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How to use createOnceHandler method in Playwright Internal

Best JavaScript code snippet using playwright-internal

history_provider.js

Source:history_provider.js

...107      // teardown the listener108      teardownFn();109    });110    it('should call handler on state change', done => {111      createOnceHandler(history, done, loc => {112        expect(loc).to.be.a('object');113      });114      history.push({});115    });116    it('should pass location object to handler', done => {117      createOnceHandler(history, done, location => {118        expect(location.pathname).to.be.a('string');119        expect(location.hash).to.be.a('string');120        expect(location.state).to.be.an('object');121        expect(location.action).to.equal('push');122      });123      history.push(state);124    });125    it('should pass decompressed state to handler', done => {126      createOnceHandler(history, done, ({ state: curState }) => {127        expect(curState).to.eql(state);128      });129      history.push(state);130    });131    it('should pass in the previous location object to handler', done => {132      createOnceHandler(history, done, (location, prevLocation) => {133        expect(prevLocation.pathname).to.be.a('string');134        expect(prevLocation.hash).to.be.a('string');135        expect(prevLocation.state).to.be(null);136        expect(prevLocation.action).to.equal('push');137      });138      history.push(state);139    });140  });141  describe('resetOnChange', () => {142    // the history onChange handler was made async and now there's no way to know when the handler was called143    // TODO: restore these tests.144    it.skip('removes listeners', () => {145      const createHandler = () => {146        let callCount = 0;...

events.js

Source:events.js

...49      if (isUndef(cur.fns)) {50        cur = on[name] = createFnInvoker(cur, vm)51      }52      if (isTrue(event.once)) {53        cur = on[name] = createOnceHandler(event.name, cur, event.capture)54      }55      add(event.name, cur, event.capture, event.passive, event.params)56    } else if (cur !== old) {57      old.fns = cur58      on[name] = old59    }60  }61  for (name in oldOn) {62    if (isUndef(on[name])) {63      event = normalizeEvent(name)64      remove(event.name, oldOn[name], event.capture)65    }66  }67}...

Using AI Code Generation

1const { createOnceHandler } = require('playwright/lib/server/frames');2const { chromium } = require('playwright');3(async () => {4  const browser = await chromium.launch();5  const context = await browser.newContext();6  const page = await context.newPage();7  const frame = page.mainFrame();8  const handler = createOnceHandler(frame);9  frame.on('load', handler);10  await frame.waitForLoadState();11  await page.screenshot({ path: 'wikipedia.png' });12  await browser.close();13})();

Using AI Code Generation

1const { createOnceHandler } = require('playwright/lib/server/instrumentation');2const { chromium } = require('playwright');3(async () => {4  const browser = await chromium.launch();5  const page = await browser.newPage();6  const onceHandler = createOnceHandler();7  await page.exposeBinding('onceHandler', onceHandler);8  await page.evaluate(async () => {9    window.addEventListener('message', event => {10      if (event.data.type === 'onceHandler') {11        window.onceHandler(event.data.data);12      }13    });14  });15  const result = await onceHandler(() => page.evaluate(() => {16    window.postMessage({ type: 'onceHandler', data: 42 }, '*');17  }));18  console.log(result);19  await browser.close();20})();21const { chromium } = require('playwright');22(async () => {23  const browser = await chromium.launch();24  const page = await browser.newPage();25  const result = await page.evaluate(() => {26    return new Promise(resolve => {27      window.addEventListener('message', event => {28        if (event.data.type === 'onceHandler') {29          resolve(event.data.data);30        }31      });32      window.postMessage({ type: 'onceHandler', data: 42 }, '*');33    });34  });35  console.log(result);36  await browser.close();37})();

Using AI Code Generation

1const { createOnceHandler } = require('@playwright/test/lib/server/progress');2const { chromium } = require('playwright');3(async () => {4  const browser = await chromium.launch();5  const context = await browser.newContext();6  const page = await context.newPage();7  await page.screenshot({ path: 'example.png' });8  await browser.close();9})();10const { createOnceHandler } = require('@playwright/test/lib/server/progress');11const { chromium } = require('playwright');12(async () => {13  const browser = await chromium.launch();14  const context = await browser.newContext();15  const page = await context.newPage();16  await page.screenshot({ path: 'example.png' });17  await browser.close();18})();

Using AI Code Generation

1const { createOnceHandler } = require('@playwright/test/lib/server/trace/recorder/traceEvents');2const { Page } = require('@playwright/test/lib/server/page');3const { Frame } = require('@playwright/test/lib/server/frame');4const { createGuid } = require('@playwright/test/lib/utils/utils');5const { Context } = require('@playwright/test/lib/server/browserContext');6const { guid } = createGuid();7const context = new Context(null, guid);8const page = new Page(context, guid);9const frame = new Frame(page, guid);10const handler = createOnceHandler(frame, 'page');11frame._channel.on('page', handler);12frame._channel.emit('page', { frameId: '123' });13frame._channel.emit('page', { frameId: '456' });14frame._channel.off('page', handler);15frame._channel.emit('page', { frameId: '789' });16frame._channel.emit('page', { frameId: '101' });

