Fetch custom Ruby version file specified by ruby file: option in Gemfile

Add support for Bundler's `ruby file: "filename"` syntax, which allows
managing the Ruby version via an external file. The FileFetcher now
fetches the referenced file as a support file.

- Add `ruby_file_version_filename` to extract the filename from Gemfile
  content using a regex
- Add `ruby_file_version_file` to fetch the file via `fetch_support_file`
- Wire it into `fetch_files` following the same pattern as `.ruby-version` and `.tool-versions`

ref: ruby/rubygems@fb9354b

Author: wt-l00

bundler/lib/dependabot/bundler/file_fetcher.rb

@@ -50,6 +50,7 @@ def fetch_files
         fetched_files += gemspecs
         fetched_files << T.must(ruby_version_file) if ruby_version_file
         fetched_files << T.must(tool_versions_file) if tool_versions_file
+        fetched_files << T.must(ruby_file_version_file) if ruby_file_version_file
         fetched_files += path_gemspecs
         fetched_files += find_included_files(fetched_files)
 
@@ -138,6 +139,28 @@ def tool_versions_file
         @tool_versions_file ||= T.let(fetch_support_file(".tool-versions"), T.nilable(Dependabot::DependencyFile))
       end
 
+      sig { returns(T.nilable(DependencyFile)) }
+      def ruby_file_version_file
+        return unless gemfile
+
+        @ruby_file_version_file ||= T.let(
+          begin
+            filename = ruby_file_version_filename
+            fetch_support_file(filename) if filename
+          end,
+          T.nilable(Dependabot::DependencyFile)
+        )
+      end
+
+      sig { returns(T.nilable(String)) }
+      def ruby_file_version_filename
+        content = gemfile&.content
+        return unless content
+
+        match = content.match(/^\s*ruby\s+file:\s*['"]([^'"]+)['"]/)
+        match&.captures&.first
+      end
+
       sig { returns(T::Array[DependencyFile]) }
       def path_gemspecs
         gemspec_files = T.let([], T::Array[Dependabot::DependencyFile])

bundler/lib/dependabot/bundler/file_parser/file_preparer.rb

@@ -35,6 +35,7 @@ def prepared_dependency_files
             lockfile,
             ruby_version_file,
             tool_versions_file,
+            ruby_file_version_file,
             *imported_ruby_files,
             *specification_files
           ].compact
@@ -89,6 +90,24 @@ def tool_versions_file
           dependency_files.find { |f| f.name == ".tool-versions" }
         end
 
+        # `ruby file: "..."` で指定されたカスタム Ruby バージョンファイルを返す
+        sig { returns(T.nilable(Dependabot::DependencyFile)) }
+        def ruby_file_version_file
+          filename = ruby_file_version_filename
+          return unless filename
+
+          dependency_files.find { |f| f.name == filename }
+        end
+
+        sig { returns(T.nilable(String)) }
+        def ruby_file_version_filename
+          content = gemfile&.content
+          return unless content
+
+          match = content.match(/^\s*ruby\s+file:\s*['"]([^'"]+)['"]/)
+          match&.captures&.first
+        end
+
         sig { returns(T::Array[Dependabot::DependencyFile]) }
         def imported_ruby_files
           dependency_files

bundler/lib/dependabot/bundler/file_updater/lockfile_updater.rb

@@ -132,6 +132,7 @@ def write_temporary_dependency_files
           write_gemspecs(top_level_gemspecs)
           write_ruby_version_file
           write_tool_versions_file
+          write_ruby_file_version_file
           write_gemspecs(path_gemspecs)
           write_specification_files
           write_imported_ruby_files
@@ -161,6 +162,16 @@ def write_tool_versions_file
           File.write(path, T.must(tool_versions_file).content)
         end
 
+        # `ruby file: "..."` で指定されたカスタム Ruby バージョンファイルを一時ディレクトリに書き出す
+        sig { void }
+        def write_ruby_file_version_file
+          return unless ruby_file_version_file
+
+          path = T.must(ruby_file_version_file).name
+          FileUtils.mkdir_p(Pathname.new(path).dirname)
+          File.write(path, T.must(ruby_file_version_file).content)
+        end
+
         sig { params(files: T::Array[Dependabot::DependencyFile]).void }
         def write_gemspecs(files)
           files.each do |file|
@@ -218,6 +229,24 @@ def tool_versions_file
           dependency_files.find { |f| f.name == ".tool-versions" }
         end
 
+        # `ruby file: "..."` で指定されたカスタム Ruby バージョンファイルを返す
+        sig { returns(T.nilable(Dependabot::DependencyFile)) }
+        def ruby_file_version_file
+          filename = ruby_file_version_filename
+          return unless filename
+
+          dependency_files.find { |f| f.name == filename }
+        end
+
+        sig { returns(T.nilable(String)) }
+        def ruby_file_version_filename
+          content = gemfile&.content
+          return unless content
+
+          match = content.match(/^\s*ruby\s+file:\s*['"]([^'"]+)['"]/)
+          match&.captures&.first
+        end
+
         sig { params(lockfile_body: String).returns(String) }
         def post_process_lockfile(lockfile_body)
           lockfile_body = reorder_git_dependencies(lockfile_body)

bundler/lib/dependabot/bundler/update_checker/file_preparer.rb

@@ -114,11 +114,12 @@ def prepared_dependency_files
             )
           end
 
