fix on setting the proper completions and sets the shell

modules/fish.nix

@@ -1,12 +1,13 @@
 { config, pkgs, lib, ... }:
-
 let
   fish-rust = pkgs.callPackage ../pkgs/fish-rust { };
 in
 {
-  programs.fish.enable = true;
+  programs.fish = {
+    enable = true;
+    package = fish-rust;
+  };
   environment.systemPackages = with pkgs; [
-    fish-rust
     starship
     fzf
     bat
@@ -14,4 +15,5 @@ in
     fd
     ripgrep
   ];
+  users.users.cobray.shell = lib.mkForce fish-rust;
 }

pkgs/fish-rust/default.nix

@@ -1,16 +1,13 @@
-{ lib, rustPlatform, fetchgit, pkg-config, cmake, ncurses, sphinx }:
-
+{ lib, rustPlatform, fetchgit, ncurses, sphinx, python3 }:
 rustPlatform.buildRustPackage rec {
   pname = "fish";
-  version = "unstable-2025-03-14";
-
+  version = "4.1-2025-03-14";
   src = fetchgit {
     url = "https://github.com/fish-shell/fish-shell.git";
     rev = "refs/heads/master";
     fetchSubmodules = true;
     sha256 = "18zpwa3yddic6wdwj7g51w6n4apwsixfvl179yddk2nwfpxhv4hq";
   };
-
   cargoLock = {
     lockFile = "${src}/Cargo.lock";
     outputHashes = {
@@ -18,21 +15,32 @@ rustPlatform.buildRustPackage rec {
       "pcre2-sys-0.2.9" = "0mhjw7fvrzxb3fd0c534a17qgy6svz0z8269d2fs6q8aw11610mr";
     };
   };
-
-  nativeBuildInputs = [ pkg-config cmake sphinx ];
   buildInputs = [ ncurses ];
-
+  nativeBuildInputs = [ sphinx python3 ];
   preBuild = ''
     export FISH_BUILD_VERSION="${version}"
     export FISH_BUILD_DOCS=1
   '';
-
+  postInstall = ''
+    export HOME=$(mktemp -d)
+    mkdir -p $HOME/.local/share/fish/install
+    $out/bin/fish --install
+    mkdir -p $out/share/fish
+    cp -r $HOME/.local/share/fish/install/* $out/share/fish/ 2>/dev/null || true
+    mkdir -p $out/share/fish/tools
+    cp $src/share/tools/create_manpage_completions.py $out/share/fish/tools/
+    cp $src/share/tools/deroff.py $out/share/fish/tools/
+    chmod +x $out/share/fish/tools/create_manpage_completions.py
+    chmod +x $out/share/fish/tools/deroff.py
+    rm -rf $HOME
+  '';
   doCheck = false;
-
   meta = with lib; {
     description = "The user-friendly command line shell (Rust version)";
     homepage = "https://fishshell.com/";
     license = licenses.gpl2;
     platforms = platforms.unix;
+    mainProgram = "fish";
   };
+  passthru.shellPath = "/bin/fish";
 }