Using AI Code Generation

1const { createOnceHandler } = require('playwright/lib/server/chromium/crConnection');2const { helper } = require('playwright/lib/helper');3const { chromium } = require('playwright');4(async () => {5  const browser = await chromium.launch();6  const page = await browser.newPage();7  await browser.close();8})();9const { createOnceHandler } = require('playwright/lib/server/chromium/crConnection');10const { helper } = require('playwright/lib/helper');11const { chromium } = require('playwright');12(async () => {13  const browser = await chromium.launch();14  const page = await browser.newPage();15  await browser.close();16})();

Using AI Code Generation

1const { createOnceHandler } = require('playwright/lib/server/frames');2const { Frame } = require('playwright/lib/server/page');3const handler = createOnceHandler();4const frame = new Frame();5frame._page._onFrameDetached.add(handler);6const frameDetached = handler.promise;7const frame = await frameDetached;8console.log(frame.url());

Using AI Code Generation

1const createOnceHandler = require('@playwright/test/lib/server/createOnceHandler');2const server = await testWorker._browserServer;3const handler = createOnceHandler(async (req, res) => {4  res.end('done');5});6server.route('/path', handler);7test('my test', async ({testInfo}) => {8  const testWorker = testInfo.workers[testInfo.workerIndex];9});

Using AI Code Generation

1const { createOnceHandler } = require('@playwright/test/lib/server/inspector');2const handler = createOnceHandler(event => console.log(event));3const WebSocket = require('ws');4const wss = new WebSocket.Server({ port: 8080 });5wss.on('connection', function connection(ws) {6  ws.on('message', function incoming(message) {7    const event = JSON.parse(message);8    handler(event);9  });10});11wss.on('listening', function listening() {12  console.log('Server started');13});14const WebSocket = require('ws');15ws.on('open', function open() {16  ws.send(JSON.stringify({ type: 'event1' }));17  ws.send(JSON.stringify({ type: 'event2' }));18  ws.send(JSON.stringify({ type: 'event1' }));19});20ws.on('message', function incoming(data) {21  console.log(data);22});23{ type: 'event1' }24{ type: 'event2' }25const { createOnceHandler } = require('@playwright/test/lib/server/inspector');26const handler = createOnceHandler(event => console.log(event));27const WebSocket = require('ws');28const wss = new WebSocket.Server({ port: 8080 });29wss.on('connection', function connection(ws) {30  ws.on('message', function incoming(message) {31    const event = JSON.parse(message);32    handler(event);33  });34});35wss.on('listening', function listening() {36  console.log('Server started');37});38const WebSocket = require('ws');39ws.on('open', function open() {40  ws.send(JSON.stringify({

StackOverFlow community discussions

Questions

Discussion

Is it possible to get the selector from a locator object in playwright?

How to run a list of test suites in a single file concurrently in jest?

firefox browser does not start in playwright

Jest + Playwright - Test callbacks of event-based DOM library

firefox browser does not start in playwright

Running Playwright in Azure Function

Well this is one way, but not sure if it will work for all possible locators!.

// Get a selector from a playwright locator
import { Locator } from "@playwright/test";
export function extractSelector(locator: Locator) {
    const selector = locator.toString();
    const parts = selector.split("@");
    if (parts.length !== 2) { throw Error("extractSelector: susupect that this is not a locator"); }
    if (parts[0] !== "Locator") { throw Error("extractSelector: did not find locator"); }
    return parts[1];
}

https://stackoverflow.com/questions/72044959/is-it-possible-to-get-the-selector-from-a-locator-object-in-playwright

Assuming you are not running test with the --runinband flag, the simple answer is yes but it depends ????

There is a pretty comprehensive GitHub issue jest#6957 that explains certain cases of when tests are run concurrently or in parallel. But it seems to depend on a lot of edge cases where jest tries its best to determine the fastest way to run the tests given the circumstances.

To my knowledge there is no way to force jest to run in parallel.

Aside

Have you considered using playwright instead of puppeteer with jest? Playwright has their own internally built testing library called @playwright/test that is used in place of jest with a similar API. This library allows for explicitly defining test groups in a single file to run in parallel (i.e. test.describe.parallel) or serially (i.e. test.describe.serial). Or even to run all tests in parallel via a config option.

// parallel
test.describe.parallel('group', () => {
  test('runs in parallel 1', async ({ page }) => {});
  test('runs in parallel 2', async ({ page }) => {});
});

// serial
test.describe.serial('group', () => {
  test('runs first', async ({ page }) => {});
  test('runs second', async ({ page }) => {});
});

https://stackoverflow.com/questions/73497773/how-to-run-a-list-of-test-suites-in-a-single-file-concurrently-in-jest

I found the error. It was because of some missing libraries need. I discovered this when I downgraded playwright to version 1.9 and ran the the code then this was the error msg:

(node:12876) UnhandledPromiseRejectionWarning: browserType.launch: Host system is missing dependencies!

