fix(ivy): ensure overrides for 'multi: true' only appear once in final providers

packages/core/test/test_bed_spec.ts

@@ -225,10 +225,77 @@ describe('TestBed', () => {
   });
 
   it('allow to override a provider', () => {
-    TestBed.overrideProvider(NAME, {useValue: 'injected World !'});
+    TestBed.overrideProvider(NAME, {useValue: 'injected World!'});
     const hello = TestBed.createComponent(HelloWorld);
     hello.detectChanges();
-    expect(hello.nativeElement).toHaveText('Hello injected World !');
+    expect(hello.nativeElement).toHaveText('Hello injected World!');
+  });
+
+  it('uses the most recent provider override', () => {
+    TestBed.overrideProvider(NAME, {useValue: 'injected World!'});
+    TestBed.overrideProvider(NAME, {useValue: 'injected World a second time!'});
+    const hello = TestBed.createComponent(HelloWorld);
+    hello.detectChanges();
+    expect(hello.nativeElement).toHaveText('Hello injected World a second time!');
+  });
+
+  it('overrides a providers in an array', () => {
+    TestBed.configureTestingModule({
+      imports: [HelloWorldModule],
+      providers: [
+        [{provide: NAME, useValue: 'injected World!'}],
+      ]
+    });
+    TestBed.overrideProvider(NAME, {useValue: 'injected World a second time!'});
+    const hello = TestBed.createComponent(HelloWorld);
+    hello.detectChanges();
+    expect(hello.nativeElement).toHaveText('Hello injected World a second time!');
+  });
+
+  describe('multi providers', () => {
+    const multiToken = new InjectionToken<string[]>('multiToken');
+    const singleToken = new InjectionToken<string>('singleToken');
+    @NgModule({providers: [{provide: multiToken, useValue: 'valueFromModule', multi: true}]})
+    class MyModule {
+    }
+
+    @NgModule({
+      providers: [
+        {provide: singleToken, useValue: 't1'},
+        {provide: multiToken, useValue: 'valueFromModule2', multi: true},
+        {provide: multiToken, useValue: 'secondValueFromModule2', multi: true}
+      ]
+    })
+    class MyModule2 {
+    }
+
+    beforeEach(() => { TestBed.configureTestingModule({imports: [MyModule, MyModule2]}); });
+
+    it('is preserved when other provider is overridden', () => {
+      TestBed.overrideProvider(singleToken, {useValue: ''});
+      const value = TestBed.inject(multiToken);
+      expect(value.length).toEqual(3);
+    });
+
+    it('overridden with an array', () => {
+      const overrideValue = ['override'];
+      TestBed.overrideProvider(multiToken, { useValue: overrideValue, multi: true } as any);
+
+      const value = TestBed.inject(multiToken);
+      expect(value.length).toEqual(overrideValue.length);
+      expect(value).toEqual(overrideValue);
+    });
+
+    it('overridden with a non-array', () => {
+      // This is actually invalid because multi providers return arrays. We have this here so we can
+      // ensure Ivy behaves the same as VE does currently.
+      const overrideValue = 'override';
+      TestBed.overrideProvider(multiToken, { useValue: overrideValue, multi: true } as any);
+
+      const value = TestBed.inject(multiToken);
+      expect(value.length).toEqual(overrideValue.length);
+      expect(value).toEqual(overrideValue as {} as string[]);
+    });
   });
 
   it('should allow overriding a provider defined via ModuleWithProviders (using TestBed.overrideProvider)',

packages/core/testing/src/r3_test_bed_compiler.ts

@@ -159,7 +159,7 @@ export class R3TestBedCompiler {
           provide: token,
           useFactory: provider.useFactory,
           deps: provider.deps || [],
-          multi: provider.multi,
+          multi: provider.multi
         } :
         {provide: token, useValue: provider.useValue, multi: provider.multi};
 
@@ -619,34 +619,23 @@ export class R3TestBedCompiler {
   private getOverriddenProviders(providers?: Provider[]): Provider[] {
     if (!providers || !providers.length || this.providerOverridesByToken.size === 0) return [];
 
-    const overrides = this.getProviderOverrides(providers);
-    const hasMultiProviderOverrides = overrides.some(isMultiProvider);
-    const overriddenProviders = [...providers, ...overrides];
-
-    // No additional processing is required in case we have no multi providers to override
-    if (!hasMultiProviderOverrides) {
-      return overriddenProviders;
-    }
-
+    const flattenedProviders = flatten<Provider[]>(providers);
+    const overrides = this.getProviderOverrides(flattenedProviders);
+    const overriddenProviders = [...flattenedProviders, ...overrides];
     const final: Provider[] = [];
     const seenMultiProviders = new Set<Provider>();
 
     // We iterate through the list of providers in reverse order to make sure multi provider
-    // overrides take precedence over the values defined in provider list. We also fiter out all
+    // overrides take precedence over the values defined in provider list. We also filter out all
     // multi providers that have overrides, keeping overridden values only.
     forEachRight(overriddenProviders, (provider: any) => {
       const token: any = getProviderToken(provider);
       if (isMultiProvider(provider) && this.providerOverridesByToken.has(token)) {
+        // Don't add overridden multi-providers twice because when you override a multi-provider, we
+        // treat it as `{multi: false}` to avoid providing the same value multiple times.
         if (!seenMultiProviders.has(token)) {
           seenMultiProviders.add(token);
-          if (provider && provider.useValue && Array.isArray(provider.useValue)) {
-            forEachRight(provider.useValue, (value: any) => {
-              // Unwrap provider override array into individual providers in final set.
-              final.unshift({provide: token, useValue: value, multi: true});
-            });
-          } else {
-            final.unshift(provider);
-          }
+          final.unshift({...provider, multi: false});
         }
       } else {
         final.unshift(provider);