PLT-5548 Prevent server start if defaultLocate is not available (#5532)

* PLT-5548 Prevent server start if defaultLocate is not available

* Add validation for supported locales

i18n/en.json

@@ -5619,6 +5619,18 @@
     "id": "utils.config.save_config.saving.app_error",
     "translation": "An error occurred while saving the file to {{.Filename}}"
   },
+  {
+    "id": "utils.config.supported_client_locale.app_error",
+    "translation": "Unable to load mattermost configuration file:  DefaultClientLocale must be one of the supported locales"
+  },
+  {
+    "id": "utils.config.supported_server_locale.app_error",
+    "translation": "Unable to load mattermost configuration file:  DefaultServerLocale must be one of the supported locales"
+  },
+  {
+    "id": "utils.config.validate_locale.app_error",
+    "translation": "Unable to load mattermost configuration file:  AvailableLocales must include DefaultClientLocale"
+  },
   {
     "id": "utils.diagnostic.analytics_not_found.app_error",
     "translation": "Analytics not initialized"

utils/config.go

@@ -196,6 +196,10 @@ func LoadConfig(fileName string) {
 		}
 	}
 
+	if err := ValidateLocales(&config); err != nil {
+		panic(T(err.Id))
+	}
+
 	if err := ValidateLdapFilter(&config); err != nil {
 		panic(T(err.Id))
 	}
@@ -387,6 +391,29 @@ func ValidateLdapFilter(cfg *model.Config) *model.AppError {
 	return nil
 }
 
+func ValidateLocales(cfg *model.Config) *model.AppError {
+	locales := GetSupportedLocales()
+	if _, ok := locales[*cfg.LocalizationSettings.DefaultServerLocale]; !ok {
+		return model.NewLocAppError("ValidateLocales", "utils.config.supported_server_locale.app_error", nil, "")
+	}
+
+	if _, ok := locales[*cfg.LocalizationSettings.DefaultClientLocale]; !ok {
+		return model.NewLocAppError("ValidateLocales", "utils.config.supported_client_locale.app_error", nil, "")
+	}
+
+	if len(*cfg.LocalizationSettings.AvailableLocales) > 0 {
+		for _, word := range strings.Split(*cfg.LocalizationSettings.AvailableLocales, ",") {
+			if word == *cfg.LocalizationSettings.DefaultClientLocale {
+				return nil
+			}
+		}
+
+		return model.NewLocAppError("ValidateLocales", "utils.config.validate_locale.app_error", nil, "")
+	}
+
+	return nil
+}
+
 func Desanitize(cfg *model.Config) {
 	if cfg.LdapSettings.BindPassword != nil && *cfg.LdapSettings.BindPassword == model.FAKE_SETTING {
 		*cfg.LdapSettings.BindPassword = *Cfg.LdapSettings.BindPassword

utils/i18n.go

@@ -94,6 +94,10 @@ func GetTranslationsAndLocale(w http.ResponseWriter, r *http.Request) (i18n.Tran
 	return translations, model.DEFAULT_LOCALE
 }
 
+func GetSupportedLocales() map[string]string {
+	return locales
+}
+
 func TfuncWithFallback(pref string) i18n.TranslateFunc {
 	t, _ := i18n.Tfunc(pref)
 	return func(translationID string, args ...interface{}) string {