Compensate for Rubygems' usage of .gemrc sources

lib/bundler/fetcher.rb

@@ -200,9 +200,6 @@ def fetch_dependency_remote_specs(gem_names)
 
     # fetch from modern index: specs.4.8.gz
     def fetch_all_remote_specs
-      # Ensure config is loaded so it doesn't get lazy-loaded later, overwriting Gem.sources!
-      Bundler.rubygems.configuration
-
       @has_api = false
       Bundler.rubygems.sources = ["#{@remote_uri}"]
 

lib/bundler/rubygems_integration.rb

@@ -35,6 +35,11 @@ def inflate(obj)
     end
 
     def sources=(val)
+      # Gem.configuration creates a new Gem::ConfigFile, which by default will read ~/.gemrc
+      # If that file exists, its settings (including sources) will overwrite the values we
+      # are about to set here. In order to avoid that, we force memoizing the config file now.
+      configuration
+
       Gem.sources = val
     end
 

spec/install/gems/dependency_api_spec.rb

@@ -433,4 +433,26 @@ def fetch(*)
     end
   end
 
+  context ".gemrc with sources is present" do
+    before do
+      File.open(home('.gemrc'), 'w') do |file|
+        file.puts({:sources => ["http://rubygems.org"]}.to_yaml)
+      end
+    end
+
+    after do
+      home('.gemrc').rmtree
+    end
+
+    it "uses other sources declared in the Gemfile" do
+      gemfile <<-G
+        source "#{source_uri}"
+        gem 'rack'
+      G
+
+      bundle "install", :exitstatus => true, :artifice => "endpoint_marshal_fail"
+
+      expect(exitstatus).to eq(0)
+    end
+  end
 end