fix(@angular/ssr): avoid preloading unnecessary dynamic bundles

This change to `@angular/ssr` prevents the preloading of dynamically imported bundles that aren't directly associated with routing.

Previously, Angular SSR might preload all dynamic bundles, even those not immediately required, such as deferred chunks within components.

Closes #30541

Author: alan-agius4

packages/angular/build/src/utils/server-rendering/manifest.ts

@@ -201,34 +201,22 @@ function generateLazyLoadedFilesMappings(
   metafile: Metafile,
   initialFiles: Set<string>,
   publicPath = '',
-): Record<string, FilesMapping[]> {
-  const entryPointToBundles: Record<string, FilesMapping[]> = {};
+): Record<string, string[]> {
+  const entryPointToBundles: Record<string, string[]> = {};
   for (const [fileName, { entryPoint, exports, imports }] of Object.entries(metafile.outputs)) {
     // Skip files that don't have an entryPoint, no exports, or are not .js
     if (!entryPoint || exports?.length < 1 || !fileName.endsWith('.js')) {
       continue;
     }
 
-    const importedPaths: FilesMapping[] = [
-      {
-        path: `${publicPath}${fileName}`,
-        dynamicImport: false,
-      },
-    ];
+    const importedPaths: string[] = [`${publicPath}${fileName}`];
 
     for (const { kind, external, path } of imports) {
-      if (
-        external ||
-        initialFiles.has(path) ||
-        (kind !== 'dynamic-import' && kind !== 'import-statement')
-      ) {
+      if (external || initialFiles.has(path) || kind !== 'import-statement') {
         continue;
       }
 
-      importedPaths.push({
-        path: `${publicPath}${path}`,
-        dynamicImport: kind === 'dynamic-import',
-      });
+      importedPaths.push(`${publicPath}${path}`);
     }
 
     entryPointToBundles[entryPoint] = importedPaths;

packages/angular/ssr/src/manifest.ts

@@ -123,21 +123,16 @@ export interface AngularAppManifest {
    * Maps entry-point names to their corresponding browser bundles and loading strategies.
    *
    * - **Key**: The entry-point name, typically the value of `ɵentryName`.
-   * - **Value**: An array of objects, each representing a browser bundle with:
-   *   - `path`: The filename or URL of the associated JavaScript bundle to preload.
-   *   - `dynamicImport`: A boolean indicating whether the bundle is loaded via a dynamic `import()`.
-   *     If `true`, the bundle is lazily loaded, impacting its preloading behavior.
+   * - **Value**: A readonly array of JavaScript bundle paths or `undefined` if no bundles are associated.
    *
    * ### Example
    * ```ts
    * {
-   *   'src/app/lazy/lazy.ts': [{ path: 'src/app/lazy/lazy.js', dynamicImport: true }]
+   *   'src/app/lazy/lazy.ts': ['src/app/lazy/lazy.js']
    * }
    * ```
    */
-  readonly entryPointToBrowserMapping?: Readonly<
-    Record<string, ReadonlyArray<{ path: string; dynamicImport: boolean }> | undefined>
-  >;
+  readonly entryPointToBrowserMapping?: Readonly<Record<string, readonly string[] | undefined>>;
 }
 
 /**

packages/angular/ssr/src/routes/ng-routes.ts

@@ -148,7 +148,7 @@ async function* handleRoute(options: {
 
     const { redirectTo, loadChildren, loadComponent, children, ɵentryName } = route;
     if (ɵentryName && loadComponent) {
-      appendPreloadToMetadata(ɵentryName, entryPointToBrowserMapping, metadata, true);
+      appendPreloadToMetadata(ɵentryName, entryPointToBrowserMapping, metadata);
     }
 
     if (metadata.renderMode === RenderMode.Prerender) {
@@ -192,11 +192,7 @@ async function* handleRoute(options: {
     // Load and process lazy-loaded child routes
     if (loadChildren) {
       if (ɵentryName) {
-        // When using `loadChildren`, the entire feature area (including multiple routes) is loaded.
-        // As a result, we do not want all dynamic-import dependencies to be preload, because it involves multiple dependencies
-        // across different child routes. In contrast, `loadComponent` only loads a single component, which allows
-        // for precise control over preloading, ensuring that the files preloaded are exactly those required for that specific route.
-        appendPreloadToMetadata(ɵentryName, entryPointToBrowserMapping, metadata, false);
+        appendPreloadToMetadata(ɵentryName, entryPointToBrowserMapping, metadata);
       }
 
       const loadedChildRoutes = await loadChildrenHelper(
@@ -336,7 +332,6 @@ function appendPreloadToMetadata(
   entryName: string,
   entryPointToBrowserMapping: EntryPointToBrowserMapping,
   metadata: ServerConfigRouteTreeNodeMetadata,
-  includeDynamicImports: boolean,
 ): void {
   const existingPreloads = metadata.preload ?? [];
   if (!entryPointToBrowserMapping || existingPreloads.length >= MODULE_PRELOAD_MAX) {
@@ -350,13 +345,8 @@ function appendPreloadToMetadata(
 
   // Merge existing preloads with new ones, ensuring uniqueness and limiting the total to the maximum allowed.
   const combinedPreloads: Set<string> = new Set(existingPreloads);
-  for (const { dynamicImport, path } of preload) {
-    if (dynamicImport && !includeDynamicImports) {
-      continue;
-    }
-
-    combinedPreloads.add(path);
-
+  for (const href of preload) {
+    combinedPreloads.add(href);
     if (combinedPreloads.size === MODULE_PRELOAD_MAX) {
       break;
     }

tests/legacy-cli/e2e/tests/build/server-rendering/server-routes-preload-links.ts

@@ -143,17 +143,15 @@ const RESPONSE_EXPECTS: Record<
     matches: [
       /<link rel="modulepreload" href="(ssg\.routes-[a-zA-Z0-9]{8}\.js)">/,
       /<link rel="modulepreload" href="(ssg-one-[a-zA-Z0-9]{8}\.js)">/,
-      /<link rel="modulepreload" href="(cross-dep-[a-zA-Z0-9]{8}\.js)">/,
     ],
-    notMatches: [/home/, /ssr/, /csr/, /ssg-two/, /ssg\-component/],
+    notMatches: [/home/, /ssr/, /csr/, /ssg-two/, /ssg\-component/, /cross-dep-/],
   },
   '/ssg/two': {
     matches: [
       /<link rel="modulepreload" href="(ssg\.routes-[a-zA-Z0-9]{8}\.js)">/,
       /<link rel="modulepreload" href="(ssg-two-[a-zA-Z0-9]{8}\.js)">/,
-      /<link rel="modulepreload" href="(cross-dep-[a-zA-Z0-9]{8}\.js)">/,
     ],
-    notMatches: [/home/, /ssr/, /csr/, /ssg-one/, /ssg\-component/],
+    notMatches: [/home/, /ssr/, /csr/, /ssg-one/, /ssg\-component/, /cross-dep-/],
   },
   '/ssr': {
     matches: [/<link rel="modulepreload" href="(ssr-[a-zA-Z0-9]{8}\.js)">/],