Editor: Allow file retrieval after code run

app/controllers/concerns/file_conversion.rb

@@ -0,0 +1,35 @@
+# frozen_string_literal: true
+
+module FileConversion
+  private
+
+  def convert_files_json_to_files(files_json)
+    all_file_types = FileType.all
+    directories = []
+    files = files_json['files'].filter_map do |file|
+      # entryType: `-` describes a regular file, `d` a directory. See `info ls` for others
+      directories.push(file['name']) if file['entryType'] == 'd'
+      next unless file['entryType'] == '-'
+
+      extension = File.extname(file['name'])
+      name = File.basename(file['name'], extension)
+      path = File.dirname(file['name']).sub(%r{^(?>\./|\.)}, '').presence
+      file_type = all_file_types.detect {|ft| ft.file_extension == extension } || FileType.new(file_extension: extension)
+      CodeOcean::File.new(
+        name: name,
+        path: path,
+        size: file['size'],
+        owner: file['owner'],
+        group: file['group'],
+        permissions: file['permissions'],
+        updated_at: file['modificationTime'],
+        file_type: file_type
+      )
+    end
+    [augment_files_for_download(files), directories]
+  end
+
+  def augment_files_for_download(files)
+    raise NotImplementedError
+  end
+end

app/controllers/live_streams_controller.rb

@@ -0,0 +1,70 @@
+# frozen_string_literal: true
+
+class LiveStreamsController < ApplicationController
+  # Including ActionController::Live changes all actions in this controller!
+  # Therefore, it is extracted into a separate controller
+  include ActionController::Live
+
+  def download_submission_file
+    begin
+      @submission = authorize AuthenticatedUrlHelper.retrieve!(Submission, request, force_render_host: false)
+    rescue Pundit::NotAuthorizedError
+      # TODO: Option to disable?
+      # Using the submission ID parameter would allow looking up the corresponding exercise ID
+      # Therefore, we just redirect to the root_path, but actually expect to redirect back (that should work!)
+      redirect_back(fallback_location: root_path, alert: t('exercises.download_file_tree.gone'))
+    end
+
+    desired_file = params[:filename].to_s
+    runner = Runner.for(current_user, @submission.exercise.execution_environment)
+    fallback_location = implement_exercise_path(@submission.exercise)
+    send_runner_file(runner, desired_file, fallback_location)
+  end
+
+  private
+
+  def send_runner_file(runner, desired_file, redirect_fallback = root_path)
+    filename = File.basename(desired_file)
+    send_stream(filename: filename, disposition: 'attachment') do |stream|
+      runner.download_file desired_file do |chunk, overall_size, content_type|
+        unless response.committed?
+          # Disable Rack::ETag, which would otherwise cause the response to be cached
+          # See https://github.com/rack/rack/issues/1619#issuecomment-848460528
+          response.set_header('Last-Modified', Time.now.httpdate)
+          response.set_header('Content-Length', overall_size) if overall_size
+          response.set_header('Content-Type', content_type) if content_type
+          # Commit the response headers immediately, as streaming would otherwise remove the Content-Length header
+          # This will prevent chunked transfer encoding from being used, which is okay as we know the overall size
+          # See https://github.com/rails/rails/issues/18714
+          response.commit!
+        end
+
+        if stream.connected?
+          stream.write chunk
+        else
+          # The client disconnected, so we stop streaming
+          break
+        end
+      end
+    rescue Runner::Error
+      redirect_back(fallback_location: redirect_fallback, alert: t('exercises.download_file_tree.gone'))
+    end
+  end
+
+  # TODO: Taken from Rails 7, remove when upgrading
+  # rubocop:disable all
+  def send_stream(filename:, disposition: "attachment", type: nil)
+    response.headers["Content-Type"] =
+      (type.is_a?(Symbol) ? Mime[type].to_s : type) ||
+        Mime::Type.lookup_by_extension(File.extname(filename).downcase.delete(".")) ||
+        "application/octet-stream"
+
+    response.headers["Content-Disposition"] =
+      ActionDispatch::Http::ContentDisposition.format(disposition: disposition, filename: filename)
+
+    yield response.stream
+  ensure
+    response.stream.close
+  end
+  # rubocop:enable all
+end

app/controllers/submissions_controller.rb

@@ -3,6 +3,7 @@
 class SubmissionsController < ApplicationController
   include CommonBehavior
   include Lti
+  include FileConversion
   include SubmissionParameters
   include Tubesock::Hijack
 
@@ -177,7 +178,7 @@ class SubmissionsController < ApplicationController
         send_and_store client_socket, message
       end
 
-      runner_socket.on :exit do |exit_code|
+      runner_socket.on :exit do |exit_code, files|
         @testrun[:exit_code] = exit_code
         exit_statement =
           if @testrun[:output].empty? && exit_code.zero?
@@ -200,6 +201,12 @@ class SubmissionsController < ApplicationController
           @testrun[:status] = :out_of_memory
         end
 
+        downloadable_files, = convert_files_json_to_files files
+        if downloadable_files.present?
+          js_tree = FileTree.new(downloadable_files).to_js_tree
+          send_and_store client_socket, {cmd: :files, data: js_tree}
+        end
+
         close_client_connection(client_socket)
       end
     end
@@ -427,4 +434,19 @@ class SubmissionsController < ApplicationController
   rescue JSON::ParserError
     {cmd: :write, stream: stream, data: data}
   end
+
+  def augment_files_for_download(files)
+    submission_files = @submission.collect_files
+    files.filter_map do |file|
+      # Reject files that were already present in the submission
+      # We further reject files that share the same name (excl. file extension) and path as a file in the submission
+      # This is, for example, used to filter compiled .class files in Java submissions
+      next if submission_files.any? {|submission_file| submission_file.filepath_without_extension == file.filepath_without_extension }
+
+      # Downloadable files get a signed download_path and an indicator whether we performed a privileged execution
+      file.download_path = AuthenticatedUrlHelper.sign(download_stream_file_submission_url(@submission, file.filepath), @submission)
+      file.privileged_execution = @submission.execution_environment.privileged_execution
+      file
+    end
+  end
 end