[PostIt] Update to add legacy RubyGems support

2 files changed, 15 insertions, 4 deletions

diff --git a/lib/bundler/vendor/postit/lib/postit/installer.rb b/lib/bundler/vendor/postit/lib/postit/installer.rb
index 30a74a0190..6fc98560e7 100644
--- a/lib/bundler/vendor/postit/lib/postit/installer.rb
+++ b/lib/bundler/vendor/postit/lib/postit/installer.rb
@@ -5,13 +5,24 @@ module BundlerVendoredPostIt
     end
 
     def installed?
-      !Gem::Specification.find_by_name('bundler', @bundler_version).nil?
+      if Gem::Specification.respond_to?(:find_by_name)
+        !Gem::Specification.find_by_name('bundler', @bundler_version).nil?
+      else
+        dep = Gem::Dependency.new('bundler', @bundler_version)
+        Gem.source_index.gems.values.any? do |s|
+          dep.match?(s.name, s.version)
+        end
+      end
     rescue LoadError
       false
     end
 
     def install!
-      Gem.install('bundler', @bundler_version) unless installed?
+      return if installed?
+      require "rubygems/dependency_installer"
+      installer = Gem::DependencyInstaller.new
+      installer.install('bundler', @bundler_version)
+      installer.installed_gems
     end
   end
 end
diff --git a/spec/other/trampoline_spec.rb b/spec/other/trampoline_spec.rb
index f172f62ac8..640c608508 100644
--- a/spec/other/trampoline_spec.rb
+++ b/spec/other/trampoline_spec.rb
@@ -82,10 +82,10 @@ describe "bundler version trampolining" do
     it "fails gracefully when installing the bundler fails" do
       ENV["BUNDLER_VERSION"] = "9999"
       bundle "--version", :expect_err => true
-      expect(err).to eq(<<-E.strip)
+      expect(err).to start_with(<<-E.strip)
 Installing the inferred bundler version (= 9999) failed.
 If you'd like to update to the current bundler version (1.12.5) in this project, run `bundle update --bundler`.
-The error was: Unable to resolve dependency: user requested 'bundler (= 9999)'
+The error was:
       E
     end
   end