Bug compiling using Agda when Unicode ⟨⟩ is in file system

[guilhermehas]

Describe the bug

Agda can't compile files their names have Unicode ⟨⟩ on them.

Steps To Reproduce

Just run nix build in this file:

{
  description = "Agda bug";

  inputs.nixpkgs.url = github:NixOS/nixpkgs/nixos-21.11;

  outputs = { self, nixpkgs }:
    let system = "x86_64-linux";
        pkgs = import nixpkgs { inherit system; };
        unicode = "⟨⟩";
    in {
      defaultPackage.x86_64-linux = with pkgs;
        stdenv.mkDerivation {
          name = "Agda-bug";
          src = ./.;
          buildInputs = [ agda ];
          buildPhase = ''
            cat >> Everything.agda <<EOF
            import ${unicode}
            EOF
            touch ${unicode}.agda
            ls
            cat Everything.agda
            agda Everything.agda
          '';
          installPhase = ''touch $out && cat Everything.agda >> $out && ls >> $out'';
        };
    };
}

Expected behavior

It should compile like in this file:
https://github.com/agda/cubical/blob/master/Cubical/Syntax/%E2%9F%A8%E2%9F%A9.agda

Notify maintainers

@abbradar @Ericson2314 @turion @alexarice @neosimsim @Fuuzetsu @zimbatm @AndersonTorres @roberth @TilCreator @globin

[user@system:~]$ nix build
error: builder for '/nix/store/hqqf7c9lkjs0ip9ps1rd86i6xjc1bmxw-Agda-bug.drv' failed with exit code 42;
       last 10 log lines:
       > source root is 0c6bpyd78b0pgy7hm869jwdwk5jhd9si-source
       > patching sources
       > configuring
       > no configure script, doing nothing
       > building
       >  Everything.agda   flake.lock   flake.nix  ''$'\342\237\250\342\237\251''.agda'
       > import ⟨⟩
       > Checking Everything (/build/0c6bpyd78b0pgy7hm869jwdwk5jhd9si-source/Everything.agda).
       > /build/0c6bpyd78b0pgy7hm869jwdwk5jhd9si-source/Everything.agda:1,1-10
       > Failed to find source of module
       For full logs, run 'nix log /nix/store/hqqf7c9lkjs0ip9ps1rd86i6xjc1bmxw-Agda-bug.drv'.

[alexarice]

Does this compile on a non nix agda?

[guilhermehas]

Does this compile on a non nix agda?

It compiles like in this file:
https://github.com/agda/cubical/blob/master/Cubical/Syntax/%E2%9F%A8%E2%9F%A9.agda

[ncfavier]

Fix: export LANG=C.UTF-8. I wonder if that should be done by default somewhere.

[guilhermehas]

Fix: export LANG=C.UTF-8. I wonder if that should be done by default somewhere.

It worked here, but I will let it open because it is already not fixed in Agda or in something inside nixpkgs (such as mkDerivation).

[alexarice]

Out of interest, we already have this flag set for the cubical derivation

nixpkgs/pkgs/development/libraries/agda/cubical/default.nix

Line 14 in 73feaed

LC_ALL = "en_US.UTF-8";

Perhaps it should be default for agda, would there be any downside to this?

[ncfavier]

Opened agda/agda#5903

[AndersonTorres]

Related: agda/agda#4678

[iblech]

Perhaps it should be default for agda, would there be any downside to this?

I agree and will prepare a pull request. This comes up when updating to Agda 2.6.3, the stdlib doesn't compile without it.