bundlerEnv: Add option to copy gem files instead of symlinking

The way ruby loads gems and keeps track of their paths seems to not
always work very well when the gems are accessed through
symlinks. Ruby will then complain that the same files are loaded
multiple times; it relies on the file's full path to determine whether
the file is loaded or not.

This adds an option to simply copy all gem files into the environment
instead, which gets rid of this issue, but may instead result in major
file duplication.

(cherry-picked from commit affcf9ba1e)

pkgs/development/ruby-modules/bundled-common/default.nix

@@ -1,4 +1,4 @@
-{ stdenv, runCommand, ruby, lib
+{ stdenv, runCommand, ruby, lib, rsync
 , defaultGemConfig, buildRubyGem, buildEnv
 , makeWrapper
 , bundler
@@ -13,6 +13,7 @@
 , lockfile ? null
 , gemset ? null
 , ruby ? defs.ruby
+, copyGemFiles ? false # Copy gem files instead of symlinking
 , gemConfig ? defaultGemConfig
 , postBuild ? null
 , document ? []
@@ -96,7 +97,8 @@ let
 
   envPaths = lib.attrValues gems ++ lib.optional (!hasBundler) bundler;
 
-  basicEnv = buildEnv {
+
+  basicEnvArgs = {
     inherit buildInputs ignoreCollisions;
 
     name = name';
@@ -154,5 +156,17 @@ let
         };
     };
   };
+
+  basicEnv =
+    if copyGemFiles then
+      runCommand name' basicEnvArgs ''
+        mkdir -p $out
+        for i in $paths; do
+          ${rsync}/bin/rsync -a $i/lib $out/
+        done
+        eval "$postBuild"
+      ''
+    else
+      buildEnv basicEnvArgs;
 in
   basicEnv

pkgs/development/ruby-modules/bundler-env/default.nix

@@ -1,4 +1,6 @@
-{ ruby, lib, callPackage, defaultGemConfig, buildEnv, bundler }@defs:
+{ ruby, lib, callPackage, defaultGemConfig, buildEnv, runCommand
+, bundler, rsync
+}@defs:
 
 { name ? null
 , pname ? null
@@ -8,6 +10,7 @@
 , gemset ? null
 , groups ? ["default"]
 , ruby ? defs.ruby
+, copyGemFiles ? false # Copy gem files instead of symlinking
 , gemConfig ? defaultGemConfig
 , postBuild ? null
 , document ? []
@@ -38,23 +41,35 @@ in
   if pname == null then
     basicEnv // { inherit name basicEnv; }
   else
-    (buildEnv {
-      inherit ignoreCollisions;
+    let
+      bundlerEnvArgs = {
+        inherit ignoreCollisions;
 
-      name = basicEnv.name;
+        name = basicEnv.name;
 
-      paths = envPaths;
-      pathsToLink = [ "/lib" ];
+        paths = envPaths;
+        pathsToLink = [ "/lib" ];
 
-      postBuild = genStubsScript {
-        inherit lib ruby bundler groups;
-        confFiles = basicEnv.confFiles;
-        binPaths = [ basicEnv.gems.${pname} ];
-      } + lib.optionalString (postBuild != null) postBuild;
+        postBuild = genStubsScript {
+          inherit lib ruby bundler groups;
+          confFiles = basicEnv.confFiles;
+          binPaths = [ basicEnv.gems.${pname} ];
+        } + lib.optionalString (postBuild != null) postBuild;
 
-      meta = { platforms = ruby.meta.platforms; } // meta;
-      passthru = basicEnv.passthru // {
-        inherit basicEnv;
-        inherit (basicEnv) env;
-      } // passthru;
-    })
+        meta = { platforms = ruby.meta.platforms; } // meta;
+        passthru = basicEnv.passthru // {
+          inherit basicEnv;
+          inherit (basicEnv) env;
+        } // passthru;
+      };
+    in
+      if copyGemFiles then
+        runCommand basicEnv.name bundlerEnvArgs ''
+          mkdir -p $out
+          for i in $paths; do
+            ${rsync}/bin/rsync -a $i/lib $out/
+          done
+          eval "$postBuild"
+        ''
+      else
+        buildEnv bundlerEnvArgs