refactor(@angular/build): unify configuration loading and option transformations in TypeScriptCompilation

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

@@ -8,7 +8,7 @@
 
 import ts from 'typescript';
 import type { AngularHostOptions } from '../angular-host';
-import { transformCompilerOptions } from './compiler-options';
+import { CompilerOptionOverrides, transformCompilerOptions } from './compiler-options';
 import { TypeScriptCompilation } from './typescript-compilation';
 import {
   AngularCompilation,
@@ -90,6 +90,10 @@ describe('AngularCompilation', () => {
       public getCachedSourceFiles(): Map<string, ts.SourceFile> {
         return this.sourceFiles;
       }
+
+      public async testLoadConfiguration(tsconfig: string, overrides?: CompilerOptionOverrides) {
+        return this.loadConfiguration(tsconfig, overrides);
+      }
     }
 
     it('collects and converts diagnostics categorized by error and warning', async () => {
@@ -134,6 +138,32 @@ describe('AngularCompilation', () => {
       expect(compilerCli).toBeDefined();
       expect(typeof compilerCli.readConfiguration).toBe('function');
     });
+
+    it('loads configuration and applies compiler option transformations', async () => {
+      const compilation = new MockTypeScriptCompilation();
+      const mockReadConfig = jasmine.createSpy('readConfiguration').and.returnValue({
+        options: { target: ts.ScriptTarget.ES2020 },
+        rootNames: ['/src/main.ts'],
+        errors: [],
+      });
+      spyOn(TypeScriptCompilation, 'loadCompilerCli').and.resolveTo({
+        readConfiguration: mockReadConfig,
+      } as unknown as typeof import('@angular/compiler-cli'));
+
+      const result = await compilation.testLoadConfiguration('tsconfig.json', { sourcemap: true });
+
+      expect(mockReadConfig).toHaveBeenCalledWith(
+        'tsconfig.json',
+        jasmine.objectContaining({
+          suppressOutputPathCheck: true,
+          outDir: undefined,
+        }),
+      );
+      expect(result.rootNames).toEqual(['/src/main.ts']);
+      expect(result.compilerOptions.target).toBe(ts.ScriptTarget.ES2022);
+      expect(result.compilerOptions.inlineSources).toBe(true);
+      expect(result.warnings.length).toBeGreaterThan(0);
+    });
   });
 
   describe('createAngularCompilation', () => {

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

@@ -7,7 +7,6 @@
  */
 
 import type * as ng from '@angular/compiler-cli';
-import type { PartialMessage } from 'esbuild';
 import assert from 'node:assert';
 import { relative } from 'node:path';
 import ts from 'typescript';
@@ -26,7 +25,7 @@ import {
   DiagnosticModes,
   type EmitFileResult,
 } from './angular-compilation';
-import { CompilerOptionOverrides, transformCompilerOptions } from './compiler-options';
+import type { CompilerOptionOverrides } from './compiler-options';
 import { collectHmrCandidates } from './hmr-candidates';
 import { TypeScriptCompilation } from './typescript-compilation';
 import { printSourceFileWithMap } from './typescript-printer';
@@ -72,17 +71,11 @@ export class AotCompilation extends TypeScriptCompilation {
 
     // Load the compiler configuration and transform as needed
     const {
-      options: originalCompilerOptions,
+      compilerOptions,
       rootNames,
       errors: configurationDiagnostics,
-    } = await this.loadConfiguration(tsconfig);
-
-    const { compilerOptions, warnings } = transformCompilerOptions(
-      ts,
-      originalCompilerOptions,
-      compilerOptionOverrides,
-      tsconfig,
-    );
+      warnings,
+    } = await this.loadConfiguration(tsconfig, compilerOptionOverrides);
 
     const useTypeScriptTranspilation =
       (compilerOptions['_useTypeScriptTranspilation'] as boolean | undefined) ??

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

@@ -7,7 +7,6 @@
  */
 
 import type * as ng from '@angular/compiler-cli';
-import type { PartialMessage } from 'esbuild';
 import assert from 'node:assert';
 import ts from 'typescript';
 import { profileSync } from '../../esbuild/profiling';
@@ -20,7 +19,7 @@ import {
   DiagnosticModes,
   type EmitFileResult,
 } from './angular-compilation';
-import { CompilerOptionOverrides, transformCompilerOptions } from './compiler-options';
+import type { CompilerOptionOverrides } from './compiler-options';
 import { TypeScriptCompilation } from './typescript-compilation';
 
 class JitCompilationState {
@@ -51,17 +50,11 @@ export class JitCompilation extends TypeScriptCompilation {
 
     // Load the compiler configuration and transform as needed
     const {
-      options: originalCompilerOptions,
+      compilerOptions,
       rootNames,
       errors: configurationDiagnostics,
-    } = await this.loadConfiguration(tsconfig);
-
-    const { compilerOptions, warnings } = transformCompilerOptions(
-      ts,
-      originalCompilerOptions,
-      compilerOptionOverrides,
-      tsconfig,
-    );
+      warnings,
+    } = await this.loadConfiguration(tsconfig, compilerOptionOverrides);
 
     if (hostOptions.modifiedFiles) {
       this.invalidateFiles(hostOptions.modifiedFiles);

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

@@ -12,8 +12,16 @@ import ts from 'typescript';
 import { toPosixPath } from '../../../utils/path';
 import { profileAsync, profileSync } from '../../esbuild/profiling';
 import { AngularCompilation, DiagnosticModes } from './angular-compilation';
+import { type CompilerOptionOverrides, transformCompilerOptions } from './compiler-options';
 import { convertTypeScriptDiagnostic } from './diagnostics';
 
+export interface TransformedConfiguration {
+  compilerOptions: ng.CompilerOptions;
+  rootNames: string[];
+  errors: ts.Diagnostic[];
+  warnings: PartialMessage[];
+}
+
 export abstract class TypeScriptCompilation extends AngularCompilation {
   static #angularCompilerCliModule?: typeof ng;
 
@@ -23,10 +31,17 @@ export abstract class TypeScriptCompilation extends AngularCompilation {
     return TypeScriptCompilation.#angularCompilerCliModule;
   }
 
-  protected async loadConfiguration(tsconfig: string): Promise<ng.ParsedConfiguration> {
+  protected async loadConfiguration(
+    tsconfig: string,
+    compilerOptionOverrides?: CompilerOptionOverrides,
+  ): Promise<TransformedConfiguration> {
     const { readConfiguration } = await TypeScriptCompilation.loadCompilerCli();
 
-    return profileSync('NG_READ_CONFIG', () =>
+    const {
+      options: originalCompilerOptions,
+      rootNames,
+      errors,
+    } = profileSync('NG_READ_CONFIG', () =>
       readConfiguration(tsconfig, {
         // Angular specific configuration defaults and overrides to ensure a functioning compilation.
         suppressOutputPathCheck: true,
@@ -44,6 +59,20 @@ export abstract class TypeScriptCompilation extends AngularCompilation {
         removeComments: false,
       }),
     );
+
+    const { compilerOptions, warnings } = transformCompilerOptions(
+      ts,
+      originalCompilerOptions,
+      compilerOptionOverrides,
+      tsconfig,
+    );
+
+    return {
+      compilerOptions,
+      rootNames,
+      errors,
+      warnings,
+    };
   }
 
   protected readonly sourceFiles = new Map<string, ts.SourceFile>();