ruby: fix build with bundled gems

pkgs/development/interpreters/ruby/default.nix

@@ -103,16 +103,21 @@ let
           }).${ver.majMinTiny}
           ++ op (lib.versionOlder ver.majMin "3.1") ./do-not-regenerate-revision.h.patch
           ++ op (atLeast30 && useBaseRuby) ./do-not-update-gems-baseruby.patch
-          # Ruby prior to 3.0 has a bug the installer (tools/rbinstall.rb) but
-          # the resulting error was swallowed. Newer rubygems no longer swallows
-          # this error. We upgrade rubygems when rubygemsSupport is enabled, so
-          # we have to fix this bug to prevent the install step from failing.
-          # See https://github.com/ruby/ruby/pull/2930
-          ++ op (!atLeast30 && rubygemsSupport)
+          ++ ops (!atLeast30 && rubygemsSupport) [
+            # We upgrade rubygems to a version that isn't compatible with the
+            # ruby 2.7 installer. Backport the upstream fix.
+            ./rbinstall-new-rubygems-compat.patch
+
+            # Ruby prior to 3.0 has a bug the installer (tools/rbinstall.rb) but
+            # the resulting error was swallowed. Newer rubygems no longer swallows
+            # this error. We upgrade rubygems when rubygemsSupport is enabled, so
+            # we have to fix this bug to prevent the install step from failing.
+            # See https://github.com/ruby/ruby/pull/2930
             (fetchpatch {
               url = "https://github.com/ruby/ruby/commit/261d8dd20afd26feb05f00a560abd99227269c1c.patch";
               sha256 = "0wrii25cxcz2v8bgkrf7ibcanjlxwclzhayin578bf0qydxdm9qy";
-            });
+            })
+          ];
 
         postUnpack = opString rubygemsSupport ''
           rm -rf $sourceRoot/{lib,test}/rubygems*
@@ -189,6 +194,11 @@ let
               sed -i '/CC_VERSION_MESSAGE/d' $rbConfig
             ''
           }
+          # Remove unnecessary external intermediate files created by gems
+          extMakefiles=$(find $out/lib/ruby/gems -name Makefile)
+          for makefile in $extMakefiles; do
+            make -C "$(dirname "$makefile")" distclean
+          done
           # Bundler tries to create this directory
           mkdir -p $out/nix-support
           cat > $out/nix-support/setup-hook <<EOF

pkgs/development/interpreters/ruby/rbinstall-new-rubygems-compat.patch

@@ -0,0 +1,87 @@
+From 8e85d27f9ccfe152fc1b891c19f125915a907493 Mon Sep 17 00:00:00 2001
+From: =?UTF-8?q?V=C3=ADt=20Ondruch?= <vondruch@redhat.com>
+Date: Tue, 1 Oct 2019 12:03:33 +0200
+Subject: [PATCH] Use `Gem::Package` like object instead of monkey patching.
+
+1. This is similar to what RubyGems does and it is less magic [[1]].
+2. It avoids deprecated code paths in RubyGems [[2]].
+
+[1]: https://github.com/rubygems/rubygems/blob/92892bbc3adba86a90756c385433835f6761b8da/lib/rubygems/installer.rb#L151
+[2]: https://github.com/rubygems/rubygems/blob/92892bbc3adba86a90756c385433835f6761b8da/lib/rubygems/installer.rb#L187
+
+(cherry picked from commit e960ef6f18a25c637c54f00c75bb6c24f8ab55d0)
+---
+ tool/rbinstall.rb | 47 +++++++++++++++++++++++++++--------------------
+ 1 file changed, 27 insertions(+), 20 deletions(-)
+
+diff --git a/tool/rbinstall.rb b/tool/rbinstall.rb
+index 060390626f..28ae8c409a 100755
+--- a/tool/rbinstall.rb
++++ b/tool/rbinstall.rb
+@@ -710,28 +710,34 @@ def remove_prefix(prefix, string)
+     end
+   end
+ 
+-  class UnpackedInstaller < Gem::Installer
+-    module DirPackage
+-      def extract_files(destination_dir, pattern = "*")
+-        path = File.dirname(@gem.path)
+-        return if path == destination_dir
+-        File.chmod(0700, destination_dir)
+-        mode = pattern == "bin/*" ? $script_mode : $data_mode
+-        spec.files.each do |f|
+-          src = File.join(path, f)
+-          dest = File.join(without_destdir(destination_dir), f)
+-          makedirs(dest[/.*(?=\/)/m])
+-          install src, dest, :mode => mode
+-        end
+-        File.chmod($dir_mode, destination_dir)
++  class DirPackage
++    attr_reader :spec
++
++    attr_accessor :dir_mode
++    attr_accessor :prog_mode
++    attr_accessor :data_mode
++
++    def initialize(spec)
++      @spec = spec
++      @src_dir = File.dirname(@spec.loaded_from)
++    end
++
++    def extract_files(destination_dir, pattern = "*")
++      path = @src_dir
++      return if path == destination_dir
++      File.chmod(0700, destination_dir)
++      mode = pattern == "bin/*" ? $script_mode : $data_mode
++      spec.files.each do |f|
++        src = File.join(path, f)
++        dest = File.join(without_destdir(destination_dir), f)
++        makedirs(dest[/.*(?=\/)/m])
++        install src, dest, :mode => mode
+       end
++      File.chmod($dir_mode, destination_dir)
+     end
++  end
+ 
+-    def initialize(spec, *options)
+-      super(spec.loaded_from, *options)
+-      @package.extend(DirPackage).spec = spec
+-    end
+-
++  class UnpackedInstaller < Gem::Installer
+     def write_cache_file
+     end
+ 
+@@ -890,7 +896,8 @@ def install_default_gem(dir, srcdir)
+     if File.directory?(ext = "#{gem_ext_dir}/#{spec.full_name}")
+       spec.extensions[0] ||= "-"
+     end
+-    ins = RbInstall::UnpackedInstaller.new(spec, options)
++    package = RbInstall::DirPackage.new spec
++    ins = RbInstall::UnpackedInstaller.new(package, options)
+     puts "#{INDENT}#{spec.name} #{spec.version}"
+     ins.install
+     File.chmod($data_mode, File.join(install_dir, "specifications", "#{spec.full_name}.gemspec"))
+-- 
+2.35.1
+