Make sure native extensions are loaded correctly in ext_conf builder

1 files changed, 15 insertions, 1 deletions

diff --git a/lib/rubygems/ext/ext_conf_builder.rb b/lib/rubygems/ext/ext_conf_builder.rb
index cabafaed05..f8fed2a8bf 100644
--- a/lib/rubygems/ext/ext_conf_builder.rb
+++ b/lib/rubygems/ext/ext_conf_builder.rb
@@ -21,9 +21,23 @@ class Gem::Ext::ExtConfBuilder < Gem::Ext::Builder
 
     destdir = ENV["DESTDIR"]
 
+    # This is only needed when running rubygems test without a proper installation.
+    # Prepending it in a normal installation can cause problem with order of $LOAD_PATH.
+    # Therefore only add rubygems_load_path if it is not present in the default $LOAD_PATH.
+    rubygems_load_path = File.expand_path("../..", __dir__)
+    load_path =
+      case rubygems_load_path
+      when RbConfig::CONFIG["sitelibdir"], RbConfig::CONFIG["vendorlibdir"], RbConfig::CONFIG["rubylibdir"]
+        []
+      else
+        ["-I#{rubygems_load_path}"]
+      end
+
     begin
       require "shellwords"
-      cmd = Gem.ruby.shellsplit << "-I" << File.expand_path("../..", __dir__) << File.basename(extension)
+      cmd = Gem.ruby.shellsplit
+      cmd.push(*load_path)
+      cmd << File.basename(extension)
       cmd.push(*args)
 
       run(cmd, results, class_name, extension_dir) do |s, r|