feat(ivy): allow the locale to be set via a global property (#33314)

In the post-$localize world the current locale value is defined by setting
`$localize.locale` which is then read at runtime by Angular in the provider
for the `LOCALE_ID` token and also passed to the ivy machinery via`setLocaleId()`.

The $localize compile-time inlining tooling can replace occurrences of
`$localize.locale` with a string literal, similar to how translations
are inlined.

// FW-1639

See https://github.com/angular/angular-cli/issues/15896

PR Close #33314

packages/core/test/application_module_spec.ts

@@ -7,11 +7,74 @@
  */
 
 import {LOCALE_ID} from '@angular/core';
+import {ivyEnabled} from '@angular/private/testing';
+
+import {getLocaleId} from '../src/render3';
+import {global} from '../src/util/global';
+import {TestBed} from '../testing';
 import {describe, expect, inject, it} from '../testing/src/testing_internal';
 
 {
   describe('Application module', () => {
     it('should set the default locale to "en-US"',
        inject([LOCALE_ID], (defaultLocale: string) => { expect(defaultLocale).toEqual('en-US'); }));
+
+    if (ivyEnabled) {
+      it('should set the ivy locale with the configured LOCALE_ID', () => {
+        TestBed.configureTestingModule({providers: [{provide: LOCALE_ID, useValue: 'fr'}]});
+        const before = getLocaleId();
+        const locale = TestBed.inject(LOCALE_ID);
+        const after = getLocaleId();
+        expect(before).toEqual('en-us');
+        expect(locale).toEqual('fr');
+        expect(after).toEqual('fr');
+      });
+
+      describe('$localize.locale', () => {
+        beforeEach(() => initLocale('de'));
+        afterEach(() => restoreLocale());
+
+        it('should set the ivy locale to `$localize.locale` value if it is defined', () => {
+          // Injecting `LOCALE_ID` should also initialize the ivy locale
+          const locale = TestBed.inject(LOCALE_ID);
+          expect(locale).toEqual('de');
+          expect(getLocaleId()).toEqual('de');
+        });
+
+        it('should set the ivy locale to an application provided LOCALE_ID even if `$localize.locale` is defined',
+           () => {
+             TestBed.configureTestingModule({providers: [{provide: LOCALE_ID, useValue: 'fr'}]});
+             const locale = TestBed.inject(LOCALE_ID);
+             expect(locale).toEqual('fr');
+             expect(getLocaleId()).toEqual('fr');
+           });
+      });
+    }
   });
 }
+
+let hasGlobalLocalize: boolean;
+let hasGlobalLocale: boolean;
+let originalLocale: string;
+
+function initLocale(locale: string) {
+  hasGlobalLocalize = Object.getOwnPropertyNames(global).includes('$localize');
+  if (!hasGlobalLocalize) {
+    global.$localize = {};
+  }
+  hasGlobalLocale = Object.getOwnPropertyNames(global.$localize).includes('locale');
+  originalLocale = global.$localize.locale;
+  global.$localize.locale = locale;
+}
+
+function restoreLocale() {
+  if (hasGlobalLocale) {
+    global.$localize.locale = originalLocale;
+  } else {
+    delete global.$localize.locale;
+  }
+
+  if (!hasGlobalLocalize) {
+    delete global.$localize;
+  }
+}