1 files changed, 24 insertions, 8 deletions
diff --git a/nixpkgs/nixos/modules/programs/fish.nix b/nixpkgs/nixos/modules/programs/fish.nix
index 03d6c26c8c87..bcb5a3f341b5 100644
--- a/nixpkgs/nixos/modules/programs/fish.nix
+++ b/nixpkgs/nixos/modules/programs/fish.nix
@@ -172,7 +172,7 @@ in
     programs.fish.interactiveShellInit = ''
       # add completions generated by NixOS to $fish_complete_path
       begin
-        # joins with null byte to acommodate all characters in paths, then respectively gets all paths before / after the first one including "generated_completions",
+        # joins with null byte to acommodate all characters in paths, then respectively gets all paths before (exclusive) / after (inclusive) the first one including "generated_completions",
         # splits by null byte, and then removes all empty lines produced by using 'string'
         set -l prev (string join0 $fish_complete_path | string match --regex "^.*?(?=\x00[^\x00]*generated_completions.*)" | string split0 | string match -er ".")
         set -l post (string join0 $fish_complete_path | string match --regex "[^\x00]*generated_completions.*" | string split0 | string match -er ".")
@@ -182,13 +182,28 @@ in
 
     environment.etc."fish/generated_completions".source =
       let
+        patchedGenerator = pkgs.stdenv.mkDerivation {
+          name = "fish_patched-completion-generator";
+          srcs = [
+            "${pkgs.fish}/share/fish/tools/create_manpage_completions.py"
+            "${pkgs.fish}/share/fish/tools/deroff.py"
+          ];
+          unpackCmd = "cp $curSrc $(basename $curSrc)";
+          sourceRoot = ".";
+          patches = [ ./fish_completion-generator.patch ]; # to prevent collisions of identical completion files
+          dontBuild = true;
+          installPhase = ''
+            mkdir -p $out
+            cp * $out/
+          '';
+          preferLocalBuild = true;
+          allowSubstitutes = false;
+        };
         generateCompletions = package: pkgs.runCommand
-          "${package.name}-fish-completions"
+          "${package.name}_fish-completions"
           (
             {
-              src = package;
-              nativeBuildInputs = [ pkgs.python3 ];
-              buildInputs = [ pkgs.fish ];
+              inherit package;
               preferLocalBuild = true;
               allowSubstitutes = false;
             }
@@ -196,13 +211,14 @@ in
           )
           ''
             mkdir -p $out
-            if [ -d $src/share/man ]; then
-              find $src/share/man -type f | xargs python ${pkgs.fish}/share/fish/tools/create_manpage_completions.py --directory $out >/dev/null
+            if [ -d $package/share/man ]; then
+              find $package/share/man -type f | xargs ${pkgs.python3.interpreter} ${patchedGenerator}/create_manpage_completions.py --directory $out >/dev/null
             fi
           '';
       in
         pkgs.buildEnv {
-          name = "system-fish-completions";
+          name = "system_fish-completions";
+          ignoreCollisions = true;
           paths = map generateCompletions config.environment.systemPackages;
         };