Firefox ignores default intl.accept_languages value

[Orzech]

1) Description: Ubuntu 16.04 LTS
Release: 16.04

2) firefox:
  Zainstalowana: 46.0+build5-0ubuntu0.16.04.2
  Kandydująca: 46.0+build5-0ubuntu0.16.04.2

3) Firefox should send Accept-Language header containing "pl,en-US;q=0.7,en;q=0.3".

4) Firefox sends Accept-Language header in the form of "en-US,en;q=0.5"

Firefox does this even though intl.accept_languages is by default set to "pl, en-US, en" and settings look alright in GUI ("Content" page).

Looks like this value is ignored until Firefox "thinks" it was set by user manually (value's status changes from "default" to "user's" in about:config).

The workaround is to double click intl.accept_languages value in about:config and click "OK" button without changing anything.

[Launchpad Janitor (janitor)]

Status changed to 'Confirmed' because the bug affects multiple users.

[Dmitry Nurislamov (nimms)]

The same issue, and it's not Ubuntu-specific.

The reason is that Firefox does not write `intl.accept_languages`
value to the new profile's `prefs.js`.

After creating a new profile, the first launch is nice and dandy:
websites are in Russian, as I expect. But after I close Firefox
and open it again, they turn English.

The language priority is correct in GUI, but it's missing from `prefs.js`.
To fix this behavior, I go to GUI settings, put the first language down,
then put it back to top and click "OK". Just clicking the button
without changing the order doesn't help.

To reproduce the bug, create a new Firefox profile, launch Firefox with it,
*exit and launch again*. Then go to e.g. https://www.debian.org/
It should be in English instead of your system language.
Check the profile's `prefs.js` to make sure there's no
`intl.accept_languages` in it.

Now do the above priority change thing and refresh the page. It should be
in your language now. Check the `prefs.js` again, the setting
should be there.

[Paweł Kowalik (pkowalik)]

I can confirm that this bug still exists in firefox 59.0.2+build1-0ubuntu0.16.04.3. Workaround provided in #2 solves the problem.

OS: Xubuntu 16.04.4 x64

[Wes (wesinator)]

Same problem on Bionic 61.0.1+build1-0ubuntu0.18.04.1

intl.accept_languages default value is "en-US, en", but Accept-Language header is "en-GB,en"
Websites seem to give the British language version even though the locale is US