`Accept-Language` header gets ignored by Playwright

[wrobelda]

Describe the bug I am trying to force a specific language version of a website, which they determine based on the Accept-Language header. However, Playwright seems to ignore it altogether. I tested independently using my desktop browser and setting the Accept-Language there works as expected: the specific language version of a website is shown depending on the header's content.

Version v0.40.1.1

To Reproduce

Steps to reproduce the behavior:

1. Go to any website that serves different language based on Accept-Language (i.e. outside of any cookie that could store that information)
2. Set the Accept-Language to an arbitrary language that would request a said version of the website
3. Notice that it has no effect

Expected behavior Accept-Language should be passed and applied to every Playwright request.

[skleeschulte]

Maybe this helps someone:

• I followed https://github.com/dgtlmoon/changedetection.io/wiki/Playwright-content-fetcher#docker-compose-based and the comments in the compose file example to enable Playwright in Docker (using compose file).
• I changed the PLAYWRIGHT_DRIVER_URL to ws://playwright-chrome:3000/?stealth=1&--disable-web-security=true&--accept-lang=de-DE,de to set the browsers accepted language to German. Not sure if de-DE, de or both is allowed/working here, did not test further.
• This is working in my case. Tested with docker image ghcr.io/dgtlmoon/changedetection.io:0.45.2.

I found it hard to understand how this works. This is what I found:

• PLAYWRIGHT_DRIVER_URL is used as an argument to connect_over_cdp (https://github.com/dgtlmoon/changedetection.io/blob/5cccccb0b639d5b89f9f8da89158bae4f610f89e/changedetectionio/blueprint/browser_steps/__init__.py#L63).
• connect_over_cdp is a function in Playwright for Python (https://playwright.dev/python/docs/api/class-browsertype#browser-type-connect-over-cdp).
• CDP is short for Chrome DevTools Protocol.
• The playwright-chrome-service in the docker compose file is using the browserless/chrome docker image (https://github.com/browserless/chrome#docker), with documentation here: https://www.browserless.io/docs/start
• browserless allows passing chrome launch options (= command line arguments?) as query-string parameters in the endpoint url: https://www.browserless.io/docs/chrome-flags
• The Accept-Language can be set via chrome command line argument like this: --accept-lang=en-GB,en-US (https://stackoverflow.com/a/74576386/846987)