Remove stale plugin wrappers even when --no-install-plugin is specified

When a gem upgrades from a version with plugins to one without,
generate_plugins normally removes the old wrapper files. Skipping
generate_plugins entirely with --no-install-plugin prevented this
cleanup, leaving stale wrappers that would still be loaded.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

Author: hsbt

bundler/lib/bundler/rubygems_gem_installer.rb

@@ -40,6 +40,7 @@ def install
       end
 
       if options[:install_plugin] == false
+        remove_stale_plugins
         warn_skipped_plugins
       else
         generate_plugins

lib/rubygems/installer.rb

@@ -292,6 +292,7 @@ def install
 
     generate_bin
     if options[:install_plugin] == false
+      remove_stale_plugins
       warn_skipped_plugins
     else
       generate_plugins
@@ -831,6 +832,13 @@ def warn_skipped_plugins # :nodoc:
                   "To install plugins, run: gem pristine #{spec.name} --only-plugins"
   end
 
+  def remove_stale_plugins # :nodoc:
+    return unless spec.plugins.empty?
+
+    ensure_writable_dir @plugins_dir
+    remove_plugins_for(spec, @plugins_dir)
+  end
+
   ##
   # Reads the file index and extracts each file into the gem directory.
   #

test/rubygems/test_gem_installer.rb

@@ -2539,6 +2539,39 @@ def test_install_no_install_plugin_without_plugins
     refute_match "contains plugins", @ui.error
   end
 
+  def test_install_no_install_plugin_removes_stale_wrappers
+    # First install a version with a plugin
+    installer = util_setup_installer do |spec|
+      write_file File.join(@tempdir, "lib", "rubygems_plugin.rb") do |io|
+        io.write "# plugin code"
+      end
+
+      spec.files += %w[lib/rubygems_plugin.rb]
+    end
+
+    build_rake_in do
+      use_ui @ui do
+        installer.install
+      end
+    end
+
+    plugin_path = File.join Gem.plugindir, "a_plugin.rb"
+    assert File.exist?(plugin_path), "plugin wrapper should exist after first install"
+
+    # Now install a new version without plugins, using --no-install-plugin
+    spec2 = quick_gem "a", 3
+    util_build_gem spec2
+
+    installer2 = util_installer spec2, @gemhome
+    installer2.options[:install_plugin] = false
+
+    use_ui @ui do
+      installer2.install
+    end
+
+    refute File.exist?(plugin_path), "stale plugin wrapper must be removed"
+  end
+
   private
 
   def util_execless