1 files changed, 52 insertions, 0 deletions
diff --git a/lib/bundler/installer/standalone.rb b/lib/bundler/installer/standalone.rb
new file mode 100644
index 0000000000..03411d85e2
--- /dev/null
+++ b/lib/bundler/installer/standalone.rb
@@ -0,0 +1,52 @@
+# frozen_string_literal: true
+module Bundler
+  class Standalone
+    def initialize(groups, definition)
+      @specs = groups.empty? ? definition.requested_specs : definition.specs_for(groups.map(&:to_sym))
+    end
+
+    def generate
+      SharedHelpers.filesystem_access(bundler_path) do |p|
+        FileUtils.mkdir_p(p)
+      end
+      File.open File.join(bundler_path, "setup.rb"), "w" do |file|
+        file.puts "require 'rbconfig'"
+        file.puts "# ruby 1.8.7 doesn't define RUBY_ENGINE"
+        file.puts "ruby_engine = defined?(RUBY_ENGINE) ? RUBY_ENGINE : 'ruby'"
+        file.puts "ruby_version = RbConfig::CONFIG[\"ruby_version\"]"
+        file.puts "path = File.expand_path('..', __FILE__)"
+        paths.each do |path|
+          file.puts %($:.unshift "\#{path}/#{path}")
+        end
+      end
+    end
+
+  private
+
+    def paths
+      @specs.map do |spec|
+        next if spec.name == "bundler"
+        Array(spec.require_paths).map do |path|
+          gem_path(path, spec).sub(version_dir, '#{ruby_engine}/#{ruby_version}')
+          # This is a static string intentionally. It's interpolated at a later time.
+        end
+      end.flatten
+    end
+
+    def version_dir
+      "#{Bundler::RubyVersion.system.engine}/#{RbConfig::CONFIG["ruby_version"]}"
+    end
+
+    def bundler_path
+      Bundler.root.join(Bundler.settings[:path], "bundler")
+    end
+
+    def gem_path(path, spec)
+      full_path = Pathname.new(path).absolute? ? path : File.join(spec.full_gem_path, path)
+      Pathname.new(full_path).relative_path_from(Bundler.root.join(bundler_path)).to_s
+    rescue TypeError
+      error_message = "#{spec.name} #{spec.version} has an invalid gemspec"
+      raise Gem::InvalidSpecificationException.new(error_message)
+    end
+  end
+end