Implement Go modules proxy

ee/lib/api/go_proxy.rb

+# frozen_string_literal: true
+module API
+  class GoProxy < Grape::API
+    helpers ::API::Helpers::PackagesHelpers
+
+    SEMVER_REGEX = /v(0|[1-9]\d*)\.(0|[1-9]\d*)\.(0|[1-9]\d*)(-[-.A-Z0-9]+)?(\+[-.A-Z0-9]+)?/i.freeze
+    SEMVER_TAG_REGEX = Regexp.new("^#{SEMVER_REGEX.source}$").freeze
+    MODULE_VERSION_REQUIREMENTS = { :module_version => SEMVER_REGEX }
+
+    helpers do
+      def project_package_base
+        @project_package_base ||= Gitlab::Routing.url_helpers.project_url(user_project).split('://', 2)[1]
+      end
+
+      def check_module_name
+        module_name = params[:module_name].gsub(/![[:alpha:]]/) { |s| s[1..].upcase }
+
+        bad_request!('Module Name') if module_name.blank?
+
+        if module_name == project_package_base
+          [module_name, '']
+        elsif module_name.start_with?(project_package_base + '/')
+          [module_name, module_name[(project_package_base.length+1)..]]
+        else
+          not_found!
+        end
+      end
+
+      def module_version?(project, path, module_name, tag)
+        return false unless SEMVER_TAG_REGEX.match?(tag.name)
+        return false unless tag.dereferenced_target
+
+        gomod = project.repository.blob_at(tag.dereferenced_target.sha, path + '/go.mod')
+        return false unless gomod
+
+        mod = gomod.data.split("\n", 2).first
+        mod == 'module ' + module_name
+      end
+
+      def module_versions(project, path, module_name)
+        project.repository.tags.filter { |tag| module_version?(project, path, module_name, tag) }
+      end
+    end
+
+    params do
+      requires :id, type: String, desc: 'The ID of a project'
+    end
+    resource :projects, requirements: API::NAMESPACE_OR_PROJECT_REQUIREMENTS do
+      namespace ':id/packages/go/*module_name/@v' do
+        before do
+        end
+
+        desc 'Get all tagged versions for a given Go module' do
+          detail 'See `go help goproxy`, GET $GOPROXY/<module>/@v/list'
+        end
+        get 'list' do
+          module_name, path = check_module_name
+
+          content_type 'text/plain'
+          module_versions(user_project, path, module_name).map { |t| t.name }.join("\n")
+        end
+
+        desc 'Get information about the given module version' do
+          detail 'See `go help goproxy`, GET $GOPROXY/<module>/@v/<version>.info'
+        end
+        get ':module_version.info', :requirements => MODULE_VERSION_REQUIREMENTS do
+          module_name, path = check_module_name
+
+          tag = user_project.repository.tags.filter { |tag| tag.name == params[:module_version] }.first
+          not_found! unless tag && module_version?(user_project, path, module_name, tag)
+
+          {
+            "Version" => tag.name,
+            "Time" => tag.dereferenced_target.committed_date
+          }
+        end
+
+        desc 'Get the module file of the given module version' do
+          detail 'See `go help goproxy`, GET $GOPROXY/<module>/@v/<version>.mod'
+        end
+        get ':module_version.mod', :requirements => MODULE_VERSION_REQUIREMENTS do
+          module_name, path = check_module_name
+
+          tag = user_project.repository.tags.filter { |tag| tag.name == params[:module_version] }.first
+          not_found! unless tag && module_version?(user_project, path, module_name, tag)
+
+          content_type 'text/plain'
+          user_project.repository.blob_at(tag.dereferenced_target.sha, path + '/go.mod').data
+        end
+
+        desc 'Get a zip of the source of the given module version' do
+          detail 'See `go help goproxy`, GET $GOPROXY/<module>/@v/<version>.zip'
+        end
+        get ':module_version.zip', :requirements => MODULE_VERSION_REQUIREMENTS do
+          module_name, path = check_module_name
+
+          tag = user_project.repository.tags.filter { |tag| tag.name == params[:module_version] }.first
+          not_found! unless tag && module_version?(user_project, path, module_name, tag)
+
+          sha = tag.dereferenced_target.sha
+          tree = user_project.repository.tree(sha, path, recursive: true).entries.filter { |e| e.type == :blob }
+          nested = tree.filter { |e| e.name == 'go.mod' && !(path == '' && e.path == 'go.mod' || e.path == path + '/go.mod') }.map { |e| e.path[0..-7] }
+          files = tree.filter { |e| !nested.any? { |n| e.path.start_with? n } }
+
+          s = Zip::OutputStream.write_buffer do |zip|
+            files.each do |file|
+              zip.put_next_entry(file.path)
+              zip.write user_project.repository.blob_at(sha, file.path).data
+            end
+          end
+
+          header['Content-Disposition'] = ActionDispatch::Http::ContentDisposition.format(disposition: 'attachment', filename: tag.name + '.zip')
+          header['Content-Transfer-Encoding'] = 'binary'
+          content_type 'text/plain'
+          # content_type 'application/zip'
+          status :ok
+          body s.string
+        end
+      end
+    end
+  end
+end
\ No newline at end of file

ee/lib/ee/api/api.rb

@@ -38,6 +38,7 @@ module EE
         mount ::API::ConanPackages
         mount ::API::MavenPackages
         mount ::API::NpmPackages
+        mount ::API::GoProxy
         mount ::API::MergeTrains
         mount ::API::ProjectPackages
         mount ::API::GroupPackages