feat(@angular/build): support middlewareConfig

packages/angular/build/src/builders/dev-server/options.ts

@@ -115,6 +115,7 @@ export async function normalizeOptions(
     sslKey,
     prebundle,
     allowedHosts,
+    middlewareConfig,
   } = options;
 
   // Return all the normalized options
@@ -142,5 +143,6 @@ export async function normalizeOptions(
     prebundle: cacheOptions.enabled && !optimization.scripts && prebundle,
     inspect,
     allowedHosts: allowedHosts ? allowedHosts : [],
+    middlewareConfig,
   };
 }

packages/angular/build/src/builders/dev-server/schema.json

@@ -110,29 +110,43 @@
           "type": "string",
           "description": "Activate the inspector on host and port in the format of `[[host:]port]`. See the security warning in https://nodejs.org/docs/latest-v22.x/api/cli.html#warning-binding-inspector-to-a-public-ipport-combination-is-insecure regarding the host parameter usage."
         },
-        { "type": "boolean" }
+        {
+          "type": "boolean"
+        }
       ]
     },
     "prebundle": {
       "description": "Enable and control the Vite-based development server's prebundling capabilities. To enable prebundling, the Angular CLI cache must also be enabled.",
       "default": true,
       "oneOf": [
-        { "type": "boolean" },
+        {
+          "type": "boolean"
+        },
         {
           "type": "object",
           "properties": {
             "exclude": {
               "description": "List of package imports that should not be prebundled by the development server. The packages will be bundled into the application code itself. Note: specifying `@foo/bar` marks all paths within the `@foo/bar` package as excluded, including sub-paths like `@foo/bar/baz`.",
               "type": "array",
-              "items": { "type": "string" }
+              "items": {
+                "type": "string"
+              }
             }
           },
           "additionalProperties": false,
-          "required": ["exclude"]
+          "required": [
+            "exclude"
+          ]
         }
       ]
+    },
+    "middlewareConfig": {
+      "type": "string",
+      "description": "Middleware configuration file."
     }
   },
   "additionalProperties": false,
-  "required": ["buildTarget"]
-}
+  "required": [
+    "buildTarget"
+  ]
+}

packages/angular/build/src/builders/dev-server/vite/server.ts

@@ -19,7 +19,7 @@ import {
   createRemoveIdPrefixPlugin,
 } from '../../../tools/vite/plugins';
 import { EsbuildLoaderOption, getDepOptimizationConfig } from '../../../tools/vite/utils';
-import { loadProxyConfiguration } from '../../../utils';
+import { loadMiddlewareConfiguration, loadProxyConfiguration } from '../../../utils';
 import { type ApplicationBuilderInternalOptions, JavaScriptTransformer } from '../internal';
 import type { NormalizedDevServerOptions } from '../options';
 import { DevServerExternalResultMetadata, OutputAssetRecord, OutputFileRecord } from './utils';
@@ -153,6 +153,19 @@ export async function setupServer(
     join(serverOptions.workspaceRoot, `.angular/vite-root`, serverOptions.buildTarget.project),
   );
 
+  if (serverOptions.middlewareConfig) {
+    const middleware = await loadMiddlewareConfiguration(
+      serverOptions.workspaceRoot,
+      serverOptions.middlewareConfig,
+    );
+
+    if (extensionMiddleware) {
+      extensionMiddleware = [...extensionMiddleware, ...middleware];
+    } else {
+      extensionMiddleware = middleware;
+    }
+  }
+
   /**
    * Required when using `externalDependencies` to prevent Vite load errors.
    *

packages/angular/build/src/utils/index.ts

@@ -10,3 +10,4 @@ export * from './normalize-asset-patterns';
 export * from './normalize-optimization';
 export * from './normalize-source-maps';
 export * from './load-proxy-config';
+export * from './load-middleware-config';

packages/angular/build/src/utils/load-middleware-config.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.dev/license
+ */
+import { existsSync } from 'node:fs';
+import { resolve } from 'node:path';
+import { pathToFileURL } from 'node:url';
+import type { Connect } from 'vite';
+import { assertIsError } from './error';
+import { loadEsmModule } from './load-esm';
+
+export async function loadMiddlewareConfiguration(
+  root: string,
+  middlewareConfig: string | undefined,
+): Promise<Connect.NextHandleFunction[]> {
+  if (!middlewareConfig) {
+    return [];
+  }
+
+  const middlewarePath = resolve(root, middlewareConfig);
+
+  if (!existsSync(middlewarePath)) {
+    throw new Error(`Middleware configuration file ${middlewarePath} does not exist.`);
+  }
+
+  let middlewareConfiguration;
+
+  try {
+    middlewareConfiguration = await import(pathToFileURL(middlewarePath).href);
+  } catch (e) {
+    assertIsError(e);
+    if (e.code !== 'ERR_REQUIRE_ASYNC_MODULE') {
+      throw e;
+    }
+
+    middlewareConfiguration = await loadEsmModule<{ default: unknown }>(
+      pathToFileURL(middlewarePath),
+    );
+  }
+
+  if ('default' in middlewareConfiguration) {
+    middlewareConfiguration = middlewareConfiguration.default;
+  }
+
+  return Array.isArray(middlewareConfiguration)
+    ? middlewareConfiguration
+    : [middlewareConfiguration];
+}

