1 files changed, 15 insertions, 0 deletions
diff --git a/pkgs/development/haskell-modules/lib.nix b/pkgs/development/haskell-modules/lib.nix
index f4ebe549c502..942163ea2096 100644
--- a/pkgs/development/haskell-modules/lib.nix
+++ b/pkgs/development/haskell-modules/lib.nix
@@ -354,4 +354,19 @@ rec {
 
       in
         builtins.listToAttrs (map toKeyVal haskellPaths);
+
+  # Modify a Haskell package to add completion scripts for the given executable
+  # produced by it. These completion scripts will be picked up automatically if
+  # the resulting derivation is installed, e.g. by `nix-env -i`.
+  addOptparseApplicativeCompletionScripts = exeName: pkg: overrideCabal pkg (drv: {
+    postInstall = (drv.postInstall or "") + ''
+      bashCompDir="$out/share/bash-completion/completions"
+      zshCompDir="$out/share/zsh/vendor-completions"
+      fishCompDir="$out/share/fish/vendor_completions.d"
+      mkdir -p "$bashCompDir" "$zshCompDir" "$fishCompDir"
+      "$out/bin/${exeName}" --bash-completion-script "$out/bin/${exeName}" >"$bashCompDir/${exeName}"
+      "$out/bin/${exeName}" --zsh-completion-script "$out/bin/${exeName}" >"$zshCompDir/_${exeName}"
+      "$out/bin/${exeName}" --fish-completion-script "$out/bin/${exeName}" >"$fishCompDir/${exeName}.fish"
+    '';
+  });
 }