zsh: fix trailing slash breaking zshenv

[Buttars]

Description

If a user has a trailing / in their user.users.<user>.home value with the zsh enabled the module fails to properly check the equality of dotDir and the home path.

The libs.nix module is stripping the trailing / from the dotDirAbs and dotDirRel and not for homeDir.

You can see the how the values are evaluated by running this script:

nix eval --json --impure --expr '
let
  flake   = builtins.getFlake ("path:" + toString ./.);
  libPkgs = if flake.inputs ? nixpkgs then flake.inputs.nixpkgs.lib else import <nixpkgs/lib> {};
  user    = builtins.getEnv "USER";
  host    = builtins.getEnv "HOSTNAME";

  hmCfg =
    if flake ? darwinConfigurations then
      let
        dcs = flake.darwinConfigurations;
        machineKey =
          if host != "" && builtins.hasAttr host dcs
          then host
          else builtins.head (builtins.attrNames dcs);
        hmUsers = dcs.${machineKey}.config.home-manager.users;
      in
        if builtins.hasAttr user hmUsers
        then hmUsers.${user}
        else throw "User ${user} not found in home-manager.users for ${machineKey}"
    else
      let
        hcs = flake.homeConfigurations;
        keys = builtins.attrNames hcs;
        matches = builtins.filter (k: (hcs.${k}.config.home.username or "") == user) keys;
        key = if matches != [] then builtins.head matches else builtins.head keys;
      in
        hcs.${key}.config;

  hmSrc = flake.inputs.home-manager.outPath;
  vals  = import (hmSrc + "/modules/programs/zsh/lib.nix") { config = hmCfg; lib = libPkgs; };
in { inherit (vals) homeDir dotDirAbs dotDirRel; }
' | jq

@lzpreslav actually mentioned this on the PR a few months back.
#6089 (comment)

Relevant LOC:
https://github.com/nix-community/home-manager/blob/master/modules/programs/zsh/lib.nix#L6
https://github.com/nix-community/home-manager/blob/master/modules/programs/zsh/lib.nix#L69
https://github.com/nix-community/home-manager/blob/master/modules/programs/zsh/lib.nix#L99-L100
https://github.com/nix-community/home-manager/blob/master/modules/programs/zsh/default.nix#L415

Checklist

• Change is backwards compatible.

• Code formatted with nix fmt or
  nix-shell -p treefmt nixfmt deadnix keep-sorted --run treefmt.

• Code tested through nix run .#tests -- test-all or
  nix-shell --pure tests -A run.all.

• Test cases updated/added. See example.

• Commit messages are formatted like

  {component}: {description}
  
  {long description}
  

  See CONTRIBUTING for more information and recent commit messages for examples.

[Buttars]

If someone could guide me on writing tests for this I would appreciate it. I only see tests testing the output of the module and not any unit tests.

[Buttars]

@khaneliman

[stale]

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[khaneliman]

Could you possibly add a test case for this?

[khaneliman]

Nvm just realized I missed this PR a while ago and you had a comment about not knowing how to.

[Buttars]

Thanks for getting back to me on this. I'd happily add test cases if you could point me to an example or documentation. Let me know if you'd still like to get this merged. 😁

I tried looking for other examples and documentation but couldn't figure it out.

[khaneliman]

I was playing around with tests and found some other cases to solve for. Just gonna push to a new branch and can you verify it works for you.

[khaneliman]

@Buttars can you test #8378 it should work