core(fr): cleanup driver on run completion

lighthouse-core/fraggle-rock/gather/driver.js

@@ -28,6 +28,7 @@ const defaultSession = {
   addSessionAttachedListener: throwNotConnectedFn,
   removeSessionAttachedListener: throwNotConnectedFn,
   sendCommand: throwNotConnectedFn,
+  dispose: throwNotConnectedFn,
 };
 
 /** @implements {LH.Gatherer.FRTransitionalDriver} */
@@ -72,6 +73,12 @@ class Driver {
     this._executionContext = new ExecutionContext(this._session);
     this._fetcher = new Fetcher(this._session, this._executionContext);
   }
+
+  /** @return {Promise<void>} */
+  async disconnect() {
+    if (!this._session) return;
+    await this._session.dispose();
+  }
 }
 
 module.exports = Driver;

lighthouse-core/fraggle-rock/gather/navigation-runner.js

@@ -262,6 +262,8 @@ async function _navigations({driver, config, requestedUrl, baseArtifacts, comput
 async function _cleanup({requestedUrl, driver, config}) {
   const didResetStorage = !config.settings.disableStorageReset;
   if (didResetStorage) await storage.clearDataForOrigin(driver.defaultSession, requestedUrl);
+
+  await driver.disconnect();
 }
 
 /**

lighthouse-core/fraggle-rock/gather/session.js

@@ -163,6 +163,15 @@ class ProtocolSession {
       if (timeout) clearTimeout(timeout);
     });
   }
+
+  /**
+   * Disposes of a session so that it can no longer talk to Chrome.
+   * @return {Promise<void>}
+   */
+  async dispose() {
+    this._session.removeAllListeners();
+    await this._session.detach();
+  }
 }
 
 module.exports = ProtocolSession;

lighthouse-core/fraggle-rock/gather/snapshot-runner.js

@@ -45,6 +45,8 @@ async function snapshot(options) {
         settings: config.settings,
       });
 
+      await driver.disconnect();
+
       const artifacts = await awaitArtifacts(artifactState);
       return finalizeArtifacts(baseArtifacts, artifacts);
     },

lighthouse-core/fraggle-rock/gather/timespan-runner.js

@@ -58,6 +58,7 @@ async function startTimespan(options) {
           await collectPhaseArtifacts({phase: 'stopSensitiveInstrumentation', ...phaseOptions});
           await collectPhaseArtifacts({phase: 'stopInstrumentation', ...phaseOptions});
           await collectPhaseArtifacts({phase: 'getArtifact', ...phaseOptions});
+          await driver.disconnect();
 
           const artifacts = await awaitArtifacts(artifactState);
           return finalizeArtifacts(baseArtifacts, artifacts);

lighthouse-core/gather/driver.js

@@ -127,6 +127,11 @@ class Driver {
     return this._connection.disconnect();
   }
 
+  /** @return {Promise<void>} */
+  dispose() {
+    return this.disconnect();
+  }
+
   /**
    * Get the browser WebSocket endpoint for devtools protocol clients like Puppeteer.
    * Only works with WebSocket connection, not extension or devtools.

lighthouse-core/test/fraggle-rock/gather/driver-test.js

@@ -88,3 +88,16 @@ describe('.fetcher', () => {
     expect(driver.fetcher).toBeTruthy();
   });
 });
+
+describe('.disconnect', () => {
+  it('should do nothing if called before connect', async () => {
+    await driver.disconnect();
+  });
+
+  it('should invoke session dispose', async () => {
+    await driver.connect();
+    const dispose = driver.defaultSession.dispose = jest.fn();
+    await driver.disconnect();
+    expect(dispose).toHaveBeenCalled();
+  });
+});

lighthouse-core/test/fraggle-rock/gather/mock-driver.js

@@ -33,6 +33,7 @@ function createMockSession() {
     removeProtocolMessageListener: jest.fn(),
     addSessionAttachedListener: createMockOnFn(),
     removeSessionAttachedListener: jest.fn(),
+    dispose: jest.fn(),
 
     /** @return {LH.Gatherer.FRProtocolSession} */
     asSession() {
@@ -131,6 +132,7 @@ function createMockDriver() {
     url: () => page.url(),
     defaultSession: session,
     connect: jest.fn(),
+    disconnect: jest.fn(),
     executionContext: context.asExecutionContext(),
 
     /** @return {Driver} */

lighthouse-core/test/fraggle-rock/gather/session-test.js

@@ -103,6 +103,20 @@ describe('ProtocolSession', () => {
     });
   }
 
+  describe('.dispose', () => {
+    it('should detach from the session', async () => {
+      const detach = jest.fn();
+      const removeAllListeners = jest.fn();
+      // @ts-expect-error - we want to use a more limited test.
+      puppeteerSession = {detach, emit: jest.fn(), removeAllListeners};
+      session = new ProtocolSession(puppeteerSession);
+
+      await session.dispose();
+      expect(detach).toHaveBeenCalled();
+      expect(removeAllListeners).toHaveBeenCalled();
+    });
+  });
+
   describe('.addProtocolMessageListener', () => {
     it('should listen for any event', () => {
       // @ts-expect-error - we want to use a more limited test of a real event emitter.

types/gatherer.d.ts

@@ -34,6 +34,7 @@ declare module Gatherer {
     removeSessionAttachedListener(callback: (session: FRProtocolSession) => void): void
     off<TEvent extends keyof LH.CrdpEvents>(event: TEvent, callback: (...args: LH.CrdpEvents[TEvent]) => void): void;
     sendCommand<TMethod extends keyof LH.CrdpCommands>(method: TMethod, ...params: LH.CrdpCommands[TMethod]['paramsType']): Promise<LH.CrdpCommands[TMethod]['returnType']>;
+    dispose(): Promise<void>;
   }
 
   /** The limited driver interface shared between pre and post Fraggle Rock Lighthouse. */