feat(@angular-devkit/build-angular): add watch mode to server

packages/angular_devkit/build_angular/src/server/index.ts

@@ -85,7 +85,14 @@ export class ServerBuilder implements Builder<BuildWebpackServerSchema> {
         };
 
         try {
-          webpackCompiler.run(callback);
+          if (options.watch) {
+            const watching = webpackCompiler.watch({ poll: options.poll }, callback);
+
+            // Teardown logic. Close the watcher when unsubscribed from.
+            return () => watching.close(() => { });
+          } else {
+            webpackCompiler.run(callback);
+          }
         } catch (err) {
           if (err) {
             this.context.logger.error(

packages/angular_devkit/build_angular/src/server/schema.d.ts

@@ -117,6 +117,14 @@ export interface BuildWebpackServerSchema {
    * Use file name for lazy loaded chunks.
    */
   namedChunks?: boolean;
+  /**
+   * Run build when files change.
+   */
+  watch?: boolean;
+    /**
+   * Enable and define the file watching poll time period in milliseconds.
+   */
+  poll?: number;
 }
 
 /**

packages/angular_devkit/build_angular/src/server/schema.json

@@ -157,6 +157,15 @@
         "type": "string"
       },
       "default": []
+    },
+    "watch": {
+      "type": "boolean",
+      "description": "Run build when files change.",
+      "default": false
+    },
+    "poll": {
+      "type": "number",
+      "description": "Enable and define the file watching poll time period in milliseconds."
     }
   },
   "additionalProperties": false,
@@ -202,6 +211,6 @@
         }
       ]
     }
-    
+
   }
 }

packages/angular_devkit/build_angular/test/server/base_spec_large.ts

@@ -45,4 +45,18 @@ describe('Server Builder', () => {
       }),
     ).toPromise().then(done, done.fail);
   }, Timeout.Standard);
+
+  it('runs watch mode', (done) => {
+    const overrides = { watch: true };
+
+    runTargetSpec(host, { project: 'app', target: 'server' }, overrides).pipe(
+      tap((buildEvent) => {
+        expect(buildEvent.success).toBe(true);
+
+        const fileName = join(outputPath, 'main.js');
+        const content = virtualFs.fileBufferToString(host.scopedSync().read(normalize(fileName)));
+        expect(content).toMatch(/AppServerModuleNgFactory/);
+      }),
+    ).subscribe(undefined, done.fail, done);
+  }, Timeout.Standard);
 });