perf(@angular-devkit/build-angular): cache Sass in memory with esbuil…

…d watch mode

To improve rebuild performance when using Sass stylesheets with the esbuild-based
browser application builder in watch mode, Sass stylesheets that are not affected
by any file changes will now be cached and directly reused. This avoids performing
potentially expensive Sass preprocessing on stylesheets that will not change within
a rebuild.

(cherry picked from commit 1e78cf9)

packages/angular_devkit/build_angular/src/builders/browser-esbuild/angular/compiler-plugin.ts

@@ -22,6 +22,7 @@ import { pathToFileURL } from 'node:url';
 import ts from 'typescript';
 import { maxWorkers } from '../../../utils/environment-options';
 import { JavaScriptTransformer } from '../javascript-transformer';
+import { LoadResultCache, MemoryLoadResultCache } from '../load-result-cache';
 import {
   logCumulativeDurations,
   profileAsync,
@@ -124,12 +125,14 @@ export class SourceFileCache extends Map<string, ts.SourceFile> {
   readonly modifiedFiles = new Set<string>();
   readonly babelFileCache = new Map<string, Uint8Array>();
   readonly typeScriptFileCache = new Map<string, Uint8Array>();
+  readonly loadResultCache = new MemoryLoadResultCache();
 
   invalidate(files: Iterable<string>): void {
     this.modifiedFiles.clear();
     for (let file of files) {
       this.babelFileCache.delete(file);
       this.typeScriptFileCache.delete(pathToFileURL(file).href);
+      this.loadResultCache.invalidate(file);
 
       // Normalize separators to allow matching TypeScript Host paths
       if (USING_WINDOWS) {
@@ -150,6 +153,7 @@ export interface CompilerPluginOptions {
   thirdPartySourcemaps?: boolean;
   fileReplacements?: Record<string, string>;
   sourceFileCache?: SourceFileCache;
+  loadResultCache?: LoadResultCache;
 }
 
 // eslint-disable-next-line max-lines-per-function
@@ -272,6 +276,7 @@ export function createCompilerPlugin(
               filename,
               !stylesheetFile,
               styleOptions,
+              pluginOptions.loadResultCache,
             );
 
             const { contents, resourceFiles, errors, warnings } = stylesheetResult;
@@ -415,7 +420,12 @@ export function createCompilerPlugin(
 
       // Setup bundling of component templates and stylesheets when in JIT mode
       if (pluginOptions.jit) {
-        setupJitPluginCallbacks(build, styleOptions, stylesheetResourceFiles);
+        setupJitPluginCallbacks(
+          build,
+          styleOptions,
+          stylesheetResourceFiles,
+          pluginOptions.loadResultCache,
+        );
       }
 
       build.onEnd((result) => {

packages/angular_devkit/build_angular/src/builders/browser-esbuild/angular/jit-plugin-callbacks.ts

@@ -9,6 +9,7 @@
 import type { OutputFile, PluginBuild } from 'esbuild';
 import { readFile } from 'node:fs/promises';
 import path from 'node:path';
+import { LoadResultCache } from '../load-result-cache';
 import { BundleStylesheetOptions, bundleComponentStylesheet } from '../stylesheets';
 import {
   JIT_NAMESPACE_REGEXP,
@@ -65,6 +66,7 @@ export function setupJitPluginCallbacks(
   build: PluginBuild,
   styleOptions: BundleStylesheetOptions & { inlineStyleLanguage: string },
   stylesheetResourceFiles: OutputFile[],
+  cache?: LoadResultCache,
 ): void {
   const root = build.initialOptions.absWorkingDir ?? '';
 
