Remove merge_trains_enabled column from project_ci_cd_settings table

Part of https://gitlab.com/gitlab-org/gitlab/issues/12796

See merge request https://gitlab.com/gitlab-org/gitlab/merge_requests/19701

app/models/project_ci_cd_setting.rb

@@ -4,7 +4,6 @@ class ProjectCiCdSetting < ApplicationRecord
   include IgnorableColumns
   # https://gitlab.com/gitlab-org/gitlab/issues/36651
   ignore_column :merge_trains_enabled, remove_with: '12.7', remove_after: '2019-12-22'
-
   belongs_to :project, inverse_of: :ci_cd_settings
 
   # The version of the schema that first introduced this model/table.

db/post_migrate/20191128162854_drop_project_ci_cd_settings_merge_trains_enabled.rb

+# frozen_string_literal: true
+
+class DropProjectCiCdSettingsMergeTrainsEnabled < ActiveRecord::Migration[5.2]
+  include Gitlab::Database::MigrationHelpers
+
+  DOWNTIME = false
+
+  disable_ddl_transaction!
+
+  def up
+    remove_column :project_ci_cd_settings, :merge_trains_enabled
+  end
+
+  def down
+    add_column_with_default :project_ci_cd_settings, :merge_trains_enabled, :boolean, default: false, allow_null: true
+  end
+end

db/schema.rb

@@ -3098,7 +3098,6 @@ ActiveRecord::Schema.define(version: 2020_01_08_155731) do
     t.integer "project_id", null: false
     t.boolean "group_runners_enabled", default: true, null: false
     t.boolean "merge_pipelines_enabled"
-    t.boolean "merge_trains_enabled", default: false, null: false
     t.integer "default_git_depth"
     t.index ["project_id"], name: "index_project_ci_cd_settings_on_project_id", unique: true
   end

ee/app/models/ee/project.rb

@@ -158,7 +158,7 @@ module EE
       delegate :log_jira_dvcs_integration_usage, :jira_dvcs_server_last_sync_at, :jira_dvcs_cloud_last_sync_at, to: :feature_usage
 
       delegate :merge_pipelines_enabled, :merge_pipelines_enabled=, :merge_pipelines_enabled?, :merge_pipelines_were_disabled?, to: :ci_cd_settings
-      delegate :merge_trains_enabled, :merge_trains_enabled=, :merge_trains_enabled?, to: :ci_cd_settings
+      delegate :merge_trains_enabled?, to: :ci_cd_settings
       delegate :actual_limits, to: :namespace, allow_nil: true
 
       validates :repository_size_limit,

ee/app/models/ee/project_ci_cd_setting.rb

@@ -8,9 +8,6 @@ module EE
       project.feature_available?(:merge_pipelines) && super
     end
 
-    # As of GitLab 12.1, merge trains option is enabled by default for all projects.
-    # We should drop `merge_trains_enabled` column after this application has been deployed.
-    # See more https://gitlab.com/gitlab-org/gitlab/issues/11222.
     def merge_trains_enabled?
       merge_pipelines_enabled? && project.feature_available?(:merge_trains) &&
         ::Feature.enabled?(:merge_trains_enabled, project, default_enabled: true)

ee/changelogs/unreleased/12796-remove-merge_trains_enabled-column-from-project_ci_cd_settings-t.yml

+title: Remove `project_ci_cd_settings.merge_trains_enabled` column
+merge_request: 19701
+author:
+type: removed

ee/spec/services/auto_merge/add_to_merge_train_when_pipeline_succeeds_service_spec.rb

@@ -18,7 +18,7 @@ describe AutoMerge::AddToMergeTrainWhenPipelineSucceedsService do
   before do
     stub_licensed_features(merge_trains: true, merge_pipelines: true)
     project.add_maintainer(user)
-    project.update!(merge_trains_enabled: true, merge_pipelines_enabled: true)
+    project.update!(merge_pipelines_enabled: true)
     allow(AutoMergeProcessWorker).to receive(:perform_async) { }
     merge_request.update_head_pipeline
   end

ee/spec/services/auto_merge/merge_train_service_spec.rb

@@ -21,7 +21,7 @@ describe AutoMerge::MergeTrainService do
     allow(AutoMergeProcessWorker).to receive(:perform_async) { }
 
     stub_licensed_features(merge_trains: true, merge_pipelines: true)
-    project.update!(merge_trains_enabled: true, merge_pipelines_enabled: true)
+    project.update!(merge_pipelines_enabled: true)
   end
 
   describe '#execute' do

ee/spec/services/merge_trains/refresh_merge_request_service_spec.rb

@@ -11,7 +11,7 @@ describe MergeTrains::RefreshMergeRequestService do
   before do
     project.add_maintainer(maintainer)
     stub_licensed_features(merge_pipelines: true, merge_trains: true)
-    project.update!(merge_pipelines_enabled: true, merge_trains_enabled: true)
+    project.update!(merge_pipelines_enabled: true)
   end
 
   describe '#execute' do

spec/migrations/drop_project_ci_cd_settings_merge_trains_enabled_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+require Rails.root.join('db', 'post_migrate', '20191128162854_drop_project_ci_cd_settings_merge_trains_enabled.rb')
+
+describe DropProjectCiCdSettingsMergeTrainsEnabled, :migration do
+  let!(:project_ci_cd_setting) { table(:project_ci_cd_settings) }
+
+  it 'correctly migrates up and down' do
+    reversible_migration do |migration|
+      migration.before -> {
+        expect(project_ci_cd_setting.column_names).to include("merge_trains_enabled")
+      }
+
+      migration.after -> {
+        project_ci_cd_setting.reset_column_information
+        expect(project_ci_cd_setting.column_names).not_to include("merge_trains_enabled")
+      }
+    end
+  end
+end

spec/services/auto_merge/merge_when_pipeline_succeeds_service_spec.rb

@@ -34,7 +34,7 @@ describe AutoMerge::MergeWhenPipelineSucceedsService do
 
     it { is_expected.to be_truthy }
 
-    context 'when the head piipeline succeeded' do
+    context 'when the head pipeline succeeded' do
       let(:pipeline_status) { :success }
 
       it { is_expected.to be_falsy }