[BUG] Cannot remove header in `route.continue`

Context:

• Playwright Version: 1.20.1
• Operating System: Linux
• Node.js version: 17.8.0
• Browser: Chromium

Code Snippet

const playwright = require('playwright');

require('http').createServer((request, response) => {
        response.end('');
}).listen(8888);

(async () => {
        const browser = await playwright.chromium.launchPersistentContext('', {
                headless: false,
        });

        const page = await browser.newPage();

        await page.route('**/*', (route, request) => {
          // Override headers
          const headers = {
            ...request.headers(),
            foo: 'bar', // set "foo" header
            origin: undefined, // remove "origin" header
          };
          route.continue({headers});
        });

        await page.goto('http://localhost:8888/', { waitUntil: 'load' });
})();

Describe the bug

The example https://playwright.dev/docs/next/api/class-route#route-continue is broken.

node:internal/process/promises:279
            triggerUncaughtException(err, true /* fromPromise */);
            ^

route.continue: headers[7].value: expected string, got undefined
    at RouteHandler.handler (/home/szm/Desktop/cache/bug6.js:21:18)

Node.js v17.8.0

[yury-s]

Thanks for confirming. Setting to undefined should now delete headers. I looked at WebKit implementation and there is no simple way to make it remove/update origin header, I’ve filed a separate issue for that (https://github.com/microsoft/playwright/issues/13886) and will wait until there is more demand for this before implementing any suboptimal solutions.

[rwoll]

Thanks for the report! I repro’d locally.

Does using delete built-in before passing along the headers work for your use case?

const headers = {
  ...request.headers(),
  foo: 'bar'
};

delete headers['x-some-header'];
…

Regardless, we’ll either update the docs or make the doc example work!

---

Note from repro: The error is likely from our protocol type def: https://github.com/microsoft/playwright/blob/1471bb71776cf84223190e1552ee4e055db1547a/packages/playwright-core/src/protocol/protocol.yml#L2442