From c34f5176f1173ac2cdaeed4512a61389d98f9d9f Mon Sep 17 00:00:00 2001
From: John Ericson <John.Ericson@Obsidian.Systems>
Date: Tue, 30 Oct 2018 14:20:24 -0400
Subject: [PATCH] haskell-lib: Factor out shell completion scripts helper

---
 pkgs/development/haskell-modules/lib.nix | 15 +++++++++++++++
 pkgs/top-level/all-packages.nix          | 10 +++-------
 2 files changed, 18 insertions(+), 7 deletions(-)

diff --git a/pkgs/development/haskell-modules/lib.nix b/pkgs/development/haskell-modules/lib.nix
index 8dae7c8d72c..10edf69478b 100644
--- a/pkgs/development/haskell-modules/lib.nix
+++ b/pkgs/development/haskell-modules/lib.nix
@@ -407,4 +407,19 @@ 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"
+    '';
+  });
 }
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index a2152113ae5..abd7db6263d 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -1001,10 +1001,10 @@ with pkgs;
 
   cue2pops = callPackage ../tools/cd-dvd/cue2pops { };
 
-  cabal2nix = haskell.lib.overrideCabal haskellPackages.cabal2nix (drv: {
+  cabal2nix = haskell.lib.overrideCabal (haskell.lib.addOptparseApplicativeCompletionScripts "cabal2nix" haskellPackages.cabal2nix) (drv: {
     isLibrary = false;
     enableSharedExecutables = false;
-    executableToolDepends = [ makeWrapper ];
+    executableToolDepends = (drv.executableToolDepends or []) ++ [ makeWrapper ];
     postInstall = ''
       exe=$out/libexec/${drv.pname}-${drv.version}/${drv.pname}
       install -D $out/bin/${drv.pname} $exe
@@ -1012,11 +1012,7 @@ with pkgs;
       makeWrapper $exe $out/bin/${drv.pname} \
         --prefix PATH ":" "${nix}/bin" \
         --prefix PATH ":" "${nix-prefetch-scripts}/bin"
-      mkdir -p $out/share/{bash-completion/completions,zsh/vendor-completions,fish/completions}
-      $exe --bash-completion-script $exe >$out/share/bash-completion/completions/${drv.pname}
-      $exe --zsh-completion-script $exe >$out/share/zsh/vendor-completions/_${drv.pname}
-      $exe --fish-completion-script $exe >$out/share/fish/completions/${drv.pname}.fish
-    '';
+    '' + (drv.postInstall or "");
   });
 
   stack2nix = with haskell.lib; overrideCabal (justStaticExecutables haskellPackages.stack2nix) (drv: {