ruby: use stdenv derivation for patching RubyGems

Rather than rolling our own. This means that we can use all of the
extra functionality stdenv gives us, like being able to provide a list
of patches rather than just one.

pkgs/development/interpreters/ruby/default.nix

@@ -11,14 +11,7 @@ let
   opString = lib.optionalString;
   patchSet = import ./rvm-patchsets.nix { inherit fetchFromGitHub; };
   config = import ./config.nix { inherit fetchFromSavannah; };
-  rubygemsSrc = import ./rubygems-src.nix { inherit fetchurl; };
-  rubygemsPatch = fetchpatch {
-    url = "https://github.com/zimbatm/rubygems/compare/v2.6.6...v2.6.6-nix.patch";
-    sha256 = "0297rdb1m6v75q8665ry9id1s74p9305dv32l95ssf198liaihhd";
-  };
-  unpackdir = obj:
-    lib.removeSuffix ".tgz"
-      (lib.removeSuffix ".tar.gz" obj.name);
+  rubygems = import ./rubygems.nix { inherit stdenv lib fetchurl fetchpatch; };
 
   # Contains the ruby version heuristics
   rubyVersion = import ./ruby-version.nix { inherit lib; };
@@ -49,8 +42,10 @@ let
       , buildEnv, bundler, bundix
       , libiconv, libobjc, libunwind, Foundation
       }:
-      let rubySrc =
-        if useRailsExpress then fetchFromGitHub {
+      stdenv.mkDerivation rec {
+        name = "ruby-${version}";
+
+        src = if useRailsExpress then fetchFromGitHub {
           owner  = "ruby";
           repo   = "ruby";
           rev    = tag;
@@ -59,16 +54,6 @@ let
           url = "https://cache.ruby-lang.org/pub/ruby/${ver.majMin}/ruby-${ver}.tar.gz";
           sha256 = sha256.src;
         };
-      in
-      stdenv.mkDerivation rec {
-        name = "ruby-${version}";
-
-        srcs = [ rubySrc rubygemsSrc ];
-        sourceRoot =
-          if useRailsExpress then
-            rubySrc.name
-          else
-            unpackdir rubySrc;
 
         # Have `configure' avoid `/usr/bin/nroff' in non-chroot builds.
         NROFF = if docSupport then "${groff}/bin/nroff" else null;
@@ -100,10 +85,7 @@ let
           })."${ver.majMinTiny}";
 
         postUnpack = ''
-          cp -r ${unpackdir rubygemsSrc} ${sourceRoot}/rubygems
-          pushd ${sourceRoot}/rubygems
-          patch -p1 < ${rubygemsPatch}
-          popd
+          cp -r ${rubygems} $sourceRoot/rubygems
         '';
 
         postPatch = if atLeast25 then ''
@@ -146,6 +128,7 @@ let
         postInstall = ''
           # Update rubygems
           pushd rubygems
+          chmod +w bundler/bundler.gemspec
           ${buildRuby} setup.rb --destdir $GEM_HOME
           popd
 

pkgs/development/interpreters/ruby/rubygems-src.nix

@@ -1,8 +0,0 @@
-{ fetchurl
-, version ? "2.7.7"
-, sha256 ? "1jsmmd31j8j066b83lin4bbqz19jhrirarzb41f3sjhfdjiwkcjc"
-}:
-fetchurl {
-  url = "https://rubygems.org/rubygems/rubygems-${version}.tgz";
-  sha256 = sha256;
-}

pkgs/development/interpreters/ruby/rubygems.nix

@@ -0,0 +1,31 @@
+{ stdenv, lib, fetchurl, fetchpatch }:
+
+stdenv.mkDerivation rec {
+  name = "rubygems";
+  version = "2.7.7";
+
+  src = fetchurl {
+    url = "https://rubygems.org/rubygems/rubygems-${version}.tgz";
+    sha256 = "1jsmmd31j8j066b83lin4bbqz19jhrirarzb41f3sjhfdjiwkcjc";
+  };
+
+  patches = [
+    (fetchpatch {
+      url = "https://github.com/zimbatm/rubygems/compare/v2.6.6...v2.6.6-nix.patch";
+      sha256 = "0297rdb1m6v75q8665ry9id1s74p9305dv32l95ssf198liaihhd";
+    })
+  ];
+
+  installPhase = ''
+    runHook preInstall
+    cp -r . $out
+    runHook postInstall
+  '';
+
+  meta = with lib; {
+    description = "Package management framework for Ruby";
+    homepage = https://rubygems.org/;
+    license = with licenses; [ mit /* or */ ruby ];
+    maintainers = with maintainers; [ qyliss zimbatm ];
+  };
+}