fix: fallback locales default not overwritten

Author: Sergio Moreno

packages/conf/src/index.test.ts

@@ -165,7 +165,7 @@ describe("@lingui/conf", function () {
       })
     })
 
-    it ("if fallbackLocales is defined, we also build the cldr", () => {
+    it ("if fallbackLocales default is defined, we dont build the cldr", () => {
       const config = getConfig({
         configPath: path.resolve(
           __dirname,
@@ -175,7 +175,6 @@ describe("@lingui/conf", function () {
       expect(config.fallbackLocales).toEqual({
         "en-US": ["en"],
         default: "en",
-        "es-MX": "es"
       })
     })
   })

packages/conf/src/index.ts

@@ -305,22 +305,24 @@ export function fallbackLanguageMigration(
       fallbackLocales: null,
     }
 
-  config.locales.forEach((locale) => {
-    const fl = getCldrParentLocale(locale.toLowerCase())
-    if (fl && !config.fallbackLocales[locale]) {
-      config.fallbackLocales = {
-        ...config.fallbackLocales,
-        [locale]: fl,
-      }
-    }
-  })
-
   const DEFAULT_FALLBACK = fallbackLocales?.default || fallbackLocale
   if (DEFAULT_FALLBACK) {
     if (!config.fallbackLocales) config.fallbackLocales = {}
     config.fallbackLocales.default = DEFAULT_FALLBACK
   }
 
+  if (config.fallbackLocales !== false && !config.fallbackLocales.default) {
+    config.locales.forEach((locale) => {
+      const fl = getCldrParentLocale(locale.toLowerCase())
+      if (fl && !config.fallbackLocales[locale]) {
+        config.fallbackLocales = {
+          ...config.fallbackLocales,
+          [locale]: fl,
+        }
+      }
+    })
+  }
+
   return config
 }