fixup! perf(@angular/build): cache transformed configuration in TypeS…

…cript compilation
alan-agius4 · Sep 28, 2026 · Sep 29, 2026 · Sep 30, 2026 · Sep 30, 2026 · Oct 1, 2026
commit 6c1e983ddf90a8d5f395ecf3a9d1a04c543e099e
diff --git a/packages/angular/build/src/tools/angular/compilation/angular-compilation_spec.ts b/packages/angular/build/src/tools/angular/compilation/angular-compilation_spec.ts
@@ -165,6 +165,41 @@ describe('AngularCompilation', () => {
       expect(result.compilerOptions.target).toBe(ts.ScriptTarget.ES2022);
       expect(result.compilerOptions.inlineSources).toBe(true);
       expect(result.warnings.length).toBeGreaterThan(0);
+      expect(result.tsConfigFiles).toEqual(['tsconfig.json']);
+    });
+
+    it('caches transformed configuration when rootFiles are provided and invalidates on config change', 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 overrides: CompilerOptionOverrides = { rootFiles: ['/src/main.ts'] };
+
+      const result1 = await compilation.testLoadConfiguration('tsconfig.json', overrides);
+      expect(mockReadConfig).toHaveBeenCalledTimes(1);
+
+      // Re-loading with same rootFiles should return cached configuration without calling readConfiguration
+      const result2 = await compilation.testLoadConfiguration('tsconfig.json', overrides);
+      expect(mockReadConfig).toHaveBeenCalledTimes(1);
+      expect(result2).toBe(result1);
+
+      // Invalidation of non-config file should keep cache intact
+      await compilation.update?.(new Set(['/src/main.ts']));
+      const result3 = await compilation.testLoadConfiguration('tsconfig.json', overrides);
+      expect(mockReadConfig).toHaveBeenCalledTimes(1);
+      expect(result3).toBe(result1);
+
+      // Invalidation of tsconfig file should clear cache
+      await compilation.update?.(new Set(['tsconfig.json']));
+      const result4 = await compilation.testLoadConfiguration('tsconfig.json', overrides);
+      expect(mockReadConfig).toHaveBeenCalledTimes(2);
+      expect(result4).toBeDefined();
     });
   });
 

diff --git a/packages/angular/build/src/tools/angular/compilation/aot-compilation.ts b/packages/angular/build/src/tools/angular/compilation/aot-compilation.ts
@@ -77,7 +77,7 @@ export class AotCompilation extends TypeScriptCompilation {
       rootNames,
       errors: configurationDiagnostics,
       warnings,
-      extendedConfigFiles,
+      tsConfigFiles,
     } = await this.loadConfiguration(tsconfig, compilerOptionOverrides, buildType);
 
     const useTypeScriptTranspilation =
@@ -211,7 +211,7 @@ export class AotCompilation extends TypeScriptCompilation {
 
     // Get all files referenced in the TypeScript/Angular program including component resources
     const referencedFiles = [
-      ...(extendedConfigFiles ?? []),
+      ...tsConfigFiles,
       ...typeScriptProgram
         .getSourceFiles()
         .filter((sourceFile) => !angularCompiler.ignoreForEmit.has(sourceFile))

diff --git a/packages/angular/build/src/tools/angular/compilation/jit-compilation.ts b/packages/angular/build/src/tools/angular/compilation/jit-compilation.ts
@@ -55,7 +55,7 @@ export class JitCompilation extends TypeScriptCompilation {
       rootNames,
       errors: configurationDiagnostics,
       warnings,
-      extendedConfigFiles,
+      tsConfigFiles,
     } = await this.loadConfiguration(tsconfig, compilerOptionOverrides, buildType);
 
     if (hostOptions.modifiedFiles) {
@@ -91,7 +91,7 @@ export class JitCompilation extends TypeScriptCompilation {
     );
 
     const referencedFiles = [
-      ...(extendedConfigFiles ?? []),
+      ...tsConfigFiles,
       ...typeScriptProgram.getSourceFiles().map((sourceFile) => sourceFile.fileName),
     ];
 

diff --git a/packages/angular/build/src/tools/angular/compilation/typescript-compilation.ts b/packages/angular/build/src/tools/angular/compilation/typescript-compilation.ts
@@ -20,13 +20,14 @@ export interface TransformedConfiguration {
   rootNames: string[];
   errors: ts.Diagnostic[];
   warnings: PartialMessage[];
-  extendedConfigFiles?: readonly string[];
+  tsConfigFiles: readonly string[];
 }
 
 export abstract class TypeScriptCompilation extends AngularCompilation {
   static #angularCompilerCliModule?: typeof ng;
   #cachedConfiguration?: TransformedConfiguration;
   #cachedRootFiles?: readonly string[];
+  #tsConfigFiles?: Set<string>;
   readonly #extendedConfigCache = new Map<string, ts.ExtendedConfigCacheEntry>();
 
   static async loadCompilerCli(): Promise<typeof ng> {
@@ -91,6 +92,8 @@ export abstract class TypeScriptCompilation extends AngularCompilation {
       ),
     );
 
+    this.#tsConfigFiles = new Set([toPosixPath(tsconfig), ...this.#extendedConfigCache.keys()]);
+
     let rootNames = originalRootNames;
     if (compilerOptionOverrides?.rootFiles?.length) {
       const rootFilesSet = new Set(
@@ -117,10 +120,10 @@ export abstract class TypeScriptCompilation extends AngularCompilation {
       rootNames,
       errors,
       warnings,
-      extendedConfigFiles: [...this.#extendedConfigCache.keys()],
+      tsConfigFiles: Array.from(this.#tsConfigFiles),
     };
 
-    if (config.extendedConfigFiles?.length && currentRootFiles?.length) {
+    if (currentRootFiles?.length) {
       this.#cachedConfiguration = config;
       this.#cachedRootFiles = currentRootFiles;
     }
@@ -131,34 +134,36 @@ export abstract class TypeScriptCompilation extends AngularCompilation {
   protected readonly sourceFiles = new Map<string, ts.SourceFile>();
 
   protected invalidateFiles(files: Iterable<string>): void {
+    const tsConfigFiles = this.#tsConfigFiles;
+
     for (const file of files) {
       const posixFile = toPosixPath(file);
       this.sourceFiles.delete(posixFile);
 
-      if (!this.#extendedConfigCache.size) {
+      if (!tsConfigFiles) {
         continue;
       }
 
-      let cacheKey: string | undefined;
-      if (this.#extendedConfigCache.has(posixFile)) {
-        cacheKey = posixFile;
+      let tsConfigCachedPath: string | undefined;
+      if (tsConfigFiles.has(posixFile)) {
+        tsConfigCachedPath = posixFile;
       } else {
         // Check with lowercased key because TypeScript lowercases the keys
         // of the extended config cache on case-insensitive operating systems.
         const lowerCasedPosixFile = posixFile.toLowerCase();
-        if (this.#extendedConfigCache.has(lowerCasedPosixFile)) {
-          cacheKey = lowerCasedPosixFile;
+        if (tsConfigFiles.has(lowerCasedPosixFile)) {
+          tsConfigCachedPath = lowerCasedPosixFile;
         }
       }
 
-      if (!cacheKey) {
+      if (!tsConfigCachedPath) {
         continue;
       }
 
       // If a tsconfig changes, we need to re-read the configuration.
       this.#cachedConfiguration = undefined;
       this.#cachedRootFiles = undefined;
-      this.#extendedConfigCache.delete(cacheKey);
+      this.#extendedConfigCache.delete(tsConfigCachedPath);
     }
   }