Prevent rake compiler from defining application defined task:

- Gem that define a Rake Compiler task (pretty much all) interfere with
  our own. The reason we can't rely on the user defined task is
  because it's not configured for compiling fat gems, it is usually
  only configured to compile natively for development purposes.

  I also would like the configuration of cibuildgem to not interfere
  with the gem defined task and not have to ask maintainers to change
  basic configuration just to make compiling fat gems possible,
  cibuildgem should take care of this automatically.

  For reference, I originally decided to choose running the
  whole compilation dance in a subprocess and require the gem
  Rakefile because I felt this would be the right entrypoint to
  configure CIbuildgem if needed.

Author: Edouard-chin

lib/cibuildgem/cli.rb

@@ -137,8 +137,13 @@ def run_rake_tasks!(*tasks)
       rake_path = rake_specs.full_require_paths
       prism_path = Gem.loaded_specs["prism"].full_require_paths
       load_paths = (rake_compiler_path + rake_path + prism_path).join(File::PATH_SEPARATOR)
+      patch = File.expand_path("../extension_patch.rb", __FILE__)
 
-      system({ "RUBYLIB" => load_paths }, "bundle exec #{RbConfig.ruby} #{rake_executable} #{all_tasks} -R#{rakelibdir}", exception: true)
+      system(
+        { "RUBYLIB" => load_paths },
+        "bundle exec #{RbConfig.ruby} #{rake_executable} #{all_tasks} -R#{rakelibdir} -r #{patch}",
+        exception: true,
+      )
     end
 
     def compilation_task

lib/cibuildgem/compilation_tasks.rb

@@ -17,6 +17,8 @@ def initialize(create_packaging_task = false, gemspec = nil)
     end
 
     def setup
+      Rake::ExtensionTask.enable!
+
       gemspec.extensions.each do |path|
         binary_name = parse_extconf(path)
         define_task(path, binary_name)

lib/cibuildgem/extension_patch.rb

@@ -0,0 +1,25 @@
+# frozen_string_literal: true
+
+require "rake/extensiontask"
+
+module Cibuildgem
+  module ExtensionPatch
+    class << self
+      def prepended(mod)
+        class << mod
+          attr_accessor :enabled
+
+          def enable!
+            @enabled = true
+          end
+        end
+      end
+    end
+
+    def define
+      super if self.class.enabled
+    end
+  end
+end
+
+Rake::ExtensionTask.prepend(Cibuildgem::ExtensionPatch)

test/cli_test.rb

@@ -1,6 +1,7 @@
 # frozen_string_literal: true
 
 require "test_helper"
+require "english"
 
 module Cibuildgem
   class CLITest < Minitest::Test
@@ -214,6 +215,14 @@ def test_cli_test_command_when_no_test_or_spec_rake_task_is_defined
       end
     end
 
+    def test_package_when_a_rakefile_defines_an_extension_task
+      Dir.chdir("test/fixtures/with_ext") do
+        CLI.start(["package"])
+      end
+
+      assert_predicate($CHILD_STATUS, :success?)
+    end
+
     private
 
     def raise_instead_of_exit(&block)

test/fixtures/with_ext/Rakefile

@@ -0,0 +1,10 @@
+# frozen_string_literal: true
+
+require "rake/extensiontask"
+
+gemspec = Gem::Specification.load("foo.gemspec")
+Rake::ExtensionTask.new("foo", gemspec)
+
+raise "No rake task should have been defined" if Rake::Task.task_defined?(:native)
+
+exit(0)

test/fixtures/with_ext/foo.gemspec

@@ -0,0 +1,14 @@
+# frozen_string_literal: true
+
+Gem::Specification.new do |spec|
+  spec.name = "edouard-dummy_gem"
+  spec.version = "0.0.1"
+  spec.authors = ["Edouard CHIN"]
+  spec.email = ["[email protected]"]
+  spec.summary = "A gem that do nothing"
+  spec.description = "Don't use it, really."
+  spec.license = "MIT"
+  spec.files = []
+  spec.require_paths = ["lib"]
+  spec.extensions = ["ext/hello_world/extconf.rb"]
+end