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fish-manpage-completions-fix

Overlays

A one-line nixpkgs overlay that restores create_manpage_completions.py on disk so home-manager's programs.fish completion generator keeps working against fish 4.8+.

The problem

fish 4.8 stopped shipping share/fish/tools/ on disk. The manpage-completions generator, create_manpage_completions.py, is now embedded in the fish binary and extracted on demand rather than living as a file in the package.

home-manager's fish module hasn't caught up (in released channels). When programs.fish.generateCompletions is enabled, home-manager still invokes:

${fish}/share/fish/tools/create_manpage_completions.py

That path no longer exists, so every <pkg>-fish-completions derivation fails to build — e.g. the first thing that breaks is often a package like bat whose completions home-manager tries to generate.

The fix / key insight

fish exposes its embedded files through status get-file. home-manager's development branch already extracts the generator this way; this overlay does the same thing eagerly at package build time so the on-disk path exists again:

$out/bin/fish --no-config \
  -c 'status get-file tools/create_manpage_completions.py' \
  > $out/share/fish/tools/create_manpage_completions.py

The if [ ! -e ... ] guard makes it a no-op on older/newer fish versions that already ship (or re-ship) the file — so it is safe to leave in place across upgrades.

Usage

Add the overlay to nixpkgs:

nixpkgs.overlays = [ (import ./fish-manpage-completions-fix) ];

or, with flakes:

pkgs = import nixpkgs {
  inherit system;
  overlays = [ (import ./fish-manpage-completions-fix) ];
};

No options — it patches pkgs.fish in place.

Alternatives / caveats

  • Prefer disabling the generator if you can. fish ships real, curated completions for common tools anyway, so setting programs.fish.generateCompletions = false; loses little and avoids the whole issue. Use this overlay when you specifically want home-manager to keep generating manpage-derived completions.
  • This is a stopgap. Once your home-manager input carries the upstream fix (extracting the generator via status get-file itself), remove the overlay — the guard means keeping it around is harmless but unnecessary.
  • Only affects pkgs.fish. If some other package pins its own fish, override that one too.

Source

overlays/fish-manpage-completions-fix/default.nix 
# fish 4.8 stopped shipping share/fish/tools/ on disk — the manpage-completions
# generator (create_manpage_completions.py) is now embedded in the fish binary.
# home-manager's fish module still invokes
#   ${fish}/share/fish/tools/create_manpage_completions.py
# for programs.fish generateCompletions, so every *-fish-completions derivation
# fails to build against fish 4.8+.
#
# This overlay re-materializes the script from the binary via `status get-file`
# (the same mechanism home-manager master uses to extract it). Drop the overlay
# once your home-manager input carries that fix.
#
# Usage — add to nixpkgs.overlays:
#   nixpkgs.overlays = [ (import ./fish-manpage-completions-fix) ];
#
# or with flakes:
#   pkgs = import nixpkgs { overlays = [ (import ./fish-manpage-completions-fix) ]; };
_: prev: {
  fish = prev.fish.overrideAttrs (old: {
    postInstall = (old.postInstall or "") + ''
      if [ ! -e $out/share/fish/tools/create_manpage_completions.py ]; then
        mkdir -p $out/share/fish/tools
        $out/bin/fish --no-config \
          -c 'status get-file tools/create_manpage_completions.py' \
          > $out/share/fish/tools/create_manpage_completions.py
      fi
    '';
  });
}