[BUG] Evaluate return partial object

[mattveraldi]

System info

• Playwright Version: [v1.32.3]
• Operating System: [Windows 11]
• Browser: [Chromium]
• Other info: GoJS e2e testing

Source code

• [x] I provided exact source code that allows reproducing the issue locally.

Config file

import { defineConfig, devices } from '@playwright/test';

/**
 * Read environment variables from file.
 * https://github.com/motdotla/dotenv
 */
// require('dotenv').config();

/**
 * See https://playwright.dev/docs/test-configuration.
 */
export default defineConfig({
  testDir: './tests',
  /* Run tests in files in parallel */
  fullyParallel: true,
  /* Fail the build on CI if you accidentally left test.only in the source code. */
  forbidOnly: !!process.env.CI,
  /* Retry on CI only */
  retries: process.env.CI ? 2 : 0,
  /* Opt out of parallel tests on CI. */
  workers: process.env.CI ? 1 : undefined,
  /* Reporter to use. See https://playwright.dev/docs/test-reporters */
  reporter: 'html',
  /* Shared settings for all the projects below. See https://playwright.dev/docs/api/class-testoptions. */
  use: {
    /* Base URL to use in actions like `await page.goto('/')`. */
    // baseURL: 'http://127.0.0.1:3000',

    /* Collect trace when retrying the failed test. See https://playwright.dev/docs/trace-viewer */
    trace: 'on-first-retry',
  },

  /* Configure projects for major browsers */
  projects: [
    {
      name: 'chromium',
      use: { ...devices['Desktop Chrome'] },
    },

    // {
    //   name: 'firefox',
    //   use: { ...devices['Desktop Firefox'] },
    // },

    // {
    //   name: 'webkit',
    //   use: { ...devices['Desktop Safari'] },
    // },

    /* Test against mobile viewports. */
    // {
    //   name: 'Mobile Chrome',
    //   use: { ...devices['Pixel 5'] },
    // },
    // {
    //   name: 'Mobile Safari',
    //   use: { ...devices['iPhone 12'] },
    // },

    /* Test against branded browsers. */
    // {
    //   name: 'Microsoft Edge',
    //   use: { ...devices['Desktop Edge'], channel: 'msedge' },
    // },
    // {
    //   name: 'Google Chrome',
    //   use: { ..devices['Desktop Chrome'], channel: 'chrome' },
    // },
  ],

  /* Run your local dev server before starting the tests */
  // webServer: {
  //   command: 'npm run start',
  //   url: 'http://127.0.0.1:3000',
  //   reuseExistingServer: !process.env.CI,
  // },
});

Test file (self-contained)

it('smoke test', async ({ page }) => {
  await page.goto('https://gojs.net/latest/samples/orgChartStatic.html');
  const diagram = await page.locator("#myDiagramDiv");
  let node = await diagram.evaluate((diagramWrapper) => diagramWrapper["goDiagram"].findNodeForKey(1));
  console.warn(node); // it works giving me a partial representation
  console.warn(node.data); // is undefined, but it shouldn't
  let nodeData = await diagram.evaluate((diagramWrapper) => diagramWrapper["goDiagram"].findNodeForKey(1)?.data);
  console.warn(nodeData) // it works
});

Steps

• [Run the test]
• [...]

Expected

node.data should work outside of the evaluate context as well as inside it.

Actual

node.data is undefined when accessed outside the evaluate context, but it has other properties.

[mxschmitt]

Investigation notes: Reason for this is because this libray does some prototype hacking internally, which can be tracked down to this minimal reproducible, imagine this below is what we do internally:

const myTest = {}
// without __proto__ it works as expected.
Object.defineProperties(myTest.__proto__, {
    data: {
        get: () => 42,
        set: () => {},
    }
})
// What we do internally to serialise results.
console.log(Object.getOwnPropertyDescriptors(myTest), Object.keys(Object.keys(myTest)))

I recommend for now to access the 'data' property manually directly. Would that work for you?

[mattveraldi]

Investigation notes: Reason for this is because this libray does some prototype hacking internally, which can be tracked down to this minimal reproducible, imagine this below is what we do internally:

const myTest = {}
// without __proto__ it works as expected.
Object.defineProperties(myTest.__proto__, {
    data: {
        get: () => 42,
        set: () => {},
    }
})
// What we do internally to serialise results.
console.log(Object.getOwnPropertyDescriptors(myTest), Object.keys(Object.keys(myTest)))

I recommend for now to access the 'data' property manually directly. Would that work for you?

I see the problem now... What I am doing at the moment is adding "data" manually in the return statement of the evaluate method, but that means that I have to do it for each "getter" in order to have a generic utility function for gojs nodes... Is there any possible workaround to this?

[mxschmitt]

There is unfortunately no easy way around this problem. Keep in mind that the JavaScript inside the page gets serialised with the Node.js runtime, see here: https://playwright.dev/docs/evaluating

So we do a best effort which fails in case of deep prototype getters.

Closing by that for now, since a workaround for this would be to return a property explicitly.

[mattveraldi]

@mxschmitt Ok thank you, just to know if I understood correctly... this the serializer that does the "prototype hacking" you was referring to?

[mxschmitt]

The prototype hacking with the getters is done with this gojs library. I didn't find their source online, but internally they do things like ma.Object.defineProperties(W.prototype, { (minified source). And we internally serialise using this while Object.keys does not work for this library.

[mattveraldi]

Thank you!