feat(dev-server): add "ping" route

src/compiler/config/test/validate-dev-server.spec.ts

@@ -276,4 +276,32 @@ describe('validateDevServer', () => {
     const { config } = validateConfig(inputConfig, mockLoadConfigInit());
     expect(config.devServer.prerenderConfig).toBe(wwwOutputTarget.prerenderConfig);
   });
+
+  describe('pingRoute', () => {
+    it('should default to /ping', () => {
+      // Ensure the pingRoute is not set in the inputConfig so we know we're testing the
+      // default value added during validation
+      delete inputConfig.devServer.pingRoute;
+      const { config } = validateConfig(inputConfig, mockLoadConfigInit());
+      expect(config.devServer.pingRoute).toBe('/ping');
+    });
+
+    it('should set user defined pingRoute', () => {
+      inputConfig.devServer = { ...inputDevServerConfig, pingRoute: '/my-ping' };
+      const { config } = validateConfig(inputConfig, mockLoadConfigInit());
+      expect(config.devServer.pingRoute).toBe('/my-ping');
+    });
+
+    it('should prefix pingRoute with a "/"', () => {
+      inputConfig.devServer = { ...inputDevServerConfig, pingRoute: 'my-ping' };
+      const { config } = validateConfig(inputConfig, mockLoadConfigInit());
+      expect(config.devServer.pingRoute).toBe('/my-ping');
+    });
+
+    it('should clear ping route if set to null', () => {
+      inputConfig.devServer = { ...inputDevServerConfig, pingRoute: null };
+      const { config } = validateConfig(inputConfig, mockLoadConfigInit());
+      expect(config.devServer.pingRoute).toBe(null);
+    });
+  });
 });

src/compiler/config/validate-dev-server.ts

@@ -29,6 +29,16 @@ export const validateDevServer = (config: d.ValidatedConfig, diagnostics: d.Diag
 
   devServer.address = devServer.address.split('/')[0];
 
+  // Validate "ping" route option
+  if (devServer.pingRoute !== null) {
+    let pingRoute = isString(devServer.pingRoute) ? devServer.pingRoute : '/ping';
+    if (!pingRoute.startsWith('/')) {
+      pingRoute = `/${pingRoute}`;
+    }
+
+    devServer.pingRoute = pingRoute;
+  }
+
   // split on `:` to get the domain and the (possibly present) port
   // separately. we've already sliced off the protocol (if present) above
   // so we can safely split on `:` here.

src/declarations/stencil-public-compiler.ts

@@ -651,6 +651,15 @@ export interface DevServerConfig extends StencilDevServerConfig {
   prerenderConfig?: string;
   protocol?: 'http' | 'https';
   srcIndexHtml?: string;
+
+  /**
+   * Route to be used for the "ping" sub-route of the Stencil dev server.
+   * This route will return a 200 status code once the Stencil build has finished.
+   * Setting this to `null` will disable the ping route.
+   *
+   * Defaults to `/ping`
+   */
+  pingRoute?: string | null;
 }
 
 export interface HistoryApiFallback {

src/dev-server/request-handler.ts

@@ -26,6 +26,21 @@ export function createRequestHandler(devServerConfig: d.DevServerConfig, serverC
           return serverCtx.serve302(req, res);
         }
 
+        if (devServerConfig.pingRoute !== null && req.pathname === devServerConfig.pingRoute) {
+          return serverCtx
+            .getBuildResults()
+            .then((result) => {
+              if (!result.hasSuccessfulBuild) {
+                return serverCtx.serve500(incomingReq, res, 'Build not successful', 'build error');
+              }
+
+              res.writeHead(200, 'OK');
+              res.write('OK');
+              res.end();
+            })
+            .catch(() => serverCtx.serve500(incomingReq, res, 'Error getting build results', 'ping error'));
+        }
+
         if (isDevClient(req.pathname) && devServerConfig.websocket) {
           return serveDevClient(devServerConfig, serverCtx, req, res);
         }

src/dev-server/test/req-handler.spec.ts

@@ -439,6 +439,32 @@ describe('request-handler', () => {
       expect(h).toBe(`88mph<iframe></iframe>`);
     });
   });
+
+  describe('pingRoute', () => {
+    it('should return a 200 for successful build', async () => {
+      serverCtx.getBuildResults = () =>
+        Promise.resolve({ hasSuccessfulBuild: true }) as Promise<d.CompilerBuildResults>;
+
+      const handler = createRequestHandler(devServerConfig, serverCtx);
+
+      req.url = '/ping';
+
+      await handler(req, res);
+      expect(res.$statusCode).toBe(200);
+    });
+
+    it('should return a 500 for unsuccessful build', async () => {
+      serverCtx.getBuildResults = () =>
+        Promise.resolve({ hasSuccessfulBuild: false }) as Promise<d.CompilerBuildResults>;
+
+      const handler = createRequestHandler(devServerConfig, serverCtx);
+
+      req.url = '/ping';
+
+      await handler(req, res);
+      expect(res.$statusCode).toBe(500);
+    });
+  });
 });
 
 interface TestServerResponse extends ServerResponse {