-          # No editing required for lockfile or Ruby version file
+          # lockfile や Ruby バージョンファイルは編集不要のためそのまま追加
           files += [
             lockfile,
             ruby_version_file,
             tool_versions_file,
+            ruby_file_version_file,
             *imported_ruby_files,
             *specification_files
           ].compact
@@ -200,6 +201,24 @@ def tool_versions_file
           dependency_files.find { |f| f.name == ".tool-versions" }
         end
 
+        # `ruby file: "..."` で指定されたカスタム Ruby バージョンファイルを返す
+        sig { returns(T.nilable(Dependabot::DependencyFile)) }
+        def ruby_file_version_file
+          filename = ruby_file_version_filename
+          return unless filename
+
+          dependency_files.find { |f| f.name == filename }
+        end
+
+        sig { returns(T.nilable(String)) }
+        def ruby_file_version_filename
+          content = gemfile&.content
+          return unless content
+
+          match = content.match(/^\s*ruby\s+file:\s*['"]([^'"]+)['"]/)
+          match&.captures&.first
+        end
+
         sig { returns(T::Array[Dependabot::DependencyFile]) }
         def path_gemspecs
           all = dependency_files.select { |f| f.name.end_with?(".gemspec") }

bundler/spec/dependabot/bundler/file_fetcher_spec.rb

@@ -205,6 +205,48 @@
     end
   end
 
+  context "with a custom version file referenced via `ruby file:` option" do
+    before do
+      stub_request(:get, url + "?ref=sha")
+        .with(headers: { "Authorization" => "token token" })
+        .to_return(
+          status: 200,
+          body: fixture("github", "contents_ruby_with_custom_version_file.json"),
+          headers: { "content-type" => "application/json" }
+        )
+
+      stub_request(:get, url + "Gemfile?ref=sha")
+        .with(headers: { "Authorization" => "token token" })
+        .to_return(
+          status: 200,
+          body: fixture("github", "gemfile_with_ruby_file_option_content.json"),
+          headers: { "content-type" => "application/json" }
+        )
+
+      stub_request(:get, url + "Gemfile.lock?ref=sha")
+        .with(headers: { "Authorization" => "token token" })
+        .to_return(
+          status: 200,
+          body: fixture("github", "gemfile_lock_content.json"),
+          headers: { "content-type" => "application/json" }
+        )
+
+      stub_request(:get, url + "custom-ruby-version?ref=sha")
+        .with(headers: { "Authorization" => "token token" })
+        .to_return(
+          status: 200,
+          body: fixture("github", "custom_ruby_version_content.json"),
+          headers: { "content-type" => "application/json" }
+        )
+    end
+
+    it "fetches the custom version file specified by `ruby file:` option" do
+      expect(file_fetcher_instance.files.count).to eq(3)
+      expect(file_fetcher_instance.files.map(&:name))
+        .to include("custom-ruby-version")
+    end
+  end
+
   context "with a gems.rb rather than a Gemfile" do
     before do
       stub_request(:get, url + "?ref=sha")

bundler/spec/dependabot/bundler/file_parser/file_preparer_spec.rb

@@ -58,6 +58,16 @@
       its(:content) { is_expected.to eq("ruby 2.2.0\n") }
     end
 
+    describe "the updated custom ruby version file specified by `ruby file:` option" do
+      subject do
+        prepared_dependency_files.find { |f| f.name == "custom-ruby-version" }
+      end
+
+      let(:dependency_files) { bundler_project_dependency_files("ruby_file_option") }
+
+      its(:content) { is_expected.to eq("2.2.0\n") }
+    end
+
     describe "the updated .specification file" do
       subject do
         prepared_dependency_files.find { |f| f.name == "plugins/example/.specification" }

bundler/spec/dependabot/bundler/file_updater_spec.rb

@@ -547,6 +547,24 @@
         end
       end
 
+      context "when the Gemfile loads a custom ruby version file via `ruby file:` option" do
+        let(:project_name) { "ruby_file_option" }
+        let(:updater) do
+          described_class.new(
+            dependency_files: dependency_files,
+            dependencies: [dependency],
+            credentials: [{
+              "type" => "git_source",
+              "host" => "github.com"
+            }]
+          )
+        end
+
+        it "locks the updated gem to the latest version" do
+          expect(file.content).to include "business (1.5.0)"
+        end
+      end
+
       context "when the Gemfile.lock didn't have a BUNDLED WITH line" do
         let(:project_name) { "no_bundled_with" }
 

bundler/spec/dependabot/bundler/update_checker/latest_version_finder_spec.rb

@@ -227,6 +227,12 @@
         its([:version]) { is_expected.to eq(Dependabot::Bundler::Version.new("1.5.0")) }
       end
 
