fix(i18n): bug loading the default locale correctly

fix #167

Author: pikax

packages/core/__tests__/i18n/i18n.spec.ts

@@ -100,4 +100,19 @@ describe("i18n", () => {
       expect((x.i18n.value as any).hello).toBeUndefined();
     });
   });
+
+  it("should fallback if the locale is different than fallback locale", async () => {
+    const x = buildI18n({
+      locale: "jp",
+      fallback: "en",
+      messages: {
+        en: { hello: "Hello" },
+        jp: {}
+      }
+    });
+
+    await nextTick();
+
+    expect((x.i18n.value as any).hello).toBe("Hello");
+  });
 });

packages/core/src/i18n/i18n.ts

@@ -134,7 +134,10 @@ export function buildI18n<
 
   let fallbackIsPromise = false;
   if (shouldFallback) {
-    const fallbackI18n = loadLocale(locale.value as string, localeMessages);
+    const fallbackI18n = loadLocale(
+      definition.fallback! as string,
+      localeMessages
+    );
     if (isPromise(fallbackI18n)) {
       fallbackI18n.then(x => {
         fallback = x;
@@ -147,7 +150,7 @@ export function buildI18n<
     fallback.value = {};
   }
 
-  watch(
+  watch(  
     [locale, fallback],
     async ([l, fb]: [keyof TMessage, i18n | undefined]) => {
       if (l === definition.fallback && shouldFallback) {