Some of the Universal C Runtime files cannot be found on the system. You can fix
that by installing Microsoft Visual C++ Redistributable for Visual Studio from:
https://support.microsoft.com/en-us/help/2977003/the-latest-supported-visual-c-downloads

Full list of missing libraries:
    vcruntime140.dll
    msvcp140.dll
Error
    at Object.captureStackTrace (D:\Projects\snkrs-play\node_modules\playwright\lib\utils\stackTrace.js:48:19)
    at Connection.sendMessageToServer (D:\Projects\snkrs-play\node_modules\playwright\lib\client\connection.js:69:48)
    at Proxy.<anonymous> (D:\Projects\snkrs-play\node_modules\playwright\lib\client\channelOwner.js:64:61)
    at D:\Projects\snkrs-play\node_modules\playwright\lib\client\browserType.js:64:67
    at BrowserType._wrapApiCall (D:\Projects\snkrs-play\node_modules\playwright\lib\client\channelOwner.js:77:34)
    at BrowserType.launch (D:\Projects\snkrs-play\node_modules\playwright\lib\client\browserType.js:55:21)
    at D:\Projects\snkrs-play\index.js:4:35
    at Object.<anonymous> (D:\Projects\snkrs-play\index.js:7:3)
    at Module._compile (internal/modules/cjs/loader.js:1063:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1092:10)
(Use `node --trace-warnings ...` to show where the warning was created)
(node:12876) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 1)
(node:12876) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

A list of missing libraries was provided. After successful installments, firefox ran fine. I upgraded again to version 1.10 and firefox still works.

https://stackoverflow.com/questions/66984974/firefox-browser-does-not-start-in-playwright

This question is quite close to a "need more focus" question. But let's try to give it some focus:

Does Playwright has access to the cPicker object on the page? Does it has access to the window object?

Yes, you can access both cPicker and the window object inside an evaluate call.

Should I trigger the events from the HTML file itself, and in the callbacks, print in the DOM the result, in some dummy-element, and then infer from that dummy element text that the callbacks fired?

Exactly, or you can assign values to a javascript variable:

const cPicker = new ColorPicker({
  onClickOutside(e){
  },
  onInput(color){
    window['color'] = color;
  },
  onChange(color){
    window['result'] = color;
  }
})

And then

it('Should call all callbacks with correct arguments', async() => {
    await page.goto(`http://localhost:5000/tests/visual/basic.html`, {waitUntil:'load'})

    // Wait until the next frame
    await page.evaluate(() => new Promise(requestAnimationFrame))

    // Act
   
    // Assert
    const result = await page.evaluate(() => window['color']);
    // Check the value
})

https://stackoverflow.com/questions/65477895/jest-playwright-test-callbacks-of-event-based-dom-library

I found the error. It was because of some missing libraries need. I discovered this when I downgraded playwright to version 1.9 and ran the the code then this was the error msg:

(node:12876) UnhandledPromiseRejectionWarning: browserType.launch: Host system is missing dependencies!

Some of the Universal C Runtime files cannot be found on the system. You can fix
that by installing Microsoft Visual C++ Redistributable for Visual Studio from:
https://support.microsoft.com/en-us/help/2977003/the-latest-supported-visual-c-downloads

Full list of missing libraries:
    vcruntime140.dll
    msvcp140.dll
Error
    at Object.captureStackTrace (D:\Projects\snkrs-play\node_modules\playwright\lib\utils\stackTrace.js:48:19)
    at Connection.sendMessageToServer (D:\Projects\snkrs-play\node_modules\playwright\lib\client\connection.js:69:48)
    at Proxy.<anonymous> (D:\Projects\snkrs-play\node_modules\playwright\lib\client\channelOwner.js:64:61)
    at D:\Projects\snkrs-play\node_modules\playwright\lib\client\browserType.js:64:67
    at BrowserType._wrapApiCall (D:\Projects\snkrs-play\node_modules\playwright\lib\client\channelOwner.js:77:34)
    at BrowserType.launch (D:\Projects\snkrs-play\node_modules\playwright\lib\client\browserType.js:55:21)
    at D:\Projects\snkrs-play\index.js:4:35
    at Object.<anonymous> (D:\Projects\snkrs-play\index.js:7:3)
    at Module._compile (internal/modules/cjs/loader.js:1063:30)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1092:10)
(Use `node --trace-warnings ...` to show where the warning was created)
(node:12876) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 1)
(node:12876) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.

A list of missing libraries was provided. After successful installments, firefox ran fine. I upgraded again to version 1.10 and firefox still works.

https://stackoverflow.com/questions/66984974/firefox-browser-does-not-start-in-playwright

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