--headless has no effect for Firefox in some Linux environments

[vytas7]

I'd like to basically reopen #701 : even if --headless is set (moreover, it should be default on Linux), it has no effect.
geckodriver.log reads:

1609613050327   mozrunner::runner       INFO    Running command: "/usr/bin/firefox" "--marionette" "-foreground" "-no-remote" "-profile" "/tmp/rust_mozprofile0dBR8Z"

Using FirefoxOptions.headless (see the PoC patch below) works for me, but AFAICT it should be applied to more places (?), and not sure how that plays together with firefox_capabilities:

--- a/seleniumbase/core/browser_launcher.py
+++ b/seleniumbase/core/browser_launcher.py
@@ -690,7 +690,10 @@ def get_local_driver(
                                   "%s" % e)
                         sys.argv = sys_args  # Put back the original sys args
                 if "linux" in PLATFORM or not headless:
+                    firefox_options = webdriver.FirefoxOptions()
+                    firefox_options.headless = headless
                     firefox_driver = webdriver.Firefox(
+                        firefox_options=firefox_options,
                         firefox_profile=profile,
                         capabilities=firefox_capabilities)
                 else:

[vytas7]

FWIW, I'm using Ubuntu 16.04, Firefox 84.0 (64-bit), CPython 3.8 and selenium==3.141.0 in a virtual env.

Also seeing the same effect with the python:3.8 Docker image (by installing the firefox-esr Debian package since it's based on Debian Buster).

[mdmintz]

@vytas7 Should be fixed by #768 in seleniumbase v1.51.8 (https://github.com/seleniumbase/SeleniumBase/releases/tag/v1.51.8). Let me know if you have any issues with it.

[vytas7]

@mdmintz whoa, that was quick! 1.51.8 now works fine with both --headless and --headed 👍 🎉

(I've only reverted the issue title if you don't mind... I first ran into this on my Linux desktop, and not in Docker. I.e., it was working fine, but a Firefox window was popping up no matter what. Later, I do intend using this in Docker in CI.)