[ruby/rubygems] Add debug logging information:

- I'd like to be able to see how long bundler takes for basic
  operations such as downloading a gem from Rubygems.org and
  installing a gem.

  It will now be possible with this commit by running
  `DEBUG=true bundle install` and have output that looks like:

  Fetching rack-test 2.2.0
  Downloaded rack-test in: 50.523s
  Installing rack-test 2.2.0
  Installed rack-test in: : 0.003s

ruby/rubygems@46386d43e1

Author: Edouard-chin

lib/bundler/source/rubygems.rb

@@ -211,7 +211,11 @@ def install(spec, options = {})
         message += " with native extensions" if spec.extensions.any?
         Bundler.ui.confirm message
 
-        installed_spec = installer.install
+        installed_spec = nil
+
+        Gem.time("Installed #{spec.name} in", 0, true) do
+          installed_spec = installer.install
+        end
 
         spec.full_gem_path = installed_spec.full_gem_path
         spec.loaded_from = installed_spec.loaded_from
@@ -478,7 +482,10 @@ def download_gem(spec, download_cache_path, previous_spec = nil)
         uri = spec.remote.uri
         Bundler.ui.confirm("Fetching #{version_message(spec, previous_spec)}")
         gem_remote_fetcher = remote_fetchers.fetch(spec.remote).gem_remote_fetcher
-        Bundler.rubygems.download_gem(spec, uri, download_cache_path, gem_remote_fetcher)
+
+        Gem.time("Downloaded #{spec.name} in", 0, true) do
+          Bundler.rubygems.download_gem(spec, uri, download_cache_path, gem_remote_fetcher)
+        end
       end
 
       # Returns the global cache path of the calling Rubygems::Source object.

spec/bundler/bundler/source/rubygems_spec.rb

@@ -44,4 +44,22 @@
       end
     end
   end
+
+  describe "log debug information" do
+    it "log the time spent downloading and installing a gem" do
+      build_repo2 do
+        build_gem "warning"
+      end
+
+      gemfile_content = <<~G
+        source "https://gem.repo2"
+        gem "warning"
+      G
+
+      stdout = install_gemfile(gemfile_content, env: { "DEBUG" => "1" })
+
+      expect(stdout).to match(/Downloaded warning in: \d+\.\d+s/)
+      expect(stdout).to match(/Installed warning in: \d+\.\d+s/)
+    end
+  end
 end