[Content Addressable] Add support for Packaging Single-ABI Gems

.github/actions/cibuildgem/action.yml

@@ -9,6 +9,10 @@ inputs:
   step:
     description: "The step to run"
     required: true
+  include-single-abi:
+    description: "Whether to also compile a set of single-ABI gems."
+    required: false
+    default: false
   test-command:
     description: "The command to run the test suite. By default cibuildgem will run either `bundle exec rake test` or `bundle exec rake spec` depending on the test framework used."
     required: false
@@ -41,7 +45,7 @@ runs:
       if: "${{ inputs.step == 'compile' }}"
       working-directory: ${{ inputs.working-directory }}
       shell: bash
-      run: cibuildgem package
+      run: cibuildgem package --include-single-abi "${{ inputs.include-single-abi }}"
     - name: Upload artifacts
       if: "${{ inputs.step == 'compile' }}"
       uses: actions/upload-artifact@v4

lib/cibuildgem/cli.rb

@@ -32,7 +32,7 @@ def compile
       run_rake_tasks!("cibuildgem:setup", :compile)
     end
 
-    desc "package", "Compile and package a 'fat gem'.", hide: true
+    desc "package", "Compile and package a 'multi-ABI gem'.", hide: true
     long_desc <<~MSG
       This command should normally run on CI, using the cibuildgem workflow. It will not work locally unless
       the environment is properly setup.
@@ -42,13 +42,20 @@ def compile
       - A gem without precompiled binary (Ruby platform).
 
       The gem with precompiled binaries will be packaged with multiple binaries compatible for different
-      Ruby ABI (depending on what Ruby version the gem supports).
+      Ruby ABI (depending on what Ruby version the gem supports). If `--include-single-abi` is passed,
+      cibuildgem will also compile a set of single-ABI gems per Ruby version supported by the gem.
     MSG
     method_option "gemspec", type: "string", required: false, desc: "The gemspec to use. Defaults to the gemspec from the current working directory."
+    method_option "include-single-abi", type: :boolean, required: false, default: false, desc: "Whether to also compile a set of single-ABI gems. Defaults to false."
     def package
       ENV["RUBY_CC_VERSION"] ||= compilation_task.ruby_cc_version
-
       run_rake_tasks!("cibuildgem:setup", :cross, :native, :gem)
+      if options["include-single-abi"] == true
+        compilation_task.ruby_versions.each do |ruby_version|
+          ENV["RUBY_CC_VERSION"] = ruby_version.to_s
+          run_rake_tasks!("cibuildgem:setup", :cross, :native, :gem)
+        end
+      end
     end
 
     desc "test", "Run the test suites of the target gem"

lib/cibuildgem/compilation_tasks.rb

@@ -25,11 +25,13 @@ def setup
       setup_packaging if create_packaging_task
     end
 
-    def ruby_cc_version
+    def ruby_versions
       required_ruby_version = @gemspec.required_ruby_version
-      selected_rubies = RubySeries.versions_to_compile_against(required_ruby_version)
+      RubySeries.versions_to_compile_against(required_ruby_version)
+    end
 
-      selected_rubies.map(&:to_s).join(":")
+    def ruby_cc_version
+      ruby_versions.map(&:to_s).join(":")
     end
 
     def normalized_platform
@@ -45,6 +47,9 @@ def normalized_platform
     private
 
     def setup_packaging
+      # Creates a Gem::PackageTask for the ordinary Ruby gem.
+      # Elsewhere in rake-compiler we also create one for the compiled gem.
+      # Internally in PackageTask, we define the :gem rake task which calls Gem::Package.build.
       Gem::PackageTask.new(gemspec) do |pkg|
         pkg.need_zip = true
         pkg.need_tar = true

test/cli_test.rb

@@ -303,6 +303,72 @@ def test_package_when_a_rakefile_defines_an_extension_task
       assert_predicate($CHILD_STATUS, :success?)
     end
 
+    def test_package_single_abi_runs_rake_tasks_for_each_ruby_version
+      cli = CLI.new([], { "include-single-abi" => true })
+      compilation_task = Struct.new(:ruby_cc_version, :ruby_versions).new("3.3.8:3.2.8", [
+        Gem::Version.new("3.3.8"),
+        Gem::Version.new("3.2.8"),
+      ])
+      rake_calls = []
+      run_rake_tasks = proc do |*tasks|
+        rake_calls << [ENV.fetch("RUBY_CC_VERSION"), tasks]
+      end
+
+      cli.stub(:compilation_task, compilation_task) do
+        cli.stub(:run_rake_tasks!, run_rake_tasks) do
+          cli.package
+        end
+      end
+
+      expected_tasks = ["cibuildgem:setup", :cross, :native, :gem]
+      assert_equal(
+        [
+          ["3.3.8:3.2.8", expected_tasks],
+          ["3.3.8", expected_tasks],
+          ["3.2.8", expected_tasks],
+        ],
+        rake_calls,
+      )
+    end
+
+    def test_package_defaults_to_multi_abi
+      cli = CLI.new
+      compilation_task = Struct.new(:ruby_cc_version).new("3.3.8:3.2.8")
+      rake_calls = []
+      run_rake_tasks = proc do |*tasks|
+        rake_calls << [ENV.fetch("RUBY_CC_VERSION"), tasks]
+      end
+
+      cli.stub(:compilation_task, compilation_task) do
+        cli.stub(:run_rake_tasks!, run_rake_tasks) do
+          cli.package
+        end
+      end
+
+      assert_equal(
+        [["3.3.8:3.2.8", ["cibuildgem:setup", :cross, :native, :gem]]],
+        rake_calls,
+      )
+    end
+
+    def test_package_multi_abi_preserves_ruby_cc_version_from_environment
+      ENV["RUBY_CC_VERSION"] = "3.1.6"
+      cli = CLI.new
+      compilation_task = Struct.new(:ruby_cc_version).new("3.3.8:3.2.8")
+      ruby_cc_versions_used = []
+      run_rake_tasks = proc do |*|
+        ruby_cc_versions_used << ENV.fetch("RUBY_CC_VERSION")
+      end
+
+      cli.stub(:compilation_task, compilation_task) do
+        cli.stub(:run_rake_tasks!, run_rake_tasks) do
+          cli.package
+        end
+      end
+
+      assert_equal(["3.1.6"], ruby_cc_versions_used)
+    end
+
     def test_keep_the_extension_task_config_defined_by_the_gem
       Dir.chdir("test/fixtures/with_configured_ext") do
         cli = CLI.new