Add Merge Request CSV export service

Adds a new service to export a CSV
from a given collection of merge requests.

app/models/merge_request.rb

@@ -270,6 +270,8 @@ class MergeRequest < ApplicationRecord
                metrics: [:latest_closed_by, :merged_by])
   }
 
+  scope :with_csv_entity_associations, -> { preload(:assignees, :approved_by_users, :author, :milestone, metrics: [:merged_by]) }
+
   scope :by_target_branch_wildcard, ->(wildcard_branch_name) do
     where("target_branch LIKE ?", ApplicationRecord.sanitize_sql_like(wildcard_branch_name).tr('*', '%'))
   end

app/services/merge_requests/export_csv_service.rb

+# frozen_string_literal: true
+
+module MergeRequests
+  class ExportCsvService
+    include Gitlab::Routing.url_helpers
+    include GitlabRoutingHelper
+
+    # Target attachment size before base64 encoding
+    TARGET_FILESIZE = 15.megabytes
+
+    def initialize(merge_requests)
+      @merge_requests = merge_requests
+    end
+
+    def csv_data
+      csv_builder.render(TARGET_FILESIZE)
+    end
+
+    private
+
+    def csv_builder
+      @csv_builder ||= CsvBuilder.new(@merge_requests.with_csv_entity_associations, header_to_value_hash)
+    end
+
+    def header_to_value_hash
+      {
+        'MR IID' => 'iid',
+        'URL' => -> (merge_request) { merge_request_url(merge_request) },
+        'Title' => 'title',
+        'State' => 'state',
+        'Description' => 'description',
+        'Source Branch' => 'source_branch',
+        'Target Branch' => 'target_branch',
+        'Source Project ID' => 'source_project_id',
+        'Target Project ID' => 'target_project_id',
+        'Author' => -> (merge_request) { merge_request.author.name },
+        'Author Username' => -> (merge_request) { merge_request.author.username },
+        'Assignees' => -> (merge_request) { merge_request.assignees.map(&:name).join(', ') },
+        'Assignee Usernames' => -> (merge_request) { merge_request.assignees.map(&:username).join(', ') },
+        'Approvers' => -> (merge_request) { merge_request.approved_by_users.map(&:name).join(', ') },
+        'Approver Usernames' => -> (merge_request) { merge_request.approved_by_users.map(&:username).join(', ') },
+        'Merged User' => -> (merge_request) { merge_request.metrics&.merged_by&.name.to_s },
+        'Merged Username' => -> (merge_request) { merge_request.metrics&.merged_by&.username.to_s },
+        'Milestone ID' => -> (merge_request) { merge_request&.milestone&.id || '' },
+        'Created At (UTC)' => -> (merge_request) { merge_request.created_at.utc },
+        'Updated At (UTC)' => -> (merge_request) { merge_request.updated_at.utc }
+      }
+    end
+  end
+end

spec/services/merge_requests/export_csv_service_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+RSpec.describe MergeRequests::ExportCsvService do
+  let_it_be(:merge_request) { create(:merge_request) }
+  let(:csv) { CSV.parse(subject.csv_data, headers: true).first }
+
+  subject { described_class.new(MergeRequest.where(id: merge_request.id)) }
+
+  describe 'csv_data' do
+    it 'contains the correct information', :aggregate_failures do
+      expect(csv['MR IID']).to eq(merge_request.iid.to_s)
+      expect(csv['Title']).to eq(merge_request.title)
+      expect(csv['State']).to eq(merge_request.state)
+      expect(csv['Description']).to eq(merge_request.description)
+      expect(csv['Source Branch']).to eq(merge_request.source_branch)
+      expect(csv['Target Branch']).to eq(merge_request.target_branch)
+      expect(csv['Source Project ID']).to eq(merge_request.source_project_id.to_s)
+      expect(csv['Target Project ID']).to eq(merge_request.target_project_id.to_s)
+      expect(csv['Author']).to eq(merge_request.author.name)
+      expect(csv['Author Username']).to eq(merge_request.author.username)
+    end
+
+    describe 'assignees' do
+      context 'when assigned' do
+        let_it_be(:merge_request) { create(:merge_request, assignees: create_list(:user, 2)) }
+
+        it 'contains the names of assignees' do
+          expect(csv['Assignees']).to eq(merge_request.assignees.map(&:name).join(', '))
+        end
+
+        it 'contains the usernames of assignees' do
+          expect(csv['Assignee Usernames']).to eq(merge_request.assignees.map(&:username).join(', '))
+        end
+      end
+
+      context 'when not assigned' do
+        it 'returns empty strings' do
+          expect(csv['Assignees']).to eq('')
+          expect(csv['Assignee Usernames']).to eq('')
+        end
+      end
+    end
+
+    describe 'approvers' do
+      context 'when approved' do
+        let_it_be(:merge_request) { create(:merge_request) }
+        let(:approvers) { create_list(:user, 2) }
+
+        before do
+          merge_request.approved_by_users = approvers
+        end
+
+        it 'contains the names of approvers separated by a comma' do
+          expect(csv['Approvers'].split(', ')).to contain_exactly(approvers[0].name, approvers[1].name)
+        end
+
+        it 'contains the usernames of approvers separated by a comma' do
+          expect(csv['Approver Usernames'].split(', ')).to contain_exactly(approvers[0].username, approvers[1].username)
+        end
+      end
+
+      context 'when not approved' do
+        it 'returns empty strings' do
+          expect(csv['Approvers']).to eq('')
+          expect(csv['Approver Usernames']).to eq('')
+        end
+      end
+    end
+
+    describe 'merged user' do
+      context 'MR is merged' do
+        let_it_be(:merge_request) { create(:merge_request, :merged, :with_merged_metrics) }
+
+        it 'is merged' do
+          expect(csv['State']).to eq('merged')
+        end
+
+        it 'has a merged user' do
+          expect(csv['Merged User']).to eq(merge_request.metrics.merged_by.name)
+          expect(csv['Merged Username']).to eq(merge_request.metrics.merged_by.username)
+        end
+      end
+
+      context 'MR is not merged' do
+        it 'returns empty strings' do
+          expect(csv['Merged User']).to eq('')
+          expect(csv['Merged Username']).to eq('')
+        end
+      end
+    end
+
+    describe 'milestone' do
+      context 'milestone is assigned' do
+        let_it_be(:merge_request) { create(:merge_request) }
+        let_it_be(:milestone) { create(:milestone, :active, project: merge_request.project) }
+
+        before do
+          merge_request.update!(milestone_id: milestone.id)
+        end
+
+        it 'contains the milestone ID' do
+          expect(csv['Milestone ID']).to eq(merge_request.milestone.id.to_s)
+        end
+      end
+
+      context 'no milestone is assigned' do
+        it 'returns an empty string' do
+          expect(csv['Milestone ID']).to eq('')
+        end
+      end
+    end
+  end
+end