Set X-Gemfile-Source when fetching gems

Since gemstash will only support RubyGems >= 2.4 (rubygems/gemstash#32),
we only set this header in RubyGems 2.0+.

.rubocop_todo.yml

@@ -256,6 +256,7 @@ Style/RescueModifier:
     - 'lib/bundler/fetcher.rb'
     - 'lib/bundler/resolver.rb'
     - 'spec/realworld/dependency_api_spec.rb'
+    - 'spec/realworld/gemfile_source_header_spec.rb'
 
 # Offense count: 1
 # Configuration parameters: Methods.

lib/bundler/rubygems_integration.rb

@@ -586,7 +586,8 @@ def download_gem(spec, uri, path)
         uri = Bundler.settings.mirror_for(uri)
         proxy = configuration[:http_proxy]
         dns = Resolv::DNS.new
-        fetcher = Gem::RemoteFetcher.new(proxy, dns)
+        fetcher = Bundler::GemRemoteFetcher.new(proxy, dns)
+        fetcher.headers = { "X-Gemfile-Source" => spec.remote.original_uri.to_s } if spec.remote.original_uri
         fetcher.download(spec, uri, path)
       end
 

spec/realworld/gemfile_source_header_spec.rb

@@ -0,0 +1,63 @@
+require "spec_helper"
+require "thread"
+
+describe "fetching dependencies with a mirrored source", :rubygems => ">= 2.0" do
+  let(:mirror) { "https://server.example.org" }
+  let(:original) { "http://127.0.0.1:#{@port}" }
+
+  before do
+    setup_server
+    bundle "config --local mirror.#{mirror} #{original}"
+  end
+
+  after { @t.kill }
+
+  it "sets the 'X-Gemfile-Source' header and bundles successfully" do
+    gemfile <<-G
+      source "#{mirror}"
+      gem 'weakling'
+    G
+
+    bundle :install
+
+    expect(out).to include("Installing weakling")
+    expect(out).to include("Bundle complete")
+    should_be_installed "weakling 0.0.3"
+  end
+
+  private
+
+  def setup_server
+    # need to hack, so we can require rack
+    old_gem_home = ENV["GEM_HOME"]
+    ENV["GEM_HOME"] = Spec::Path.base_system_gems.to_s
+    require "rack"
+    ENV["GEM_HOME"] = old_gem_home
+
+    @port = 21_459
+    @port += 1 while TCPSocket.new("127.0.0.1", @port) rescue false
+    @server_uri = "http://127.0.0.1:#{@port}"
+
+    require File.expand_path("../../support/artifice/endpoint_mirror_source", __FILE__)
+
+    @t = Thread.new {
+      Rack::Server.start(:app       => EndpointMirrorSource,
+                         :Host      => "0.0.0.0",
+                         :Port      => @port,
+                         :server    => "webrick",
+                         :AccessLog => [])
+    }.run
+
+    wait_for_server(@port)
+  end
+
+  def wait_for_server(port, seconds = 15)
+    tries = 0
+    sleep 0.5
+    TCPSocket.new("127.0.0.1", port)
+  rescue => e
+    raise(e) if tries > (seconds * 2)
+    tries += 1
+    retry
+  end
+end

spec/support/artifice/endpoint_mirror_source.rb

@@ -0,0 +1,13 @@
+require File.expand_path("../endpoint", __FILE__)
+
+class EndpointMirrorSource < Endpoint
+  get "/gems/:id" do
+    if request.env["HTTP_X_GEMFILE_SOURCE"] == "https://server.example.org/"
+      File.read("#{gem_repo1}/gems/#{params[:id]}")
+    else
+      halt 500
+    end
+  end
+end
+
+Artifice.activate_with(EndpointMirrorSource)