firefox: support for native messaging hosts in wrapper

[roastiek]

Motivation for this change

New web extensions sometimes need native binaries installed to work. However in firefox the search path for these binaries is hardcoded to /usr/lib/mozilla/native-messaging-hosts.
I added small patch that allows overriding that path by new env varibale MOZ_SYSTEM_DIR and enhanced the wrapper. Here is an example integration of chrome-gnome-shell.
This will allows to add existing native messaging hosts (#28882 and #24803) to firefox in similar way like plugins .

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option build-use-sandbox in nix.conf on non-NixOS)
• Built on platform(s)
  • NixOS
  • macOS
  • other Linux distributions
• Tested via one or more NixOS test(s) if existing and applicable for the change (look inside nixos/tests)
• Tested compilation of all pkgs that depend on this change using nix-shell -p nox --run "nox-review wip"
• Tested execution of all binary files (usually in ./result/bin/)
• Fits CONTRIBUTING.md.

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[eqyiel]

Thanks for working on this, this will help packages like browserpass (which has a NixOS module) and friends.

@deedrah is MOZ_SYSTEM_DIR documented anywhere or is it a name that you made up?

[eqyiel]

My bad, I read the patch. I wonder if this is something that can be achieved using a FHS user env wrapper in order to avoid recompiling?

[7c6f434c]

@eqyiel not sure if a rebuild is worse than requiring user namespaces on non-NixOS Linux in this case

Given that Firefox 57 (with Big Changes™) is expected this week, if we check the patch with the new version first, most users won't even get an extra rebuild.

[eqyiel]

@7c6f434c that's true, I didn't even consider that. In any case I will be happy to be able to use native messaging hosts in NixOS!

[7c6f434c]

@taku0 any opinion (as recently you are the person who usually updates Firefox)? Also, any opinion about trying to combine this with FF57 update?

[taku0]

@7c6f434c It looks good to me. I don't care rebuilding, but if it is not desirable, I will make FF57 branch on this branch.
@deedrah If this is merged, would you send it also to the upstream for the sake of firefox-bin?

[taku0]

Here is a WIP FF57 branch (without this PR): https://github.com/taku0/nixpkgs/tree/firefox-bin-57.0

[7c6f434c]

@taku0 I think rebuilding is fine if the two rebuilds are close; do as is more convenient. I just meant that all the events would be relatively close to each other.

[7c6f434c]

Wait a minute, the release source tarball is already available?

[roastiek]

Hmm, maybe I have found another way. Most of the code of native messaging is written in JavaScript and theoretically it should be possible to change it in the wrapper. I known where and what to change but I have problems with repacking omni.ja.

[taku0]

I succeeded to build Firefox 57 with this patch without errors.

I made PR for Firefox 57, without this patch.
#31661

[7c6f434c]

Double merge and a hope for the best.

[roastiek]

Nice.

I will prepare cleaner version of the patch for firefox. Instead of overriding system dir, it will extend search path for native mess. hosts as MOZ_PLUGIN_PATH for plugins. It should have higher chance to get merged into the upstream. And if not, I have working proof of concept patching omni.ja in the firefox wrapper only.