feat(core): add option for lazy loaded modules to extend translations

Fixes #425

README.md

@@ -87,6 +87,10 @@ export class SharedModule { }
 When you lazy load a module, you should use the `forChild` static method to import the `TranslateModule`.
 
 Since lazy loaded modules use a different injector from the rest of your application, you can configure them separately with a different loader/compiler/parser/missing translations handler.
+
+To make a child module extend translations from parent modules use `extend: true`. This will cause the service to also
+use translations from its parent module.
+
 You can also isolate the service by using `isolate: true`. In which case the service is a completely isolated instance (for translations, current lang, events, ...).
 Otherwise, by default, it will share its data with other instances of the service (but you can still use a different loader/compiler/parser/handler even if you don't isolate the service).
 

projects/ngx-translate/core/src/lib/translate.service.ts

@@ -11,6 +11,7 @@ import {isDefined, mergeDeep} from "./util";
 
 export const USE_STORE = new InjectionToken<string>('USE_STORE');
 export const USE_DEFAULT_LANG = new InjectionToken<string>('USE_DEFAULT_LANG');
+export const USE_EXTEND = new InjectionToken<string>('USE_EXTEND');
 
 export interface TranslationChangeEvent {
   translations: any;
@@ -152,7 +153,8 @@ export class TranslateService {
               public parser: TranslateParser,
               public missingTranslationHandler: MissingTranslationHandler,
               @Inject(USE_DEFAULT_LANG) private useDefaultLang: boolean = true,
-              @Inject(USE_STORE) private isolate: boolean = false) {
+              @Inject(USE_STORE) private isolate: boolean = false,
+              @Inject(USE_EXTEND) private extend: boolean = false) {
   }
 
   /**
@@ -223,8 +225,8 @@ export class TranslateService {
   private retrieveTranslations(lang: string): Observable<any> {
     let pending: Observable<any>;
 
-    // if this language is unavailable, ask for it
-    if (typeof this.translations[lang] === "undefined") {
+    // if this language is unavailable or extend is true, ask for it
+    if (typeof this.translations[lang] === "undefined" || this.extend) {
       this._translationRequests[lang] = this._translationRequests[lang] || this.getTranslation(lang);
       pending = this._translationRequests[lang];
     }
@@ -252,7 +254,7 @@ export class TranslateService {
     this.loadingTranslations
       .subscribe({
         next: (res: Object) => {
-          this.translations[lang] = res;
+          this.translations[lang] = this.extend && this.translations[lang] ? { ...res, ...this.translations[lang] } : res;
           this.updateLangs();
           this.pending = false;
         },
@@ -270,7 +272,7 @@ export class TranslateService {
    */
   public setTranslation(lang: string, translations: Object, shouldMerge: boolean = false): void {
     translations = this.compiler.compileTranslations(translations, lang);
-    if (shouldMerge && this.translations[lang]) {
+    if ((shouldMerge || this.extend) && this.translations[lang]) {
       this.translations[lang] = mergeDeep(this.translations[lang], translations);
     } else {
       this.translations[lang] = translations;

projects/ngx-translate/core/src/public_api.ts

@@ -8,6 +8,7 @@ import {TranslateDirective} from "./lib/translate.directive";
 import {TranslatePipe} from "./lib/translate.pipe";
 import {TranslateStore} from "./lib/translate.store";
 import {USE_STORE} from "./lib/translate.service";
+import {USE_EXTEND} from "./lib/translate.service";
 import {USE_DEFAULT_LANG} from "./lib/translate.service";
 
 export * from "./lib/translate.loader";
@@ -26,6 +27,8 @@ export interface TranslateModuleConfig {
   missingTranslationHandler?: Provider;
   // isolate the service instance, only works for lazy loaded modules or components with the "providers" property
   isolate?: boolean;
+  // extends translations for a given language instead of ignoring them if present
+  extend?: boolean;
   useDefaultLang?: boolean;
 }
 
@@ -54,6 +57,7 @@ export class TranslateModule {
         TranslateStore,
         {provide: USE_STORE, useValue: config.isolate},
         {provide: USE_DEFAULT_LANG, useValue: config.useDefaultLang},
+        {provide: USE_EXTEND, useValue: config.extend},
         TranslateService
       ]
     };
@@ -72,6 +76,7 @@ export class TranslateModule {
         config.missingTranslationHandler || {provide: MissingTranslationHandler, useClass: FakeMissingTranslationHandler},
         {provide: USE_STORE, useValue: config.isolate},
         {provide: USE_DEFAULT_LANG, useValue: config.useDefaultLang},
+        {provide: USE_EXTEND, useValue: config.extend},
         TranslateService
       ]
     };

projects/ngx-translate/core/tests/translate.store.spec.ts

@@ -12,7 +12,10 @@ import {TranslateModule, TranslateService} from "../src/public_api";
 })
 class RootCmp {
   constructor(public translate: TranslateService) {
-    translate.setTranslation('en', {"TEST": "Root"});
+    translate.setTranslation('en', {
+      "TEST": "Root",
+      'ROOT': 'Root'
+    });
     translate.use('en');
   }
 }
@@ -28,7 +31,10 @@ function getLazyLoadedModule(importedModule: ModuleWithProviders) {
   @Component({selector: 'lazy', template: 'lazy-loaded-child'})
   class ChildLazyLoadedComponent {
     constructor(public translate: TranslateService) {
-      translate.setTranslation('en', {"TEST": "Lazy"});
+      translate.setTranslation('en', {
+        "TEST": "Lazy",
+        'CHILD': 'Child'
+      });
       translate.use('en');
       expect(translate.instant('TEST')).toEqual('Lazy');
     }
@@ -197,4 +203,24 @@ describe("module", () => {
       sub.unsubscribe();
     }))
   );
+
+  it('should extend translations with extend true', fakeAsync(inject(
+    [Router, Location, NgModuleFactoryLoader],
+    (router: Router, location: Location, loader: SpyNgModuleFactoryLoader) => {
+      let loadedModule = getLazyLoadedModule(TranslateModule.forChild({ extend: true }));
+      loader.stubbedModules = { expected: loadedModule };
+
+      const fixture = createRoot(router, RootCmp);
+      const translate: TranslateService = TestBed.get(TranslateService);
+
+      router.resetConfig([{path: 'lazy', loadChildren: 'expected'}]);
+
+      router.navigateByUrl('/lazy/loaded/child');
+      advance(fixture);
+
+      expect(translate.instant('TEST')).toEqual('Lazy');
+      expect(translate.instant('ROOT')).toEqual('Root');
+      expect(translate.instant('CHILD')).toEqual('Child');
+    }))
+  );
 });