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

@@ -98,6 +98,7 @@ export function execute(
                 hmr: boolean;
                 allowedHosts: true | string[];
                 define: { [key: string]: string } | undefined;
+                middlewareConfig?: string;
               },
               builderName,
               (options, context, codePlugins) => {

packages/angular_devkit/build_angular/src/builders/dev-server/schema.json

@@ -103,7 +103,9 @@
           "type": "string",
           "description": "Activate the inspector on host and port in the format of `[[host:]port]`. See the security warning in https://nodejs.org/docs/latest-v22.x/api/cli.html#warning-binding-inspector-to-a-public-ipport-combination-is-insecure regarding the host parameter usage."
         },
-        { "type": "boolean" }
+        {
+          "type": "boolean"
+        }
       ]
     },
     "forceEsbuild": {
@@ -114,22 +116,34 @@
     "prebundle": {
       "description": "Enable and control the Vite-based development server's prebundling capabilities. To enable prebundling, the Angular CLI cache must also be enabled. This option has no effect when using the 'browser' or other Webpack-based builders.",
       "oneOf": [
-        { "type": "boolean" },
+        {
+          "type": "boolean"
+        },
         {
           "type": "object",
           "properties": {
             "exclude": {
               "description": "List of package imports that should not be prebundled by the development server. The packages will be bundled into the application code itself.",
               "type": "array",
-              "items": { "type": "string" }
+              "items": {
+                "type": "string"
+              }
             }
           },
           "additionalProperties": false,
-          "required": ["exclude"]
+          "required": [
+            "exclude"
+          ]
         }
       ]
+    },
+    "middlewareConfig": {
+      "type": "string",
+      "description": "Middleware configuration file."
     }
   },
   "additionalProperties": false,
-  "required": ["buildTarget"]
-}
+  "required": [
+    "buildTarget"
+  ]
+}

packages/angular_devkit/build_angular/src/builders/dev-server/tests/options/middleware-config_spec.ts

@@ -0,0 +1,88 @@
+/**
+ * @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.dev/license
+ */
+
+import { createServer } from 'node:http';
+import { executeDevServer } from '../../index';
+import { executeOnceAndFetch } from '../execute-fetch';
+import { describeServeBuilder } from '../jasmine-helpers';
+import { BASE_OPTIONS, DEV_SERVER_BUILDER_INFO } from '../setup';
+
+describeServeBuilder(executeDevServer, DEV_SERVER_BUILDER_INFO, (harness, setupTarget) => {
+  describe('option: "middlewareConfig"', () => {
+    beforeEach(async () => {
+      setupTarget(harness);
+
+      // Application code is not needed for these tests
+      await harness.writeFile('src/main.ts', '');
+    });
+
+    it('middleware configuration export single function (CommonJS)', async () => {
+      harness.useTarget('serve', {
+        ...BASE_OPTIONS,
+        middlewareConfig: 'middleware.config.js',
+      });
+      const proxyServer = await createProxyServer();
+      try {
+        await harness.writeFiles({
+          'middleware.config.js': `module.exports = (req, res, next) => { res.end('TEST_MIDDLEWARE'); next();}`,
+        });
+
+        const { result, response } = await executeOnceAndFetch(harness, '/test');
+
+        expect(result?.success).toBeTrue();
+        expect(await response?.text()).toContain('TEST_MIDDLEWARE');
+      } finally {
+        await proxyServer.close();
+      }
+    });
+
+    it('middleware configuration export an array of multiple functions (CommonJS)', async () => {
+      harness.useTarget('serve', {
+        ...BASE_OPTIONS,
+        middlewareConfig: 'middleware.config.js',
+      });
+      const proxyServer = await createProxyServer();
+      try {
+        await harness.writeFiles({
+          'middleware.config.js': `module.exports = [(req, res, next) => { next();}, (req, res, next) => { res.end('TEST_MIDDLEWARE'); next();}]`,
+        });
+
+        const { result, response } = await executeOnceAndFetch(harness, '/test');
+
+        expect(result?.success).toBeTrue();
+        expect(await response?.text()).toContain('TEST_MIDDLEWARE');
+      } finally {
+        await proxyServer.close();
+      }
+    });
+  });
+});
+
+/**
+ * Creates an HTTP Server used for proxy testing that provides a `/test` endpoint
+ * that returns a 200 response with a body of `TEST_API_RETURN`. All other requests
+ * will return a 404 response.
+ */
+async function createProxyServer() {
+  const proxyServer = createServer((request, response) => {
+    if (request.url?.endsWith('/test')) {
+      response.writeHead(200);
+      response.end('TEST_API_RETURN');
+    } else {
+      response.writeHead(404);
+      response.end();
+    }
+  });
+
+  await new Promise<void>((resolve) => proxyServer.listen(0, '127.0.0.1', resolve));
+
+  return {
+    address: proxyServer.address() as import('net').AddressInfo,
+    close: () => new Promise<void>((resolve) => proxyServer.close(() => resolve())),
+  };
+}