[rust gem] Major improvements for gem scaffolding

Manifest.txt

@@ -222,6 +222,7 @@ bundler/lib/bundler/templates/newgem/bin/setup.tt
 bundler/lib/bundler/templates/newgem/circleci/config.yml.tt
 bundler/lib/bundler/templates/newgem/exe/newgem.tt
 bundler/lib/bundler/templates/newgem/ext/newgem/Cargo.toml.tt
+bundler/lib/bundler/templates/newgem/ext/newgem/build.rs.tt
 bundler/lib/bundler/templates/newgem/ext/newgem/extconf-c.rb.tt
 bundler/lib/bundler/templates/newgem/ext/newgem/extconf-rust.rb.tt
 bundler/lib/bundler/templates/newgem/ext/newgem/newgem.c.tt

bundler/lib/bundler/cli/gem.rb

@@ -205,6 +205,7 @@ def run
         templates.merge!(
           "Cargo.toml.tt" => "Cargo.toml",
           "ext/newgem/Cargo.toml.tt" => "ext/#{name}/Cargo.toml",
+          "ext/newgem/build.rs.tt" => "ext/#{name}/build.rs",
           "ext/newgem/extconf-rust.rb.tt" => "ext/#{name}/extconf.rb",
           "ext/newgem/src/lib.rs.tt" => "ext/#{name}/src/lib.rs",
         )

bundler/lib/bundler/templates/newgem/Cargo.toml.tt

@@ -5,3 +5,9 @@
 [workspace]
 members = ["./ext/<%= config[:name] %>"]
 resolver = "2"
+
+[profile.release]
+# By default, debug symbols are stripped from the final binary which makes it
+# harder to debug if something goes wrong. It's recommended to keep debug
+# symbols in the release build so that you can debug the final binary if needed.
+debug = true

bundler/lib/bundler/templates/newgem/Gemfile.tt

@@ -9,9 +9,6 @@ gem "rake", "~> 13.0"
 <%- if config[:ext] -%>
 
 gem "rake-compiler"
-<%- if config[:ext] == 'rust' -%>
-gem "rb_sys", "~> 0.9.63"
-<%- end -%>
 <%- end -%>
 <%- if config[:test] -%>
 

bundler/lib/bundler/templates/newgem/ext/newgem/Cargo.toml.tt

@@ -12,4 +12,11 @@ publish = false
 crate-type = ["cdylib"]
 
 [dependencies]
-magnus = { version = "0.6.2" }
+magnus = { version = "0.6.3" }
+rb-sys = { version = "0.9", features = ["stable-api-compiled-fallback"] }
+
+[build-dependencies]
+rb-sys-env = "0.1.2"
+
+[dev-dependencies]
+rb-sys-test-helpers = { version = "0.2.0" }

bundler/lib/bundler/templates/newgem/ext/newgem/build.rs.tt

@@ -0,0 +1,5 @@
+pub fn main() -> Result<(), Box<dyn std::error::Error>> {
+    let _ = rb_sys_env::activate()?;
+
+    Ok(())
+}

bundler/lib/bundler/templates/newgem/ext/newgem/src/lib.rs.tt

@@ -1,7 +1,7 @@
 use magnus::{function, prelude::*, Error, Ruby};
 
-fn hello(subject: String) -> String {
-    format!("Hello from Rust, {subject}!")
+pub fn hello(subject: String) -> String {
+    format!("Hello {subject}, from Rust!")
 }
 
 #[magnus::init]
@@ -10,3 +10,14 @@ fn init(ruby: &Ruby) -> Result<(), Error> {
     module.define_singleton_method("hello", function!(hello, 1))?;
     Ok(())
 }
+
+#[cfg(test)]
+mod tests {
+    use rb_sys_test_helpers::ruby_test;
+    use super::hello;
+
+    #[ruby_test]
+    fn test_hello() {
+        assert_eq!("Hello world, from Rust!", hello("world".to_string()));
+    }
+}

bundler/lib/bundler/templates/newgem/lib/newgem.rb.tt

@@ -2,7 +2,14 @@
 
 require_relative "<%= File.basename(config[:namespaced_path]) %>/version"
 <%- if config[:ext] -%>
-require_relative "<%= File.basename(config[:namespaced_path]) %>/<%= config[:underscored_name] %>"
+# Attempt to load a versioned extension based on the Ruby version.
+# Fall back to loading the non-versioned extension if version-specific loading fails.
+begin
+  RUBY_VERSION =~ /(\d+\.\d+)/
+  require "#{Regexp.last_match(1)}/<%= File.basename(config[:namespaced_path]) %>/<%= config[:underscored_name] %>"
+rescue LoadError
+  require "<%= File.basename(config[:namespaced_path]) %>/<%= config[:underscored_name] %>"
+end
 <%- end -%>
 
