feat(@angular-devkit/build-angular): add process.env.PORT support to the dev server

Make possible to set the dev server port via `process.env.PORT`.

Handles issue angular#32236.

Author: hawkgs

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

@@ -186,6 +186,16 @@ case.
     );
   }
 
+  // Overwrite port, if process.env.PORT is available.
+  if (process.env.PORT) {
+    const envPort = Number(process.env.PORT);
+
+    if (!isNaN(envPort)) {
+      normalizedOptions.port = envPort;
+      context.logger.info('process.env.PORT detected. Port set to ' + envPort);
+    }
+  }
+
   normalizedOptions.port = await checkPort(normalizedOptions.port, normalizedOptions.host);
 
   return {

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

@@ -107,6 +107,23 @@ describeServeBuilder(
           );
         }
       });
+
+      it('should be overwritten by process.env.PORT if it exists', async () => {
+        harness.useTarget('serve', {
+          ...BASE_OPTIONS,
+          port: 8000,
+        });
+
+        process.env.PORT = '4201';
+
+        const { result, response } = await executeOnceAndFetch(harness, '/');
+
+        expect(result?.success).toBeTrue();
+        expect(getResultPort(result)).toBe('4201');
+        expect(await response?.text()).toContain('<title>');
+
+        delete process.env.PORT;
+      });
     });
   },
 );