From aaa2e9705ab1bcfebc14f598ae60237749e75033 Mon Sep 17 00:00:00 2001
From: Charles Strahan <charles.c.strahan@gmail.com>
Date: Wed, 14 Jan 2015 04:20:50 -0500
Subject: [PATCH] ruby: cache gem files

---
 pkgs/development/interpreters/ruby/gem.nix | 8 ++++++++
 1 file changed, 8 insertions(+)

diff --git a/pkgs/development/interpreters/ruby/gem.nix b/pkgs/development/interpreters/ruby/gem.nix
index 084d0fdb466..ec263d568b8 100644
--- a/pkgs/development/interpreters/ruby/gem.nix
+++ b/pkgs/development/interpreters/ruby/gem.nix
@@ -113,6 +113,14 @@ stdenv.mkDerivation (attrs // {
     fi
     EOF
 
+    # Copy the gem file to the cache.
+    # This is very important in order for many parts of Bundler to not blow up.
+    # See https://github.com/bundler/bundler/issues/3327
+    gemname=$(basename $out/${ruby.gemPath}/gems/*).gem
+    echo "caching $gemname"
+    mkdir $out/${ruby.gemPath}/cache
+    cp $gempkg $out/${ruby.gemPath}/cache/$gemname
+
     runHook postInstall
   '';