fix(ivy): support listing lazy route for project-root-relative entry point in `ngtsc` (#28542)

I don't know of any use of this API with a project-root-relative path
(i.e. the cli will always call it with an absolute path), but keeping
the API backwards compatible just in case.

PR Close #28542

packages/compiler-cli/src/ngtsc/program.ts

@@ -21,7 +21,7 @@ import {ImportRewriter, ModuleResolver, NoopImportRewriter, R3SymbolsImportRewri
 import {PartialEvaluator} from './partial_evaluator';
 import {TypeScriptReflectionHost} from './reflection';
 import {HostResourceLoader} from './resource_loader';
-import {NgModuleRouteAnalyzer} from './routing';
+import {NgModuleRouteAnalyzer, entryPointKeyFor} from './routing';
 import {FactoryGenerator, FactoryInfo, GeneratedShimsHostWrapper, ShimGenerator, SummaryGenerator, generatedFactoryTransform} from './shims';
 import {ivySwitchTransform} from './switch';
 import {IvyCompilation, declarationTransformFactory, ivyTransformFactory} from './transform';
@@ -191,6 +191,38 @@ export class NgtscProgram implements api.Program {
   }
 
   listLazyRoutes(entryRoute?: string|undefined): api.LazyRoute[] {
+    if (entryRoute) {
+      // Note:
+      // This resolution step is here to match the implementation of the old `AotCompilerHost` (see
+      // https://github.com/angular/angular/blob/50732e156/packages/compiler-cli/src/transformers/compiler_host.ts#L175-L188).
+      //
+      // `@angular/cli` will always call this API with an absolute path, so the resolution step is
+      // not necessary, but keeping it backwards compatible in case someone else is using the API.
+
+      // Relative entry paths are disallowed.
+      if (entryRoute.startsWith('.')) {
+        throw new Error(
+            `Falied to list lazy routes: Resolution of relative paths (${entryRoute}) is not supported.`);
+      }
+
+      // Non-relative entry paths fall into one of the following categories:
+      // - Absolute system paths (e.g. `/foo/bar/my-project/my-module`), which are unaffected by the
+      //   logic below.
+      // - Paths to enternal modules (e.g. `some-lib`).
+      // - Paths mapped to directories in `tsconfig.json` (e.g. `shared/my-module`).
+      //   (See https://www.typescriptlang.org/docs/handbook/module-resolution.html#path-mapping.)
+      //
+      // In all cases above, the `containingFile` argument is ignored, so we can just take the first
+      // of the root files.
+      const containingFile = this.tsProgram.getRootFileNames()[0];
+      const [entryPath, moduleName] = entryRoute.split('#');
+      const resolved = ts.resolveModuleName(entryPath, containingFile, this.options, this.host);
+
+      if (resolved.resolvedModule) {
+        entryRoute = entryPointKeyFor(resolved.resolvedModule.resolvedFileName, moduleName);
+      }
+    }
+
     this.ensureAnalyzed();
     return this.routeAnalyzer !.listLazyRoutes(entryRoute);
   }

packages/compiler-cli/src/ngtsc/routing/index.ts

@@ -9,3 +9,4 @@
 /// <reference types="node" />
 
 export {LazyRoute, NgModuleRouteAnalyzer} from './src/analyzer';
+export {entryPointKeyFor} from './src/route';

packages/compiler-cli/test/ngtools_api_spec.ts

@@ -37,7 +37,7 @@ describe('ngtools_api (deprecated)', () => {
         export class ErrorComp2 {}
 
         @NgModule({
-          declarations: [ErrorComp2, NonExistentComp],
+          declarations: [ErrorComp2],
           imports: [RouterModule.forRoot([{loadChildren: './child#ChildModule'}])]
         })
         export class MainModule {}
@@ -60,7 +60,7 @@ describe('ngtools_api (deprecated)', () => {
     });
   }
 
-  fixmeIvy('FW-629: ngtsc lists lazy routes').it('should list lazy routes recursively', () => {
+  it('should list lazy routes recursively', () => {
     writeSomeRoutes();
     const {program, host, options} =
         createProgram(['src/main.ts', 'src/child.ts', 'src/child2.ts']);