DEV: Custom generator for move setting from tl to groups (#24912)

Ability to automatically generate migration when site setting is changed from trust level to groups.

Example usage:

rails generate site_setting_move_to_groups_migration min_trust_to_create_topic create_topic_allowed_groups

spec/generator/site_setting_move_to_groups_migrations_generator_spec.rb

@@ -0,0 +1,125 @@
+# frozen_string_literal: true
+
+require "rails_helper"
+require "rails/generators"
+require "generators/site_setting_move_to_groups_migration/site_setting_move_to_groups_migration_generator"
+
+RSpec.describe SiteSettingMoveToGroupsMigrationGenerator, type: :generator do
+  it "generates the correct migration for TrustLevelSetting" do
+    freeze_time DateTime.parse("2010-01-01 12:00")
+    described_class
+      .any_instance
+      .expects(:load_settings)
+      .returns({ branding: { "site_description" => { enum: "TrustLevelSetting" } } })
+
+    described_class.start(%w[site_description contact_email], destination_root: "#{Rails.root}/tmp")
+    file_path =
+      "#{Rails.root}/tmp/db/migrate/20100101120000_fill_contact_email_based_on_deprecated_setting.rb"
+
+    expected_content = <<~EXPECTED_CONTENT
+      # frozen_string_literal: true
+
+      class FillContactEmailBasedOnDeprecatedSetting < ActiveRecord::Migration[7.0]
+        def up
+          old_setting_trust_level =
+            DB.query_single(
+              "SELECT value FROM site_settings WHERE name = 'site_description' LIMIT 1",
+            ).first
+
+          if old_setting_trust_level.present?
+            allowed_groups = "1\#\{old_setting_trust_level\}"
+
+            DB.exec(
+              "INSERT INTO site_settings(name, value, data_type, created_at, updated_at)
+              VALUES('contact_email', :setting, '20', NOW(), NOW())",
+              setting: allowed_groups,
+            )
+          end
+        end
+
+        def down
+          raise ActiveRecord::IrreversibleMigration
+        end
+      end
+    EXPECTED_CONTENT
+
+    expect(File.read(file_path)).to eq(expected_content)
+    File.delete(file_path)
+  end
+
+  it "generates the correct migration for TrustLevelAndStaffSetting" do
+    freeze_time DateTime.parse("2010-01-01 12:00")
+    described_class
+      .any_instance
+      .expects(:load_settings)
+      .returns({ branding: { "title" => { enum: "TrustLevelAndStaffSetting" } } })
+
+    described_class.start(%w[title contact_email], destination_root: "#{Rails.root}/tmp")
+    file_path =
+      "#{Rails.root}/tmp/db/migrate/20100101120000_fill_contact_email_based_on_deprecated_setting.rb"
+
+    expected_content = <<~EXPECTED_CONTENT
+      # frozen_string_literal: true
+
+      class FillContactEmailBasedOnDeprecatedSetting < ActiveRecord::Migration[7.0]
+        def up
+          old_setting_trust_level =
+            DB.query_single(
+              "SELECT value FROM site_settings WHERE name = 'title' LIMIT 1",
+            ).first
+
+          if old_setting_trust_level.present?
+            allowed_groups =
+              case old_setting_trust_level
+              when "admin"
+                "1"
+              when "staff"
+                "3"
+              when "0"
+                "10"
+              when "1"
+                "11"
+              when "2"
+                "12"
+              when "3"
+                "13"
+              when "4"
+                "14"
+              end
+
+            DB.exec(
+              "INSERT INTO site_settings(name, value, data_type, created_at, updated_at)
+              VALUES('contact_email', :setting, '20', NOW(), NOW())",
+              setting: allowed_groups,
+            )
+          end
+        end
+
+        def down
+          raise ActiveRecord::IrreversibleMigration
+        end
+      end
+    EXPECTED_CONTENT
+
+    expect(File.read(file_path)).to eq(expected_content)
+    File.delete(file_path)
+  end
+
+  it "raises an error when old name is incorrect" do
+    expect { described_class.start(%w[wrong_name contact_email]) }.to raise_error(ArgumentError)
+  end
+
+  it "raises an error when new name is incorrect" do
+    expect { described_class.start(%w[site_description wrong_name]) }.to raise_error(ArgumentError)
+  end
+
+  it "raises an error when old setting is incorrect type" do
+    described_class
+      .any_instance
+      .expects(:load_settings)
+      .returns({ branding: { "site_description" => { enum: "EmojiSetSiteSetting" } } })
+    expect { described_class.start(%w[site_description contact_email]) }.to raise_error(
+      ArgumentError,
+    )
+  end
+end