test: extract RemoteControlApp to spec-helpers (#24020)

spec-main/spec-helpers.ts

@@ -1,4 +1,78 @@
+import * as childProcess from 'child_process';
+import * as path from 'path';
+import * as http from 'http';
+import * as v8 from 'v8';
+
 export const ifit = (condition: boolean) => (condition ? it : it.skip);
 export const ifdescribe = (condition: boolean) => (condition ? describe : describe.skip);
 
 export const delay = (time: number) => new Promise(resolve => setTimeout(resolve, time));
+
+type CleanupFunction = (() => void) | (() => Promise<void>)
+const cleanupFunctions: CleanupFunction[] = [];
+export async function runCleanupFunctions () {
+  for (const cleanup of cleanupFunctions) {
+    const r = cleanup();
+    if (r instanceof Promise) { await r; }
+  }
+  cleanupFunctions.length = 0;
+}
+
+export function defer (f: CleanupFunction) {
+  cleanupFunctions.push(f);
+}
+
+class RemoteControlApp {
+  process: childProcess.ChildProcess;
+  port: number;
+
+  constructor (proc: childProcess.ChildProcess, port: number) {
+    this.process = proc;
+    this.port = port;
+  }
+
+  remoteEval = (js: string): Promise<any> => {
+    return new Promise((resolve, reject) => {
+      const req = http.request({
+        host: '127.0.0.1',
+        port: this.port,
+        method: 'POST'
+      }, res => {
+        const chunks = [] as Buffer[];
+        res.on('data', chunk => { chunks.push(chunk); });
+        res.on('end', () => {
+          const ret = v8.deserialize(Buffer.concat(chunks));
+          if (Object.prototype.hasOwnProperty.call(ret, 'error')) {
+            reject(new Error(`remote error: ${ret.error}\n\nTriggered at:`));
+          } else {
+            resolve(ret.result);
+          }
+        });
+      });
+      req.write(js);
+      req.end();
+    });
+  }
+
+  remotely = (script: Function, ...args: any[]): Promise<any> => {
+    return this.remoteEval(`(${script})(...${JSON.stringify(args)})`);
+  }
+}
+
+export async function startRemoteControlApp () {
+  const appPath = path.join(__dirname, 'fixtures', 'apps', 'remote-control');
+  const appProcess = childProcess.spawn(process.execPath, [appPath]);
+  appProcess.stderr.on('data', d => {
+    process.stderr.write(d);
+  });
+  const port = await new Promise<number>(resolve => {
+    appProcess.stdout.on('data', d => {
+      const m = /Listening: (\d+)/.exec(d.toString());
+      if (m && m[1] != null) {
+        resolve(Number(m[1]));
+      }
+    });
+  });
+  defer(() => { appProcess.kill('SIGINT'); });
+  return new RemoteControlApp(appProcess, port);
+}