@@ -110,6 +112,7 @@ export function setupJitPluginCallbacks(
       entry.path,
       entry.contents !== undefined,
       styleOptions,
+      cache,
     );
 
     stylesheetResourceFiles.push(...resourceFiles);

packages/angular_devkit/build_angular/src/builders/browser-esbuild/index.ts

@@ -27,6 +27,7 @@ import { BundlerContext, logMessages } from './esbuild';
 import { logExperimentalWarnings } from './experimental-warnings';
 import { createGlobalScriptsBundleOptions } from './global-scripts';
 import { extractLicenses } from './license-extractor';
+import { LoadResultCache } from './load-result-cache';
 import { NormalizedBrowserOptions, normalizeOptions } from './options';
 import { shutdownSassWorkerPool } from './sass-plugin';
 import { Schema as BrowserBuilderOptions } from './schema';
@@ -122,7 +123,7 @@ async function execute(
     new BundlerContext(
       workspaceRoot,
       !!options.watch,
-      createGlobalStylesBundleOptions(options, target, browsers),
+      createGlobalStylesBundleOptions(options, target, browsers, codeBundleCache?.loadResultCache),
     );
 
   const globalScriptsBundleContext = new BundlerContext(
@@ -390,6 +391,7 @@ function createCodeBundleOptions(
           advancedOptimizations,
           fileReplacements,
           sourceFileCache,
+          loadResultCache: sourceFileCache?.loadResultCache,
         },
         // Component stylesheet options
         {
@@ -508,6 +510,7 @@ function createGlobalStylesBundleOptions(
   options: NormalizedBrowserOptions,
   target: string[],
   browsers: string[],
+  cache?: LoadResultCache,
 ): BuildOptions {
   const {
     workspaceRoot,
@@ -521,18 +524,21 @@ function createGlobalStylesBundleOptions(
     tailwindConfiguration,
   } = options;
 
-  const buildOptions = createStylesheetBundleOptions({
-    workspaceRoot,
-    optimization: !!optimizationOptions.styles.minify,
-    sourcemap: !!sourcemapOptions.styles,
-    preserveSymlinks,
-    target,
-    externalDependencies,
-    outputNames,
-    includePaths: stylePreprocessorOptions?.includePaths,
-    browsers,
-    tailwindConfiguration,
-  });
+  const buildOptions = createStylesheetBundleOptions(
+    {
+      workspaceRoot,
+      optimization: !!optimizationOptions.styles.minify,
+      sourcemap: !!sourcemapOptions.styles,
+      preserveSymlinks,
+      target,
+      externalDependencies,
+      outputNames,
+      includePaths: stylePreprocessorOptions?.includePaths,
+      browsers,
+      tailwindConfiguration,
+    },
+    cache,
+  );
   buildOptions.legalComments = options.extractLicenses ? 'none' : 'eof';
 
   const namespace = 'angular:styles/global';

packages/angular_devkit/build_angular/src/builders/browser-esbuild/load-result-cache.ts

@@ -0,0 +1,51 @@
+/**
+ * @license
+ * Copyright Google LLC All Rights Reserved.
+ *
+ * Use of this source code is governed by an MIT-style license that can be
+ * found in the LICENSE file at https://angular.io/license
+ */
+
+import type { OnLoadResult } from 'esbuild';
+
+export interface LoadResultCache {
+  get(path: string): OnLoadResult | undefined;
+  put(path: string, result: OnLoadResult): Promise<void>;
+}
+
+export class MemoryLoadResultCache implements LoadResultCache {
+  #loadResults = new Map<string, OnLoadResult>();
+  #fileDependencies = new Map<string, Set<string>>();
+
+  get(path: string): OnLoadResult | undefined {
+    return this.#loadResults.get(path);
+  }
+
+  async put(path: string, result: OnLoadResult): Promise<void> {
+    this.#loadResults.set(path, result);
+    if (result.watchFiles) {
+      for (const watchFile of result.watchFiles) {
+        let affected = this.#fileDependencies.get(watchFile);
+        if (affected === undefined) {
+          affected = new Set();
+          this.#fileDependencies.set(watchFile, affected);
+        }
+        affected.add(path);
+      }
+    }
+  }
+
+  invalidate(path: string): boolean {
+    const affected = this.#fileDependencies.get(path);
+    let found = false;
+
+    if (affected) {
+      affected.forEach((a) => (found ||= this.#loadResults.delete(a)));
+      this.#fileDependencies.delete(path);
+    }
+
+    found ||= this.#loadResults.delete(path);
+
+    return found;
+  }
+}

packages/angular_devkit/build_angular/src/builders/browser-esbuild/sass-plugin.ts

