "github.com/onsi/ginkgo/v2"
+	. "github.com/onsi/gomega"
+)
+
+func TestLanguageNormalization(t *testing.T) {
+	RegisterFailHandler(Fail)
+	RunSpecs(t, "qwen3-tts-cpp language normalization")
+}
+
+var _ = Describe("normalizeLanguage", func() {
+	DescribeTable("maps caller input to the canonical model language code",
+		func(input, expected string) {
+			Expect(normalizeLanguage(input)).To(Equal(expected))
+		},
+		// Canonical codes pass through unchanged
+		Entry("canonical en", "en", "en"),
+		Entry("canonical zh", "zh", "zh"),
+		Entry("canonical pt", "pt", "pt"),
+
+		// Case-insensitive
+		Entry("uppercase", "EN", "en"),
+		Entry("mixed case", "Ja", "ja"),
+
+		// Surrounding whitespace
+		Entry("trims whitespace", "  en  ", "en"),
+
+		// Region/locale stripping
+		Entry("BCP-47 region", "en-US", "en"),
+		Entry("underscore region", "en_US", "en"),
+		Entry("dotted locale", "ja.JP", "ja"),
+		Entry("region + case", "ZH-CN", "zh"),
+
+		// Full-name aliases
+		Entry("english name", "english", "en"),
+		Entry("chinese name cased", "Chinese", "zh"),
+		Entry("japanese name", "japanese", "ja"),
+		Entry("russian name", "russian", "ru"),
+		Entry("portuguese name", "portuguese", "pt"),
+
+		// Empty stays empty (C++ applies the English default)
+		Entry("empty", "", ""),
+		Entry("whitespace only", "   ", ""),
+
+		// Unknown values pass through normalized so C++ can log + default
+		Entry("unknown code", "klingon", "klingon"),
+		Entry("unknown with region", "xx-YY", "xx"),
+	)
+})

docs/content/features/text-to-audio.md

@@ -296,6 +296,28 @@ curl http://localhost:8080/tts -H "Content-Type: application/json" -d '{
    }' | aplay
 ```
 
+#### Language
+
+You can hint the synthesis language with the `language` request field:
+
+```
+curl http://localhost:8080/tts -H "Content-Type: application/json" -d '{
+     "model": "qwen-tts",
+     "input": "Bonjour le monde.",
+     "language": "fr"
+   }' | aplay
+```
+
+Supported languages: `en` (English), `zh` (Chinese), `ru` (Russian), `ja` (Japanese), `ko` (Korean), `de` (German), `fr` (French), `es` (Spanish), `it` (Italian), `pt` (Portuguese).
+
+The value is matched case-insensitively and accepts a few forms for convenience:
+
+- the two-letter code (`fr`, `FR`)
+- a locale/region form, whose region is ignored (`fr-FR`, `pt_BR`, `zh-Hans` → `fr`/`pt`/`zh`)
+- the English full name (`french`, `Portuguese`)
+
+If the field is omitted or the value isn't one of the supported languages, the backend defaults to English.
+
 #### Custom Voice Mode
 
 Qwen3-TTS supports predefined speakers. You can specify a speaker using the `voice` parameter: