Prefer `flat_map` over `map` + `flatten` in specs

Although `flat_map` is equivalent to `map` + `flatten(1)`
(note the level 1) we can apply this same refactoring to all cases.

spec/controllers/projects/jobs_controller_spec.rb

@@ -158,7 +158,7 @@ describe Projects::JobsController, :clean_gitlab_redis_shared_state do
         get_show_json
 
         json_response.dig('pipeline', 'details', 'stages').tap do |stages|
-          expect(stages.map(&:keys).flatten)
+          expect(stages.flat_map(&:keys))
             .to eq %w[name title status path dropdown_path]
         end
       end

spec/lib/gitlab/database_importers/common_metrics/importer_spec.rb

@@ -7,8 +7,8 @@ describe Gitlab::DatabaseImporters::CommonMetrics::Importer do
 
   context "does import common_metrics.yml" do
     let(:groups) { subject.content['panel_groups'] }
-    let(:panels) { groups.map { |group| group['panels'] }.flatten }
-    let(:metrics) { panels.map { |group| group['metrics'] }.flatten }
+    let(:panels) { groups.flat_map { |group| group['panels'] } }
+    let(:metrics) { panels.flat_map { |group| group['metrics'] } }
     let(:metric_ids) { metrics.map { |metric| metric['id'] } }
 
     before do

spec/lib/gitlab/import_export/project_tree_saver_spec.rb

@@ -179,9 +179,9 @@ describe Gitlab::ImportExport::ProjectTreeSaver do
       end
 
       it 'has priorities associated to labels' do
-        priorities = saved_project_json['issues'].first['label_links'].map { |link| link['label']['priorities'] }
+        priorities = saved_project_json['issues'].first['label_links'].flat_map { |link| link['label']['priorities'] }
 
-        expect(priorities.flatten).not_to be_empty
+        expect(priorities).not_to be_empty
       end
 
       it 'has issue resource label events' do

spec/lib/gitlab/metrics/dashboard/processor_spec.rb

@@ -101,9 +101,9 @@ describe Gitlab::Metrics::Dashboard::Processor do
   private
 
   def all_metrics
-    dashboard[:panel_groups].map do |group|
-      group[:panels].map { |panel| panel[:metrics] }
-    end.flatten
+    dashboard[:panel_groups].flat_map do |group|
+      group[:panels].flat_map { |panel| panel[:metrics] }
+    end
   end
 
   def get_metric_details(metric)

spec/lib/gitlab/prometheus/metric_group_spec.rb

@@ -17,7 +17,7 @@ describe Gitlab::Prometheus::MetricGroup do
     end
 
     it 'returns exactly three metric queries' do
-      expect(subject.map(&:metrics).flatten.map(&:id)).to contain_exactly(
+      expect(subject.flat_map(&:metrics).map(&:id)).to contain_exactly(
         common_metric_group_a.id, common_metric_group_b_q1.id,
         common_metric_group_b_q2.id)
     end
@@ -37,7 +37,7 @@ describe Gitlab::Prometheus::MetricGroup do
 
     subject do
       described_class.for_project(other_project)
-        .map(&:metrics).flatten
+        .flat_map(&:metrics)
         .map(&:id)
     end
 

spec/models/wiki_page_spec.rb

@@ -81,10 +81,9 @@ describe WikiPage do
           grouped_entries = described_class.group_by_directory(wiki.list_pages)
 
           actual_order =
-            grouped_entries.map do |page_or_dir|
+            grouped_entries.flat_map do |page_or_dir|
               get_slugs(page_or_dir)
             end
-            .flatten
           expect(actual_order).to eq(expected_order)
         end
       end

spec/services/issuable/bulk_update_service_spec.rb

@@ -265,7 +265,7 @@ describe Issuable::BulkUpdateService do
         end
 
         it 'removes the label IDs from all issues passed' do
-          expect(issues.map(&:reload).map(&:label_ids).flatten).not_to include(merge_requests.id)
+          expect(issues.map(&:reload).flat_map(&:label_ids)).not_to include(merge_requests.id)
         end
 
         it 'does not update issues not passed in' do
@@ -297,11 +297,11 @@ describe Issuable::BulkUpdateService do
         let(:remove_labels) { [regression] }
 
         it 'removes the label IDs from all issues passed' do
-          expect(issues.map(&:reload).map(&:label_ids).flatten).not_to include(regression.id)
+          expect(issues.map(&:reload).flat_map(&:label_ids)).not_to include(regression.id)
         end
 
         it 'ignores the label IDs parameter' do
-          expect(issues.map(&:reload).map(&:label_ids).flatten).not_to include(merge_requests.id)
+          expect(issues.map(&:reload).flat_map(&:label_ids)).not_to include(merge_requests.id)
         end
 
         it 'does not update issues not passed in' do
@@ -320,11 +320,11 @@ describe Issuable::BulkUpdateService do
         end
 
         it 'removes the label IDs from all issues passed' do
-          expect(issues.map(&:reload).map(&:label_ids).flatten).not_to include(merge_requests.id)
+          expect(issues.map(&:reload).flat_map(&:label_ids)).not_to include(merge_requests.id)
         end
 
         it 'ignores the label IDs parameter' do
-          expect(issues.map(&:reload).map(&:label_ids).flatten).not_to include(regression.id)
+          expect(issues.map(&:reload).flat_map(&:label_ids)).not_to include(regression.id)
         end
 
         it 'does not update issues not passed in' do

spec/services/issues/update_service_spec.rb

@@ -179,7 +179,7 @@ describe Issues::UpdateService, :mailer do
         it 'sends email to user2 about assign of new issue and email to user3 about issue unassignment' do
           deliveries = ActionMailer::Base.deliveries
           email = deliveries.last
-          recipients = deliveries.last(2).map(&:to).flatten
+          recipients = deliveries.last(2).flat_map(&:to)
           expect(recipients).to include(user2.email, user3.email)
           expect(email.subject).to include(issue.title)
         end

spec/services/merge_requests/update_service_spec.rb

@@ -99,7 +99,7 @@ describe MergeRequests::UpdateService, :mailer do
       it 'sends email to user2 about assign of new merge request and email to user3 about merge request unassignment' do
         deliveries = ActionMailer::Base.deliveries
         email = deliveries.last
-        recipients = deliveries.last(2).map(&:to).flatten
+        recipients = deliveries.last(2).flat_map(&:to)
         expect(recipients).to include(user2.email, user3.email)
         expect(email.subject).to include(merge_request.title)
       end

spec/support/helpers/key_generator_helper.rb

@@ -33,7 +33,7 @@ module Spec
 
         # Packs string components into an openssh-encoded pubkey.
         def pack_pubkey_components(strings)
-          (strings.map { |s| [s.length].pack('N') }).zip(strings).flatten.join
+          (strings.flat_map { |s| [s.length].pack('N') }).zip(strings).join
         end
       end
     end