adjust migration to proxy call to ActiveRecord

By adding proxy method the call to ActiveRecord::Migrator.migrations_paths
is decoupled from the migration task allowing more flexibility for the
underlying migration set selection to change in future Rails versions.

lib/msf/core/db_manager/migration.rb

@@ -1,8 +1,8 @@
 # -*- coding: binary -*-
 module Msf::DBManager::Migration
-  # Loads Metasploit Data Models and adds its migrations to migrations paths.
+  # Loads Metasploit Data Models and adds gathers migration paths.
   #
-  # @return [void]
+  # @return Array[String]
   def add_rails_engine_migration_paths
     unless defined? ActiveRecord
       fail "Bundle installed '--without #{Bundler.settings.without.join(' ')}'.  To clear the without option do " \
@@ -10,20 +10,7 @@ module Msf::DBManager::Migration
            "the .bundle/config manually and then `bundle install`"
     end
 
-    ::Rails::Engine.subclasses.map(&:instance).each.each do |engine|
-      migrations_paths = engine.paths['db/migrate'].existent_directories
-
-      migrations_paths.each do |migrations_path|
-        # Since ActiveRecord::Migrator.migrations_paths can persist between
-        # instances of Msf::DBManager, such as in specs,
-        # migrations_path may already be part of
-        # migrations_paths, in which case it should not be added or multiple
-        # migrations with the same version number errors will occur.
-        unless ActiveRecord::Migrator.migrations_paths.include? migrations_path
-          ActiveRecord::Migrator.migrations_paths << migrations_path
-        end
-      end
-    end
+    gather_engine_migration_paths
   end
 
   # Migrate database to latest schema version.
@@ -47,8 +34,7 @@ module Msf::DBManager::Migration
     ActiveRecord::Migration.verbose = verbose
     ActiveRecord::Base.connection_pool.with_connection do
       begin
-        # When framework reached Rails 6 the path set here may be better suited a simple Array[]
-        context = ActiveRecord::MigrationContext.new(ActiveRecord::Migrator.migrations_paths)
+        context = ActiveRecord::MigrationContext.new(gather_engine_migration_paths)
         if context.needs_migration?
           ran = context.migrate
         end
@@ -81,6 +67,29 @@ module Msf::DBManager::Migration
 
   private
 
+  # Loads gathers migration paths from all loaded Rails engines.
+  #
+  # @return Array[String]
+  def gather_engine_migration_paths
+    paths = ActiveRecord::Migrator.migrations_paths
+
+    ::Rails::Engine.subclasses.map(&:instance).each.each do |engine|
+      migrations_paths = engine.paths['db/migrate'].existent_directories
+
+      migrations_paths.each do |migrations_path|
+        # Since ActiveRecord::Migrator.migrations_paths can persist between
+        # instances of Msf::DBManager, such as in specs,
+        # migrations_path may already be part of
+        # migrations_paths, in which case it should not be added or multiple
+        # migrations with the same version number errors will occur.
+        unless paths.include? migrations_path
+          paths << migrations_path
+        end
+      end
+    end
+    paths
+  end
+
   # Resets the column information for all descendants of ApplicationRecord
   # since some of the migrations may have cached column information that
   # has been updated by later migrations.

spec/support/shared/examples/msf/db_manager/migration.rb

@@ -12,16 +12,10 @@ RSpec.shared_examples_for 'Msf::DBManager::Migration' do
       db_manager.add_rails_engine_migration_paths
     end
 
-    it 'should not add duplicate paths to ActiveRecord::Migrator.migrations_paths' do
-      add_rails_engine_migration_paths
+    it 'should not add duplicate paths to gather_engine_migration_paths' do
+      paths = add_rails_engine_migration_paths
 
-      expect {
-        add_rails_engine_migration_paths
-      }.to_not change {
-        ActiveRecord::Migrator.migrations_paths.length
-      }
-
-      expect(ActiveRecord::Migrator.migrations_paths.uniq).to eq ActiveRecord::Migrator.migrations_paths
+      expect(add_rails_engine_migration_paths.uniq).to eq paths
     end
   end