CSV format supported in Issues#index

app/controllers/projects/issues_controller.rb

@@ -51,6 +51,7 @@ class Projects::IssuesController < Projects::ApplicationController
     respond_to do |format|
       format.html
       format.atom { render layout: false }
+      format.csv
       format.json do
         render json: {
           html: view_to_html_string("projects/issues/_issues"),

app/views/projects/issues/index.csv.ruby

+columns = {
+  'Issue ID' => 'iid',
+  'Title' => 'title',
+  'State' => 'state',
+  'Description' => 'description',
+  'Author Id' => 'author_id',
+  'Assignee Id' => 'assignee_id',
+  'Due Date' => 'due_date',
+  'Created At' => 'created_at',
+  'Updated At' => 'updated_at'
+}
+
+CSV.generate do |csv|
+  csv << columns.keys
+
+  @issues.pluck(*columns.values).each do |row|
+    csv << row
+  end
+end

spec/features/issues/csv_spec.rb

+require 'spec_helper'
+
+describe 'Issues csv', feature: true do
+  let(:user)    { create(:user) }
+  let(:project) { create(:project, :public) }
+  let!(:issue)  { create(:issue, project: project) }
+
+  before do
+    login_as(user)
+    visit namespace_project_issues_path(project.namespace, project, format: :csv)
+  end
+
+  it 'downloads as a file' do
+    expect(page.response_headers['Content-Type']).to include('csv')
+  end
+
+  it 'includes title' do
+    expect(csv[0]['Title']).to eq issue.title
+  end
+
+  it 'includes description' do
+    expect(csv[0]['Description']).to eq issue.description
+  end
+end

spec/support/csv_helpers.rb

+module CsvHelpers
+  def csv
+    CSV.parse(body, headers: true)
+  end
+end
+
+RSpec.configure do |config|
+  config.include CsvHelpers, type: :feature
+end