fix(@angular-devkit/build-angular): automatically include known packa…

…ges in vite prebundling

When using the Vite-based development server, the application build step already contains the
list of known packages that would need to be prebundled. This information can be passed to Vite
directly to avoid Vite needing to perform discovery on every output file that will be requested.
This also avoids the Vite server behavior where Vite forces a reload of the page when it discovers
a new dependency. This behavior can result in lost state during lazy loading of a route.

packages/angular_devkit/build_angular/src/builders/application/execute-build.ts

@@ -168,6 +168,15 @@ export async function executeBuild(
     return executionResult;
   }
 
+  // Analyze external imports if external options are enabled
+  if (options.externalPackages || options.externalDependencies?.length) {
+    // TODO: Filter externalImports to generate second argument to support wildcard externalDependency values
+    executionResult.setExternalMetadata(
+      [...bundlingResult.externalImports],
+      options.externalDependencies,
+    );
+  }
+
   const { metafile, initialFiles, outputFiles } = bundlingResult;
 
   executionResult.outputFiles.push(...outputFiles);

packages/angular_devkit/build_angular/src/builders/dev-server/vite-server.ts

@@ -115,6 +115,10 @@ export async function* serveWithVite(
   let hadError = false;
   const generatedFiles = new Map<string, OutputFileRecord>();
   const assetFiles = new Map<string, string>();
+  const externalMetadata: { implicit: string[]; explicit: string[] } = {
+    implicit: [],
+    explicit: [],
+  };
   const build =
     builderName === '@angular-devkit/build-angular:application'
       ? buildApplicationInternal
@@ -166,6 +170,15 @@ export async function* serveWithVite(
       }
     }
 
+    // To avoid disconnecting the array objects from the option, these arrays need to be mutated
+    // instead of replaced.
+    if (result.externalMetadata.explicit) {
+      externalMetadata.explicit.push(...result.externalMetadata.explicit);
+    }
+    if (result.externalMetadata.implicit) {
+      externalMetadata.implicit.push(...result.externalMetadata.implicit);
+    }
+
     if (server) {
       handleUpdate(generatedFiles, server, serverOptions, context.logger);
     } else {
@@ -185,7 +198,7 @@ export async function* serveWithVite(
         generatedFiles,
         assetFiles,
         browserOptions.preserveSymlinks,
-        browserOptions.externalDependencies,
+        externalMetadata,
         !!browserOptions.ssr,
         prebundleTransformer,
         target,
@@ -336,7 +349,7 @@ export async function setupServer(
   outputFiles: Map<string, OutputFileRecord>,
   assets: Map<string, string>,
   preserveSymlinks: boolean | undefined,
-  prebundleExclude: string[] | undefined,
+  externalMetadata: { implicit: string[]; explicit: string[] },
   ssr: boolean,
   prebundleTransformer: JavaScriptTransformer,
   target: string[],
@@ -381,7 +394,7 @@ export async function setupServer(
     },
     ssr: {
       // Exclude any provided dependencies (currently build defined externals)
-      external: prebundleExclude,
+      external: externalMetadata.implicit,
     },
     plugins: [
       createAngularLocaleDataPlugin(),
@@ -598,8 +611,10 @@ export async function setupServer(
     optimizeDeps: {
       // Only enable with caching since it causes prebundle dependencies to be cached
       disabled: !serverOptions.cacheOptions.enabled,
-      // Exclude any provided dependencies (currently build defined externals)
-      exclude: prebundleExclude,
+      // Exclude any explicitly defined dependencies (currently build defined externals)
+      exclude: externalMetadata.explicit,
+      // Include all implict dependencies from the external packages internal option
+      include: externalMetadata.implicit,
       // Skip automatic file-based entry point discovery
       entries: [],
       // Add an esbuild plugin to run the Angular linker on dependencies

packages/angular_devkit/build_angular/src/tools/esbuild/bundler-context.ts

@@ -29,6 +29,7 @@ export type BundleContextResult =
       metafile: Metafile;
       outputFiles: BuildOutputFile[];
       initialFiles: Map<string, InitialFileRecord>;
+      externalImports: Set<string>;
     };
 
 export interface InitialFileRecord {
@@ -105,6 +106,7 @@ export class BundlerContext {
     const warnings: Message[] = [];
     const metafile: Metafile = { inputs: {}, outputs: {} };
     const initialFiles = new Map<string, InitialFileRecord>();
+    const externalImports = new Set<string>();
     const outputFiles = [];
     for (const result of individualResults) {
       warnings.push(...result.warnings);
@@ -122,6 +124,7 @@ export class BundlerContext {
 
       result.initialFiles.forEach((value, key) => initialFiles.set(key, value));
       outputFiles.push(...result.outputFiles);
+      result.externalImports.forEach((value) => externalImports.add(value));
     }
 
     if (errors !== undefined) {
@@ -134,6 +137,7 @@ export class BundlerContext {
       metafile,
       initialFiles,
       outputFiles,
+      externalImports,
     };
   }
 
@@ -284,6 +288,20 @@ export class BundlerContext {
       }
     }
 
+    // Collect all external package names
+    const externalImports = new Set<string>();
+    for (const { imports } of Object.values(result.metafile.outputs)) {
+      for (const importData of imports) {
+        if (
+          !importData.external ||
+          (importData.kind !== 'import-statement' && importData.kind !== 'dynamic-import')
+        ) {
+          continue;
+        }
+        externalImports.add(importData.path);
+      }
+    }
+
     const outputFiles = result.outputFiles.map((file) => {
       let fileType: BuildOutputFileType;
       if (dirname(file.path) === 'media') {
@@ -303,6 +321,7 @@ export class BundlerContext {
       ...result,
       outputFiles,
       initialFiles,
+      externalImports,
       errors: undefined,
     };
   }

packages/angular_devkit/build_angular/src/tools/esbuild/bundler-execution-result.ts

@@ -30,6 +30,7 @@ export class ExecutionResult {
   outputFiles: BuildOutputFile[] = [];
   assetFiles: BuildOutputAsset[] = [];
   errors: Message[] = [];
+  externalMetadata?: { implicit: string[]; explicit?: string[] };
 
   constructor(
     private rebuildContexts: BundlerContext[],
@@ -48,6 +49,16 @@ export class ExecutionResult {
     this.errors.push(...errors);
   }
 
+  /**
+   * Add external JavaScript import metadata to the result. This is currently used
+   * by the development server to optimize the prebundling process.
+   * @param implicit External dependencies due to the external packages option.
+   * @param explicit External dependencies due to explicit project configuration.
+   */
+  setExternalMetadata(implicit: string[], explicit: string[] | undefined) {
+    this.externalMetadata = { implicit, explicit };
+  }
+
   get output() {
     return {
       success: this.errors.length === 0,
@@ -60,6 +71,7 @@ export class ExecutionResult {
       outputFiles: this.outputFiles,
       assetFiles: this.assetFiles,
       errors: this.errors,
+      externalMetadata: this.externalMetadata,
     };
   }