@@ -16,6 +16,7 @@ import type {
   FileImporterWithRequestContextOptions,
   SassWorkerImplementation,
 } from '../../sass/sass-service';
+import type { LoadResultCache } from './load-result-cache';
 
 export interface SassPluginOptions {
   sourcemap: boolean;
@@ -34,7 +35,7 @@ export function shutdownSassWorkerPool(): void {
   sassWorkerPool = undefined;
 }
 
-export function createSassPlugin(options: SassPluginOptions): Plugin {
+export function createSassPlugin(options: SassPluginOptions, cache?: LoadResultCache): Plugin {
   return {
     name: 'angular-sass',
     setup(build: PluginBuild): void {
@@ -69,17 +70,35 @@ export function createSassPlugin(options: SassPluginOptions): Plugin {
           `component style name should always be found [${args.path}]`,
         );
 
-        const [language, , filePath] = args.path.split(';', 3);
-        const syntax = language === 'sass' ? 'indented' : 'scss';
+        let result = cache?.get(data);
+        if (result === undefined) {
+          const [language, , filePath] = args.path.split(';', 3);
+          const syntax = language === 'sass' ? 'indented' : 'scss';
 
-        return compileString(data, filePath, syntax, options, resolveUrl);
+          result = await compileString(data, filePath, syntax, options, resolveUrl);
+          if (result.errors === undefined) {
+            // Cache the result if there were no errors
+            await cache?.put(data, result);
+          }
+        }
+
+        return result;
       });
 
       build.onLoad({ filter: /\.s[ac]ss$/ }, async (args) => {
-        const data = await readFile(args.path, 'utf-8');
-        const syntax = extname(args.path).toLowerCase() === '.sass' ? 'indented' : 'scss';
+        let result = cache?.get(args.path);
+        if (result === undefined) {
+          const data = await readFile(args.path, 'utf-8');
+          const syntax = extname(args.path).toLowerCase() === '.sass' ? 'indented' : 'scss';
+
+          result = await compileString(data, args.path, syntax, options, resolveUrl);
+          if (result.errors === undefined) {
+            // Cache the result if there were no errors
+            await cache?.put(args.path, result);
+          }
+        }
 
-        return compileString(data, args.path, syntax, options, resolveUrl);
+        return result;
       });
     },
   };

packages/angular_devkit/build_angular/src/builders/browser-esbuild/stylesheets.ts

@@ -12,6 +12,7 @@ import { createCssPlugin } from './css-plugin';
 import { createCssResourcePlugin } from './css-resource-plugin';
 import { BundlerContext } from './esbuild';
 import { createLessPlugin } from './less-plugin';
+import { LoadResultCache } from './load-result-cache';
 import { createSassPlugin } from './sass-plugin';
 
 /**
@@ -34,6 +35,7 @@ export interface BundleStylesheetOptions {
 
 export function createStylesheetBundleOptions(
   options: BundleStylesheetOptions,
+  cache?: LoadResultCache,
   inlineComponentData?: Record<string, string>,
 ): BuildOptions & { plugins: NonNullable<BuildOptions['plugins']> } {
   // Ensure preprocessor include paths are absolute based on the workspace root
@@ -59,11 +61,14 @@ export function createStylesheetBundleOptions(
     conditions: ['style', 'sass'],
     mainFields: ['style', 'sass'],
     plugins: [
-      createSassPlugin({
-        sourcemap: !!options.sourcemap,
-        loadPaths: includePaths,
-        inlineComponentData,
-      }),
+      createSassPlugin(
+        {
+          sourcemap: !!options.sourcemap,
+          loadPaths: includePaths,
+          inlineComponentData,
+        },
+        cache,
+      ),
       createLessPlugin({
         sourcemap: !!options.sourcemap,
         includePaths,
@@ -100,11 +105,12 @@ export async function bundleComponentStylesheet(
   filename: string,
   inline: boolean,
   options: BundleStylesheetOptions,
+  cache?: LoadResultCache,
 ) {
   const namespace = 'angular:styles/component';
   const entry = [language, componentStyleCounter++, filename].join(';');
 
-  const buildOptions = createStylesheetBundleOptions(options, { [entry]: data });
+  const buildOptions = createStylesheetBundleOptions(options, cache, { [entry]: data });
   buildOptions.entryPoints = [`${namespace};${entry}`];
   buildOptions.plugins.push({
     name: 'angular-component-styles',