+      context "when the Gemfile loads a custom ruby version file via `ruby file:` option" do
+        let(:dependency_files) { bundler_project_dependency_files("ruby_file_option") }
+
+        its([:version]) { is_expected.to eq(Dependabot::Bundler::Version.new("1.5.0")) }
+      end
+
       context "with a gemspec and a Gemfile" do
         let(:dependency_files) { bundler_project_dependency_files("gemfile_small_example") }
 

bundler/spec/fixtures/github/contents_ruby_with_custom_version_file.json

@@ -0,0 +1,50 @@
+[
+  {
+    "name": "Gemfile",
+    "path": "Gemfile",
+    "sha": "88b4e0a1c8093fae2b4fa52534035f9f85ed0956",
+    "size": 100,
+    "url": "https://api.github.com/repos/gocardless/bump/contents/Gemfile?ref=master",
+    "html_url": "https://github.com/gocardless/bump/blob/master/Gemfile",
+    "git_url": "https://api.github.com/repos/gocardless/bump/git/blobs/88b4e0a1c8093fae2b4fa52534035f9f85ed0956",
+    "download_url": "https://raw.githubusercontent.com/gocardless/bump/master/Gemfile",
+    "type": "file",
+    "_links": {
+      "self": "https://api.github.com/repos/gocardless/bump/contents/Gemfile?ref=master",
+      "git": "https://api.github.com/repos/gocardless/bump/git/blobs/88b4e0a1c8093fae2b4fa52534035f9f85ed0956",
+      "html": "https://github.com/gocardless/bump/blob/master/Gemfile"
+    }
+  },
+  {
+    "name": "Gemfile.lock",
+    "path": "Gemfile.lock",
+    "sha": "d429264c8c2f0f306a422900c2f41123e07c31b4",
+    "size": 100,
+    "url": "https://api.github.com/repos/gocardless/bump/contents/Gemfile.lock?ref=master",
+    "html_url": "https://github.com/gocardless/bump/blob/master/Gemfile.lock",
+    "git_url": "https://api.github.com/repos/gocardless/bump/git/blobs/d429264c8c2f0f306a422900c2f41123e07c31b4",
+    "download_url": "https://raw.githubusercontent.com/gocardless/bump/master/Gemfile.lock",
+    "type": "file",
+    "_links": {
+      "self": "https://api.github.com/repos/gocardless/bump/contents/Gemfile.lock?ref=master",
+      "git": "https://api.github.com/repos/gocardless/bump/git/blobs/d429264c8c2f0f306a422900c2f41123e07c31b4",
+      "html": "https://github.com/gocardless/bump/blob/master/Gemfile.lock"
+    }
+  },
+  {
+    "name": "custom-ruby-version",
+    "path": "custom-ruby-version",
+    "sha": "005119baaa0653ca59d923010341d8341daa8c43",
+    "size": 6,
+    "url": "https://api.github.com/repos/gocardless/bump/contents/custom-ruby-version?ref=master",
+    "html_url": "https://github.com/gocardless/bump/blob/master/custom-ruby-version",
+    "git_url": "https://api.github.com/repos/gocardless/bump/git/blobs/005119baaa0653ca59d923010341d8341daa8c43",
+    "download_url": "https://raw.githubusercontent.com/gocardless/bump/master/custom-ruby-version",
+    "type": "file",
+    "_links": {
+      "self": "https://api.github.com/repos/gocardless/bump/contents/custom-ruby-version?ref=master",
+      "git": "https://api.github.com/repos/gocardless/bump/git/blobs/005119baaa0653ca59d923010341d8341daa8c43",
+      "html": "https://github.com/gocardless/bump/blob/master/custom-ruby-version"
+    }
+  }
+]

bundler/spec/fixtures/github/custom_ruby_version_content.json

@@ -0,0 +1,18 @@
+{
+    "name": "custom-ruby-version",
+    "path": "custom-ruby-version",
+    "sha": "005119baaa0653ca59d923010341d8341daa8c43",
+    "size": 6,
+    "url": "https://api.github.com/repos/gocardless/bump/contents/custom-ruby-version?ref=master",
+    "html_url": "https://github.com/gocardless/bump/blob/master/custom-ruby-version",
+    "git_url": "https://api.github.com/repos/gocardless/bump/git/blobs/005119baaa0653ca59d923010341d8341daa8c43",
+    "download_url": "https://raw.githubusercontent.com/gocardless/bump/master/custom-ruby-version",
+    "type": "file",
+    "content": "My4yLjAK\n",
+    "encoding": "base64",
+    "_links": {
+        "self": "https://api.github.com/repos/gocardless/bump/contents/custom-ruby-version?ref=master",
+        "git": "https://api.github.com/repos/gocardless/bump/git/blobs/005119baaa0653ca59d923010341d8341daa8c43",
+        "html": "https://github.com/gocardless/bump/blob/master/custom-ruby-version"
+    }
+}