localise.go

@@ -114,7 +114,12 @@ func CurrentPluralCategory(n int) PluralCategory {
 }
 
 func detectLanguage(supported []language.Tag) string {
-	for _, langEnv := range []string{os.Getenv("LC_ALL"), os.Getenv("LC_MESSAGES"), os.Getenv("LANG")} {
+	for _, langEnv := range []string{
+		os.Getenv("LC_ALL"),
+		firstLocaleFromList(os.Getenv("LANGUAGE")),
+		os.Getenv("LC_MESSAGES"),
+		os.Getenv("LANG"),
+	} {
 		if langEnv == "" {
 			continue
 		}
@@ -145,6 +150,18 @@ func detectLanguageFromEnv(langEnv string, supported []language.Tag) string {
 	return bestMatch.String()
 }
 
+func firstLocaleFromList(langList string) string {
+	if langList == "" {
+		return ""
+	}
+	for _, lang := range core.Split(langList, ":") {
+		if trimmed := core.Trim(lang); trimmed != "" {
+			return trimmed
+		}
+	}
+	return ""
+}
+
 func normalizeLanguageTag(lang string) string {
 	lang = core.Trim(lang)
 	if lang == "" {

localise_test.go

@@ -279,6 +279,20 @@ func TestDetectLanguage_SkipsInvalidHigherPriorityLocale(t *testing.T) {
 	assert.Equal(t, "fr", result, "invalid LC_ALL should not block a valid lower-priority locale")
 }
 
+func TestDetectLanguage_PrefersLanguageList(t *testing.T) {
+	t.Setenv("LANGUAGE", "fr_FR.UTF-8:de_DE.UTF-8")
+	t.Setenv("LANG", "en_US.UTF-8")
+
+	supported := []language.Tag{
+		language.AmericanEnglish,
+		language.French,
+		language.German,
+	}
+
+	result := detectLanguage(supported)
+	assert.Equal(t, "fr", result, "LANGUAGE should be considered before LANG")
+}
+
 // --- Mode.String() ---
 
 func TestMode_String_Good(t *testing.T) {