feat(core): implement hierarchical translation services with parent-child lookup

  BREAKING CHANGE: TranslateModule.forRoot() and forChild() are removed.
  Use provideTranslateService() and provideChildTranslateService() instead.

  - Add parent-child service hierarchy with translation lookup bubbling
  - provideTranslateService() creates isolated root services (isRoot=true)
  - provideChildTranslateService() creates connected children that:
    - Delegate lang/fallbackLang to root
    - Load own translations via provided loader
    - Fall back to parent when translation not found
  - MissingTranslationHandler resolution bubbles up hierarchy
  - Simplify TranslateStore to only manage translations
  - Move lang/fallback state management to TranslateService
  - Replace `extend` config with clearer `isRoot` semantic

  Migration:
  - TranslateModule.forRoot() → provideTranslateService()
  - TranslateModule.forChild({ extend: true }) → provideChildTranslateService()
  - TranslateModule.forChild({ isolate: true }) → provideTranslateService()

Author: CodeAndWeb

docs/proposal-providers-and-scoping.md

@@ -32,37 +32,4 @@ export interface TranslateModuleConfig extends TranslateProviders {
     imports: [TranslatePipe, TranslateDirective],
     exports: [TranslatePipe, TranslateDirective],
 })
-export class TranslateModule {
-    /**
-     * Use this method in your root module to provide the TranslateService
-     */
-    static forRoot(config: TranslateModuleConfig = {}): ModuleWithProviders<TranslateModule> {
-        return {
-            ngModule: TranslateModule,
-            providers: [
-                ...defaultProviders(
-                    {
-                        compiler: provideTranslateCompiler(TranslateNoOpCompiler),
-                        parser: provideTranslateParser(TranslateDefaultParser),
-                        loader: provideTranslateLoader(TranslateNoOpLoader),
-                        missingTranslationHandler: provideMissingTranslationHandler(
-                            DefaultMissingTranslationHandler,
-                        ),
-                        ...config,
-                    },
-                    true,
-                ),
-            ],
-        };
-    }
-
-    /**
-     * Use this method in your other (non-root) modules to import the directive/pipe
-     */
-    static forChild(config: TranslateModuleConfig = {}): ModuleWithProviders<TranslateModule> {
-        return {
-            ngModule: TranslateModule,
-            providers: [...defaultProviders(config, config.isolate ?? false)],
-        };
-    }
-}
+export class TranslateModule { }

projects/ngx-translate/src/lib/translate.module.ts

@@ -1,4 +1,4 @@
-import { ClassProvider, Provider, Type } from "@angular/core";
+import { ClassProvider, inject, InjectionToken, Provider, Type } from "@angular/core";
 import {
     DefaultMissingTranslationHandler,
     MissingTranslationHandler,
@@ -21,13 +21,12 @@ export interface TranslateProviders {
     missingTranslationHandler?: Provider;
 }
 
-export interface ChildTranslateServiceConfig extends Partial<TranslateProviders> {
-    extend?: boolean;
-}
+export interface ChildTranslateServiceConfig extends Partial<TranslateProviders> { }
 
 export interface RootTranslateServiceConfig extends ChildTranslateServiceConfig {
     fallbackLang?: Language;
     lang?: Language;
+    isRoot?: boolean;
 
     /* @deprecated use `fallbackLang` */
     useDefaultLang?: boolean;
@@ -63,13 +62,26 @@ export function provideTranslateService(config: RootTranslateServiceConfig = {})
                 DefaultMissingTranslationHandler,
             ),
             ...config,
+            isRoot: true,
         },
         true,
     );
 }
 
 export function provideChildTranslateService(config: ChildTranslateServiceConfig = {}): Provider[] {
-    return defaultProviders({ extend: true, ...config }, false);
+    return defaultProviders(
+        {
+            compiler: provideTranslateCompiler(TranslateNoOpCompiler),
+            parser: provideTranslateParser(TranslateDefaultParser),
+            loader: provideTranslateLoader(TranslateNoOpLoader),
+            missingTranslationHandler: provideMissingTranslationHandler(
+                DefaultMissingTranslationHandler,
+            ),
+            ...config,
+            isRoot: false,
+        },
+        true,
+    );
 }
 
 export function defaultProviders(
@@ -108,7 +120,7 @@ export function defaultProviders(
     const serviceConfig: TranslateServiceConfig = {
         fallbackLang: config.fallbackLang ?? null,
         lang: config.lang,
-        extend: config.extend ?? false,
+        isRoot: config.isRoot ?? false,
     };
 
     providers.push({
@@ -119,14 +131,6 @@ export function defaultProviders(
     providers.push({
         provide: TranslateService,
         useClass: TranslateService,
-        deps: [
-            TranslateStore,
-            TranslateLoader,
-            TranslateCompiler,
-            TranslateParser,
-            MissingTranslationHandler,
-            TRANSLATE_SERVICE_CONFIG,
-        ],
     });
 
     return providers;