fix(compiler): Fix compiler crash due to isSkipSelf of null (#30075)

PR Closes https://github.com/angular/angular/issues/27125

PR Close #30075

packages/compiler/src/metadata_resolver.ts

@@ -933,7 +933,7 @@ export class CompileMetadataResolver {
       }
       if (token == null) {
         hasUnknownDeps = true;
-        return null !;
+        return {};
       }
 
       return {
@@ -949,7 +949,7 @@ export class CompileMetadataResolver {
 
     if (hasUnknownDeps) {
       const depsTokens =
-          dependenciesMetadata.map((dep) => dep ? stringifyType(dep.token) : '?').join(', ');
+          dependenciesMetadata.map((dep) => dep.token ? stringifyType(dep.token) : '?').join(', ');
       const message =
           `Can't resolve all parameters for ${stringifyType(typeOrFunc)}: (${depsTokens}).`;
       if (throwOnUnknownDeps || this._config.strictInjectionParameters) {

packages/compiler/test/metadata_resolver_spec.ts

@@ -10,7 +10,7 @@ import {LIFECYCLE_HOOKS_VALUES, LifecycleHooks} from '@angular/compiler/src/life
 import {AfterContentChecked, AfterContentInit, AfterViewChecked, AfterViewInit, ChangeDetectionStrategy, Component, Directive, DoCheck, Injectable, NgModule, OnChanges, OnDestroy, OnInit, Pipe, SimpleChanges, ViewEncapsulation, ɵstringify as stringify} from '@angular/core';
 import {TestBed, async, inject} from '@angular/core/testing';
 
-import {identifierName} from '../src/compile_metadata';
+import {CompileDiDependencyMetadata, identifierName} from '../src/compile_metadata';
 import {CompileMetadataResolver} from '../src/metadata_resolver';
 import {ResourceLoader} from '../src/resource_loader';
 import {MockResourceLoader} from '../testing/src/resource_loader_mock';
@@ -371,6 +371,38 @@ import {TEST_COMPILER_PROVIDERS} from './test_bindings';
              .toThrowError(`SimpleService cannot be used as an entry component.`);
        }));
 
+    it('should generate an error when a dependency could not be resolved',
+       inject([CompileMetadataResolver], (resolver: CompileMetadataResolver) => {
+
+         // Override the errorCollector so that error gets collected instead of
+         // being thrown.
+         (resolver as any)._errorCollector = (error: Error, type?: any) => {
+           expect(error.message).toBe(`Can't resolve all parameters for MyComponent: (?).`);
+         };
+
+         @Component({template: ''})
+         class MyComponent {
+           // @ts-ignore UserService is a non-existent class.
+           constructor(service: UserService) {}
+         }
+
+         @NgModule({declarations: [MyComponent]})
+         class AppModule {
+         }
+
+         const moduleMetadata = resolver.getNgModuleMetadata(AppModule) !;
+         expect(moduleMetadata).toBeTruthy();
+         expect(moduleMetadata.declaredDirectives.length).toBe(1);
+         const directive = moduleMetadata.declaredDirectives[0];
+         const directiveMetadata =
+             resolver.getNonNormalizedDirectiveMetadata(directive.reference) !;
+         expect(directiveMetadata).toBeTruthy();
+         const {metadata} = directiveMetadata;
+         const diDeps: CompileDiDependencyMetadata[] = metadata.type.diDeps;
+         // 'null' does not conform to the shape of `CompileDiDependencyMetadata`
+         expect(diDeps.every(d => d !== null)).toBe(true);
+       }));
+
     it(`should throw an error when a Directive is added to module's bootstrap list`,
        inject([CompileMetadataResolver], (resolver: CompileMetadataResolver) => {