wireshark: export QT_PLUGIN_PATH in shellHook

[teto]

...else program fails with:
This application failed to start because it could not find or load the Qt platform plugin "xcb"
in "".

Motivation for this change

I am fixing a bug in wireshark within a nix-shell and could not start the dev wireshark due to this error.

Things done

• Tested using sandboxing (nix.useSandbox on NixOS, or option 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/)
• Determined the impact on package closure size (by running nix path-info -S before and after)
• Fits CONTRIBUTING.md.

---

[GrahamcOfBorg]

Success on x86_64-linux (full log)

Attempted: wireshark

Partial log (click to expand)

shrinking /nix/store/pflpji81p8gdm5x2pa7mzvgiq4scav7x-wireshark-qt-2.6.1/lib/wireshark/extcap/randpktdump
shrinking /nix/store/pflpji81p8gdm5x2pa7mzvgiq4scav7x-wireshark-qt-2.6.1/lib/wireshark/extcap/sshdump
shrinking /nix/store/pflpji81p8gdm5x2pa7mzvgiq4scav7x-wireshark-qt-2.6.1/lib/libwireshark.so.11.0.1
shrinking /nix/store/pflpji81p8gdm5x2pa7mzvgiq4scav7x-wireshark-qt-2.6.1/lib/libwscodecs.so.0.0.0
gzipping man pages under /nix/store/pflpji81p8gdm5x2pa7mzvgiq4scav7x-wireshark-qt-2.6.1/share/man/
strip is /nix/store/4qvrxzxa535y8304mk195x50b6p9607d-binutils-2.30/bin/strip
stripping (with command strip and flags -S) in /nix/store/pflpji81p8gdm5x2pa7mzvgiq4scav7x-wireshark-qt-2.6.1/lib  /nix/store/pflpji81p8gdm5x2pa7mzvgiq4scav7x-wireshark-qt-2.6.1/bin
patching script interpreter paths in /nix/store/pflpji81p8gdm5x2pa7mzvgiq4scav7x-wireshark-qt-2.6.1
checking for references to /build in /nix/store/pflpji81p8gdm5x2pa7mzvgiq4scav7x-wireshark-qt-2.6.1...
postPatchMkspecs

[GrahamcOfBorg]

Success on aarch64-linux (full log)

Attempted: wireshark

Partial log (click to expand)

shrinking /nix/store/b5yycqxv897bdhvzpycp2rchvzybc666-wireshark-qt-2.6.1/bin/sharkd
shrinking /nix/store/b5yycqxv897bdhvzpycp2rchvzybc666-wireshark-qt-2.6.1/bin/rawshark
shrinking /nix/store/b5yycqxv897bdhvzpycp2rchvzybc666-wireshark-qt-2.6.1/bin/tshark
gzipping man pages under /nix/store/b5yycqxv897bdhvzpycp2rchvzybc666-wireshark-qt-2.6.1/share/man/
strip is /nix/store/0pjsgkxz0rp5baycq5sp2s72lrr5q9sg-binutils-2.30/bin/strip
stripping (with command strip and flags -S) in /nix/store/b5yycqxv897bdhvzpycp2rchvzybc666-wireshark-qt-2.6.1/lib  /nix/store/b5yycqxv897bdhvzpycp2rchvzybc666-wireshark-qt-2.6.1/bin
patching script interpreter paths in /nix/store/b5yycqxv897bdhvzpycp2rchvzybc666-wireshark-qt-2.6.1
checking for references to /build in /nix/store/b5yycqxv897bdhvzpycp2rchvzybc666-wireshark-qt-2.6.1...
postPatchMkspecs
/nix/store/b5yycqxv897bdhvzpycp2rchvzybc666-wireshark-qt-2.6.1

[orivej]

This issue is not specific to Wireshark, it is common to all Qt packages: you need ${qt5.qtbase}/bin (or the directory where it is installed, e.g. /run/current-system/sw/bin or ~/.nix-profile/bin) in your PATH for Qt to find its plugins. Does nix-shell -p qt5.qtbase wireshark work?

[matthewbauer]

Ok this appears to be related to my issue: #42893

I didn't realize that qt apps needed qtbase installed. Can we provide a fallback path in these cases? IMO relying on propagatedUserEnvPkgs to do the right thing is harmful because not everyone will install your app through the traditional nix-env -i method.

[teto]

@orivej what if qtbase/wireshark is not installed ? Installed wireshark works without any problem but I am doing some development on it, thus I would like build/run/wireshark to work without having to specify manually in nix-shell the correct paths.

[orivej]

@teto You only have to make sure that qtbase is in your PATH. If your nix-shell is not --pure, the PATH should be inherited from your shell, so you won't have to change it inside nix-shell. Make sure that nix-shell uses the same revision of Nixpkgs from which you have installed qtbase, otherwise plugins for that version of Qt may not be available or may fail to load. (You don't have to explicitly install qtbase as long as you install any application that depends on it, because it is a propagatedUserEnvPkgs package.) See also #42893 (comment).

[jtojnar]

If we wanted to add this, it should probably be conditional on withQt.

[matthewbauer]

I think a makeWrapper call adding QT_PLUGIN_PATH around $out/bin/wireshark makes more sense here.

[teto]

@matthewbauer it is already wrapped. I am specifically targeting the developing phase when you are in your $ nix-shell -A wireshark and want to run the build/run/wiresahrk binary (i.e., no installPhase, no wrapper). Or do you mean it should be wrapped as a postBuild hook ? that would work too

[matthewbauer]

Ok that seems like something we can do in the qt hook becuase it should apply to all qt based packages.

Mistake

[teto]

seems like more holistic solutions are coming up. closing