refactor(@angular/build): move compiler-cli loading to TypeScriptCompilation

AngularCompilation serves as the top-level compilation contract used across the build pipeline, including on the main thread via ParallelCompilation. Neither AngularCompilation nor ParallelCompilation requires loading @angular/compiler-cli or reading tsconfig.json configurations.

The loadCompilerCli and loadConfiguration methods are now moved to TypeScriptCompilation, which is the base class for in-process TypeScript compilations (AotCompilation and JitCompilation). This completely decouples AngularCompilation from @angular/compiler-cli and ensures that compiler-cli loading and configuration parsing are localized exclusively to the worker compilation hierarchy.

Author: clydin

packages/angular/build/src/tools/angular/compilation/angular-compilation.ts

@@ -6,9 +6,7 @@
  * found in the LICENSE file at https://angular.dev/license
  */
 
-import type * as ng from '@angular/compiler-cli';
 import type { PartialMessage } from 'esbuild';
-import { profileSync } from '../../esbuild/profiling';
 import type { AngularHostOptions } from '../angular-host';
 import type { CompilerOptionOverrides } from './compiler-options';
 
@@ -50,37 +48,6 @@ export enum DiagnosticModes {
 }
 
 export abstract class AngularCompilation {
-  static #angularCompilerCliModule?: typeof ng;
-
-  static async loadCompilerCli(): Promise<typeof ng> {
-    AngularCompilation.#angularCompilerCliModule ??= await import('@angular/compiler-cli');
-
-    return AngularCompilation.#angularCompilerCliModule;
-  }
-
-  protected async loadConfiguration(tsconfig: string): Promise<ng.CompilerOptions> {
-    const { readConfiguration } = await AngularCompilation.loadCompilerCli();
-
-    return profileSync('NG_READ_CONFIG', () =>
-      readConfiguration(tsconfig, {
-        // Angular specific configuration defaults and overrides to ensure a functioning compilation.
-        suppressOutputPathCheck: true,
-        outDir: undefined,
-        sourceMap: false,
-        declaration: false,
-        declarationMap: false,
-        allowEmptyCodegenFiles: false,
-        annotationsAs: 'decorators',
-        enableResourceInlining: false,
-        supportTestBed: false,
-        supportJitMode: false,
-        // Disable removing of comments as TS is quite aggressive with these and can
-        // remove important annotations, such as /* @__PURE__ */ and comments like /* vite-ignore */.
-        removeComments: false,
-      }),
-    );
-  }
-
   abstract initialize(
     tsconfig: string,
     hostOptions: AngularHostOptions,

packages/angular/build/src/tools/angular/compilation/angular-compilation_spec.ts

@@ -128,6 +128,12 @@ describe('AngularCompilation', () => {
       await compilation.update?.(new Set(['/src/test.ts']));
       expect(compilation.getCachedSourceFiles().has('/src/test.ts')).toBeFalse();
     });
+
+    it('dynamically loads the @angular/compiler-cli module', async () => {
+      const compilerCli = await TypeScriptCompilation.loadCompilerCli();
+      expect(compilerCli).toBeDefined();
+      expect(typeof compilerCli.readConfiguration).toBe('function');
+    });
   });
 
   describe('createAngularCompilation', () => {

packages/angular/build/src/tools/angular/compilation/aot-compilation.ts

@@ -22,10 +22,9 @@ import { replaceBootstrap } from '../transformers/jit-bootstrap-transformer';
 import { lazyRoutesTransformer } from '../transformers/lazy-routes-transformer';
 import { createWorkerTransformer } from '../transformers/web-worker-transformer';
 import {
-  AngularCompilation,
-  AngularCompilationResult,
+  type AngularCompilationResult,
   DiagnosticModes,
-  EmitFileResult,
+  type EmitFileResult,
 } from './angular-compilation';
 import { CompilerOptionOverrides, transformCompilerOptions } from './compiler-options';
 import { collectHmrCandidates } from './hmr-candidates';
@@ -69,7 +68,7 @@ export class AotCompilation extends TypeScriptCompilation {
     compilerOptionOverrides?: CompilerOptionOverrides,
   ): Promise<AngularCompilationResult> {
     // Dynamically load the Angular compiler CLI package
-    const { NgtscProgram, OptimizeFor } = await AngularCompilation.loadCompilerCli();
+    const { NgtscProgram, OptimizeFor } = await TypeScriptCompilation.loadCompilerCli();
 
     // Load the compiler configuration and transform as needed
     const {

packages/angular/build/src/tools/angular/compilation/jit-compilation.ts

@@ -16,10 +16,9 @@ import { createJitResourceTransformer } from '../transformers/jit-resource-trans
 import { lazyRoutesTransformer } from '../transformers/lazy-routes-transformer';
 import { createWorkerTransformer } from '../transformers/web-worker-transformer';
 import {
-  AngularCompilation,
-  AngularCompilationResult,
+  type AngularCompilationResult,
   DiagnosticModes,
-  EmitFileResult,
+  type EmitFileResult,
 } from './angular-compilation';
 import { CompilerOptionOverrides, transformCompilerOptions } from './compiler-options';
 import { TypeScriptCompilation } from './typescript-compilation';

packages/angular/build/src/tools/angular/compilation/typescript-compilation.ts

@@ -6,14 +6,46 @@
  * found in the LICENSE file at https://angular.dev/license
  */
 
+import type * as ng from '@angular/compiler-cli';
 import type { PartialMessage } from 'esbuild';
 import ts from 'typescript';
 import { toPosixPath } from '../../../utils/path';
-import { profileAsync } from '../../esbuild/profiling';
+import { profileAsync, profileSync } from '../../esbuild/profiling';
 import { AngularCompilation, DiagnosticModes } from './angular-compilation';
 import { convertTypeScriptDiagnostic } from './diagnostics';
 
 export abstract class TypeScriptCompilation extends AngularCompilation {
+  static #angularCompilerCliModule?: typeof ng;
+
+  static async loadCompilerCli(): Promise<typeof ng> {
+    TypeScriptCompilation.#angularCompilerCliModule ??= await import('@angular/compiler-cli');
+
+    return TypeScriptCompilation.#angularCompilerCliModule;
+  }
+
+  protected async loadConfiguration(tsconfig: string): Promise<ng.ParsedConfiguration> {
+    const { readConfiguration } = await TypeScriptCompilation.loadCompilerCli();
+
+    return profileSync('NG_READ_CONFIG', () =>
+      readConfiguration(tsconfig, {
+        // Angular specific configuration defaults and overrides to ensure a functioning compilation.
+        suppressOutputPathCheck: true,
+        outDir: undefined,
+        sourceMap: false,
+        declaration: false,
+        declarationMap: false,
+        allowEmptyCodegenFiles: false,
+        annotationsAs: 'decorators',
+        enableResourceInlining: false,
+        supportTestBed: false,
+        supportJitMode: false,
+        // Disable removing of comments as TS is quite aggressive with these and can
+        // remove important annotations, such as /* @__PURE__ */ and comments like /* vite-ignore */.
+        removeComments: false,
+      }),
+    );
+  }
+
   protected readonly sourceFiles = new Map<string, ts.SourceFile>();
 
   protected invalidateFiles(files: Iterable<string>): void {