Retain current bundler version on bundle clean

bundler/lib/bundler/rubygems_integration.rb

@@ -432,7 +432,7 @@ def default_specs
     end
 
     def find_bundler(version)
-      find_name("bundler").find {|s| s.version.to_s == version }
+      find_name("bundler").find {|s| s.version.to_s == version.to_s }
     end
 
     def find_name(name)

bundler/lib/bundler/runtime.rb

@@ -174,7 +174,14 @@ def clean(dry_run = false)
       spec_cache_paths     = []
       spec_gemspec_paths   = []
       spec_extension_paths = []
-      Bundler.rubygems.add_default_gems_to(specs).values.each do |spec|
+      specs_to_keep = Bundler.rubygems.add_default_gems_to(specs).values
+
+      current_bundler = Bundler.rubygems.find_bundler(Bundler.gem_version)
+      if current_bundler
+        specs_to_keep << current_bundler
+      end
+
+      specs_to_keep.each do |spec|
         spec_gem_paths << spec.full_gem_path
         # need to check here in case gems are nested like for the rails git repo
         md = %r{(.+bundler/gems/.+-[a-f0-9]{7,12})}.match(spec.full_gem_path)

bundler/spec/commands/clean_spec.rb

@@ -898,4 +898,41 @@ def should_not_have_gems(*gems)
 
     expect(very_simple_binary_extensions_dir).to be_nil
   end
+
+  it "does not remove the bundler version currently running" do
+    gemfile <<-G
+      source "https://gem.repo1"
+
+      gem "myrack"
+    G
+
+    bundle "config set path vendor/bundle"
+    bundle "install"
+
+    version = Bundler.gem_version.to_s
+    # Simulate that the locked bundler version is installed in the bundle path
+    # by creating the gem directory and gemspec (as would happen after bundle install with that version)
+    Pathname(vendored_gems("cache/bundler-#{version}.gem")).tap do |path|
+      path.basename.mkpath
+      FileUtils.touch(path)
+    end
+    FileUtils.touch(vendored_gems("gems/bundler-#{version}"))
+    Pathname(vendored_gems("specifications/bundler-#{version}.gemspec")).tap do |path|
+      path.basename.mkpath
+      path.write(<<~GEMSPEC)
+        Gem::Specification.new do |s|
+          s.name = "bundler"
+          s.version = "#{version}"
+          s.authors = ["bundler team"]
+          s.summary = "The best way to manage your application's dependencies"
+        end
+      GEMSPEC
+    end
+
+    should_have_gems "bundler-#{version}"
+
+    bundle :clean
+
+    should_have_gems "bundler-#{version}"
+  end
 end