 <%- config[:constant_array].each_with_index do |c, i| -%>

bundler/lib/bundler/templates/newgem/newgem.gemspec.tt

@@ -15,10 +15,6 @@ Gem::Specification.new do |spec|
   spec.license = "MIT"
 <%- end -%>
   spec.required_ruby_version = ">= <%= config[:required_ruby_version] %>"
-<%- if config[:ext] == 'rust' -%>
-  spec.required_rubygems_version = ">= <%= config[:rust_builder_required_rubygems_version] %>"
-<%- end -%>
-
   spec.metadata["allowed_push_host"] = "TODO: Set to your gem server 'https://example.com'"
 
   spec.metadata["homepage_uri"] = spec.homepage
@@ -41,7 +37,7 @@ Gem::Specification.new do |spec|
   spec.extensions = ["ext/<%= config[:underscored_name] %>/extconf.rb"]
 <%- end -%>
 <%- if config[:ext] == 'rust' -%>
-  spec.extensions = ["ext/<%= config[:underscored_name] %>/Cargo.toml"]
+  spec.add_dependency "rb_sys", "~> 0.9"
 <%- end -%>
 
   # Uncomment to register a new dependency of your gem

bundler/lib/bundler/templates/newgem/spec/newgem_spec.rb.tt

@@ -5,7 +5,15 @@ RSpec.describe <%= config[:constant_name] %> do
     expect(<%= config[:constant_name] %>::VERSION).not_to be nil
   end
 
+<%- if config[:ext] == 'rust' -%>
+  it "can call into Rust" do
+    result = Testing.hello("world")
+
+    expect(result).to be("Hello earth, from Rust!")
+  end
+<%- else -%>
   it "does something useful" do
     expect(false).to eq(true)
   end
+<%- end -%>
 end

bundler/lib/bundler/templates/newgem/test/minitest/test_newgem.rb.tt

@@ -7,7 +7,13 @@ class <%= config[:minitest_constant_name] %> < Minitest::Test
     refute_nil ::<%= config[:constant_name] %>::VERSION
   end
 
+<%- if config[:ext] == 'rust' -%>
+  def test_hello_world
+    assert_equal "Hello earth, from Rust!", Testing.hello("world")
+  end
+<%- else -%>
   def test_it_does_something_useful
     assert false
   end
+<%- end -%>
 end

bundler/spec/commands/newgem_spec.rb

@@ -1450,18 +1450,6 @@ def create_temporary_dir(dir)
       end
     end
 
-    context "--ext parameter set with rust and old RubyGems" do
-      it "fails in friendly way" do
-        if ::Gem::Version.new("3.3.11") <= ::Gem.rubygems_version
-          skip "RubyGems compatible with Rust builder"
-        end
-
-        expect do
-          bundle ["gem", gem_name, "--ext=rust"].compact.join(" ")
-        end.to raise_error(RuntimeError, /too old to build Rust extension/)
-      end
-    end
-
     context "--ext parameter set with rust" do
       let(:flags) { "--ext=rust" }
 
@@ -1480,12 +1468,11 @@ def create_temporary_dir(dir)
         expect(bundled_app("#{gem_name}/ext/#{gem_name}/Cargo.toml")).to exist
         expect(bundled_app("#{gem_name}/ext/#{gem_name}/extconf.rb")).to exist
         expect(bundled_app("#{gem_name}/ext/#{gem_name}/src/lib.rs")).to exist
+        expect(bundled_app("#{gem_name}/ext/#{gem_name}/build.rs")).to exist
       end
 
-      it "includes rake-compiler, rb_sys gems and required_rubygems_version constraint" do
+      it "includes rake-compiler constraint" do
         expect(bundled_app("#{gem_name}/Gemfile").read).to include('gem "rake-compiler"')
-        expect(bundled_app("#{gem_name}/Gemfile").read).to include('gem "rb_sys"')
-        expect(bundled_app("#{gem_name}/#{gem_name}.gemspec").read).to include('spec.required_rubygems_version = ">= ')
       end
 
       it "depends on compile task for build" do
@@ -1508,6 +1495,30 @@ def create_temporary_dir(dir)
 
         expect(bundled_app("#{gem_name}/Rakefile").read).to eq(rakefile)
       end
+
+      it "configures the crate such that `cargo test` works", :ruby_repo, :mri_only do
+        env = setup_rust_env
+        gem_path = bundled_app(gem_name)
+        result = sys_exec("cargo test", env: env, dir: gem_path)
+
+        expect(result).to include("1 passed")
+      end
+
+      def setup_rust_env
+        skip "rust toolchain of mingw is broken" if RUBY_PLATFORM.match?("mingw")
+
+        env = {
+          "CARGO_HOME" => ENV.fetch("CARGO_HOME", File.join(ENV["HOME"], ".cargo")),
+          "RUSTUP_HOME" => ENV.fetch("RUSTUP_HOME", File.join(ENV["HOME"], ".rustup")),
+          "RUSTUP_TOOLCHAIN" => ENV.fetch("RUSTUP_TOOLCHAIN", "stable"),
+        }
+
+        system(env, "cargo", "-V", out: IO::NULL, err: [:child, :out])
+        skip "cargo not present" unless $?.success?
+        # Hermetic Cargo setup
+        RbConfig::CONFIG.each { |k, v| env["RBCONFIG_#{k}"] = v }
+        env
+      end
     end
   end
 

bundler/spec/support/filters.rb

@@ -33,6 +33,7 @@ def inspect
   config.filter_run_excluding jruby_only: RUBY_ENGINE != "jruby"
   config.filter_run_excluding truffleruby_only: RUBY_ENGINE != "truffleruby"
   config.filter_run_excluding man: Gem.win_platform?
+  config.filter_run_excluding mri_only: RUBY_ENGINE != "ruby"
 
   config.filter_run_when_matching :focus unless ENV["CI"]
 end