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

[szmarczak]

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

[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:

playwright/packages/playwright-core/src/protocol/protocol.yml

Line 2442 in 1471bb7

items: NameValue

[szmarczak]

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

It doesn't. I guess the headers are merged.

[Horsty80]

I opened an issue #13527 , maybe it's the same issue than here with the route.continue()

[yury-s]

It doesn't. I guess the headers are merged.

I can only reproduce it in WebKit, the origin header is deleted fine in Chromium and Firefox, adding a test for that.

Can you share a code snippet that reproduces it in Chromium with delete headers['origin']?

[szmarczak]

Yury Semikhatsky (@yury-s) Please note that I'm removing the origin header

[yury-s]

Yury Semikhatsky (@yury-s) Please note that I'm removing the origin header

This is being addressed separately (setting a field to undefined will be treated as deleting it, currently it throws 'route.continue: headers[5].value: expected string, got undefined'). You mentioned above that calling delete didn't work for you, did we get it wrong?

[szmarczak]

Pardon me, delete headers.origin works like a charm. For some reason I was testing delete headers['user-agent'] instead.

So yeah, this issue is just about the undefined error.