perf(@angular/build): reuse TS package.json cache when rebuilding

TypeScript 5.6 and higher added functionality that will search for a `package.json` file for source files that are part of the program (e.g., `.d.ts`) and within a node modules directory. This can be an expensive tasks especially considering the large amount of `.d.ts` files within packages. TypeScript supports using a cache of known `package.json` files to improve the performance of this task. The Angular CLI will now provide and reuse this cache across rebuilds during watch mode. This includes the use of `ng serve`. The performance difference is most apparent for the Angular template diagnostic step of the build. Internally the Angular compiler creates a new template typechecking program which causes the `package.json` search process to occur. By leveraging the cache, this process becomes a series of cache hits. In the event that files are modified within the node modules directory, the cache is invalidated and the following rebuild may be longer as a result.
angular · Dec 5, 2024 · 75998eb · 75998eb
1 parent 15a48a3
commit 75998eb
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Showing 3 changed files with 32 additions and 16 deletions.
diff --git a/packages/angular/build/src/tools/angular/angular-host.ts b/packages/angular/build/src/tools/angular/angular-host.ts
@@ -164,6 +164,7 @@ export function createAngularCompilerHost(
   typescript: typeof ts,
   compilerOptions: AngularCompilerOptions,
   hostOptions: AngularHostOptions,
+  packageJsonCache: ts.PackageJsonInfoCache | undefined,
 ): AngularCompilerHost {
   // Create TypeScript compiler host
   const host: AngularCompilerHost = typescript.createIncrementalCompilerHost(compilerOptions);
@@ -229,16 +230,17 @@ export function createAngularCompilerHost(
     return hostOptions.modifiedFiles;
   };
 
+  // Provide a resolution cache to ensure package.json lookups are cached
+  const resolutionCache = typescript.createModuleResolutionCache(
+    host.getCurrentDirectory(),
+    host.getCanonicalFileName.bind(host),
+    compilerOptions,
+    packageJsonCache,
+  );
+  host.getModuleResolutionCache = () => resolutionCache;
+
   // Augment TypeScript Host for file replacements option
   if (hostOptions.fileReplacements) {
-    // Provide a resolution cache since overriding resolution prevents automatic creation
-    const resolutionCache = typescript.createModuleResolutionCache(
-      host.getCurrentDirectory(),
-      host.getCanonicalFileName.bind(host),
-      compilerOptions,
-    );
-    host.getModuleResolutionCache = () => resolutionCache;
-
     augmentHostWithReplacements(typescript, host, hostOptions.fileReplacements, resolutionCache);
   }
 

diff --git a/packages/angular/build/src/tools/angular/compilation/aot-compilation.ts b/packages/angular/build/src/tools/angular/compilation/aot-compilation.ts
@@ -74,25 +74,39 @@ export class AotCompilation extends AngularCompilation {
       hostOptions.externalStylesheets ??= new Map();
     }
 
+    // Reuse the package.json cache from the previous compilation
+    const packageJsonCache = this.#state?.compilerHost
+      .getModuleResolutionCache?.()
+      ?.getPackageJsonInfoCache();
+
     const useHmr =
       compilerOptions['_enableHmr'] &&
       hostOptions.modifiedFiles &&
       hostOptions.modifiedFiles.size <= HMR_MODIFIED_FILE_LIMIT;
 
-    // Collect stale source files for HMR analysis of inline component resources
     let staleSourceFiles;
-    if (useHmr && hostOptions.modifiedFiles && this.#state) {
+    let clearPackageJsonCache = false;
+    if (hostOptions.modifiedFiles && this.#state) {
       for (const modifiedFile of hostOptions.modifiedFiles) {
-        const sourceFile = this.#state.typeScriptProgram.getSourceFile(modifiedFile);
-        if (sourceFile) {
-          staleSourceFiles ??= new Map<string, ts.SourceFile>();
-          staleSourceFiles.set(modifiedFile, sourceFile);
+        // Clear package.json cache if a node modules file was modified
+        if (!clearPackageJsonCache && modifiedFile.includes('node_modules')) {
+          clearPackageJsonCache = true;
+          packageJsonCache?.clear();
+        }
+
+        // Collect stale source files for HMR analysis of inline component resources
+        if (useHmr) {
+          const sourceFile = this.#state.typeScriptProgram.getSourceFile(modifiedFile);
+          if (sourceFile) {
+            staleSourceFiles ??= new Map<string, ts.SourceFile>();
+            staleSourceFiles.set(modifiedFile, sourceFile);
+          }
         }
       }
     }
 
     // Create Angular compiler host
-    const host = createAngularCompilerHost(ts, compilerOptions, hostOptions);
+    const host = createAngularCompilerHost(ts, compilerOptions, hostOptions, packageJsonCache);
 
     // Create the Angular specific program that contains the Angular compiler
     const angularProgram = profileSync(

diff --git a/packages/angular/build/src/tools/angular/compilation/jit-compilation.ts b/packages/angular/build/src/tools/angular/compilation/jit-compilation.ts
@@ -53,7 +53,7 @@ export class JitCompilation extends AngularCompilation {
       compilerOptionsTransformer?.(originalCompilerOptions) ?? originalCompilerOptions;
 
     // Create Angular compiler host
-    const host = createAngularCompilerHost(ts, compilerOptions, hostOptions);
+    const host = createAngularCompilerHost(ts, compilerOptions, hostOptions, undefined);
 
     // Create the TypeScript Program
     const typeScriptProgram = profileSync('TS_CREATE_PROGRAM', () =>