[Content Addressable] Support content addressable gem builds / gem naming in PackageTask

[OughtPuts]

#9900

NB Blocked behind: #9906 which changes the arguments for Gem::Package.build.

TLDR

Adds support to Gem::PackageTask for building single-ABI, content-addressable gems.

Description

This PR:

1. Adds an optional ruby_abi attribute to Gem::PackageTask.

2. Passes ruby_abi to Gem::Package.build, allowing it to produce a content-addressable gem for that
   Ruby ABI.

3. Uses a predictable .gem-built stamp file as the Rake build target when ruby_abi is present. This
   is necessary because the content-addressable gem filename contains a hash that is not known until the
   gem has been built.

4. Writes the path of the generated content-addressable gem into the stamp file. When ruby_abi is not
   provided, Gem::PackageTask retains its existing behaviour and uses the traditional gem path as its
   build target.

Testing

Tests in test_gem_package_task.rb verify that:

• ruby_abi is passed to Gem::Package.build;
• the content-addressable filename returned by Gem::Package.build is moved into the package directory;
• the stamp file is created and contains the path of the generated gem; and
• the existing packaging behaviour remains unchanged when no Ruby ABI is provided.

Top Hat

This has been top-hatted as part of the complete flow. See the cibuildgem CA support PR for more information.

[girachawda]

LGTM! I can't actually give you the ✅ but tophat passed and the code makes sense. Edouard's comments above make sense ^

[OughtPuts]

Putting this in draft temporarily until we are aligned on any changes needed to the --ruby_abi build flag.

[OughtPuts]

--content-addressable changes added here and upstream but still in draft awaiting the upstream parts to merge.

[jenshenny]

This PR is looking good to me 👍

[jenshenny]

Updated PR description:

TLDR

Adds Gem::PackageTask#content_addressable. When true, the gem task builds a content addressable gem for the single Ruby ABI identified by gem_spec.required_ruby_version.

Includes commits from #9906, please look at the last commit.

Description

Gem::PackageTask uses the gem's file path as its Rake target: file "pkg/foo-1.0.0-x86_64-linux.gem" => files. A content addressable gem's file name contains the hash of its contents, so it isn't known until the gem has been built and can't be a Rake target. This PR:

1. Adds content_addressable (default false) and passes it through to Gem::Package.build. The Ruby ABI comes from gem_spec.required_ruby_version via Gem::ContentAddress.ruby_abi_for, so the spec must already be in the ~> X.Y.0 form that content addressable gems require; nothing is inferred from a separate ruby_abi setting.

2. Uses a stamp file as the Rake target in content addressable mode: pkg/<full_name>-<ruby abi>.gem-built, containing the path of the built gem. On the next run the stamp is removed if the gem it points to no longer exists, so the gem is rebuilt; otherwise Rake's normal staleness check applies.

3. Suffixes the staging directory with the Ruby ABI (package_dir_path → pkg/<full_name>-<ruby abi>). A build that produces a multi ABI gem and several single ABI gems for the same full_name (rake-compiler#257) would otherwise share pkg/<full_name>/ between all of them. This lets every gem land directly in pkg/.

When content_addressable is false nothing changes: the target is the gem path, the staging directory is pkg/<full_name>, and Gem::Package.build is called with content_addressable = false.

Testing

A one-file gem packaged with Gem::PackageTask directly:

# Rakefile
require "rubygems/package_task"

spec = Gem::Specification.new do |s|
  s.name = "hello"
  s.version = "1.0.0"
  s.summary = "hello"
  s.authors = ["x"]
  s.files = ["lib/hello.rb"]
  s.platform = "arm64-darwin"
  s.required_ruby_version = "~> 4.0.0"
end

Gem::PackageTask.new(spec) do |pkg|
  pkg.content_addressable = true
end

$ rake gem
  Successfully built RubyGem
  File: hello-1.0.0-fa8b73c3.gem
  Platform: arm64-darwin
  Ruby ABI: 4.0

$ ls -p pkg
hello-1.0.0-arm64-darwin-4.0/           # staging dir, suffixed with the ABI
hello-1.0.0-arm64-darwin-4.0.gem-built  # stamp, the Rake target
hello-1.0.0-fa8b73c3.gem                # the gem

$ cat pkg/hello-1.0.0-arm64-darwin-4.0.gem-built
pkg/hello-1.0.0-fa8b73c3.gem

[kou]

+1