DATABASE option for railties:install:migrations

activerecord/lib/active_record/railties/databases.rake

@@ -604,7 +604,7 @@ end
 
 namespace :railties do
   namespace :install do
-    # desc "Copy missing migrations from Railties (e.g. engines). You can specify Railties to use with FROM=railtie1,railtie2"
+    # desc "Copy missing migrations from Railties (e.g. engines). You can specify Railties to use with FROM=railtie1,railtie2 and database to copy to with DATABASE=database."
     task migrations: :'db:load_config' do
       to_load = ENV["FROM"].blank? ? :all : ENV["FROM"].split(",").map(&:strip)
       railties = {}
@@ -628,7 +628,16 @@ namespace :railties do
         puts "Copied migration #{migration.basename} from #{name}"
       end
 
-      ActiveRecord::Migration.copy(ActiveRecord::Tasks::DatabaseTasks.migrations_paths.first, railties,
+      if ENV["DATABASE"].present? && ENV["DATABASE"] != "primary"
+        config = ActiveRecord::Base.configurations.configs_for(name: ENV["DATABASE"])
+        raise "Invalid DATABASE provided" if config.blank?
+        destination = config.migrations_paths
+        raise "#{ENV["DATABASE"]} does not have a custom migration path" if destination.blank?
+      else
+        destination = ActiveRecord::Tasks::DatabaseTasks.migrations_paths.first
+      end
+
+      ActiveRecord::Migration.copy(destination, railties,
                                     on_skip: on_skip, on_copy: on_copy)
     end
   end

guides/source/engines.md

@@ -699,6 +699,18 @@ If you have multiple engines that need migrations copied over, use
 $ bin/rails railties:install:migrations
 ```
 
+You can specify a custom path in the source engine for the migrations by specifying MIGRATIONS_PATH.
+
+```bash
+$ bin/rails railties:install:migrations MIGRATIONS_PATH=db_blourgh
+```
+
+If you have multiple databases you can also specify the target database by specifying DATABASE.
+
+```bash
+$ bin/rails railties:install:migrations DATABASE=animals
+```
+
 This command, when run for the first time, will copy over all the migrations
 from the engine. When run the next time, it will only copy over migrations that
 haven't been copied over already. The first run for this command will output

railties/CHANGELOG.md

@@ -1,3 +1,14 @@
+*   Add `DATABASE` option to `railties:install:migrations`
+
+    This allows you to specify which database the migrations should be copied to
+    when running `rails railties:install:migrations`.
+
+    ```bash
+    $ rails railties:install:migrations DATABASE=animals
+    ```
+
+    *Matthew Hirst*
+
 *   The new method `config.autoload_lib(ignore:)` provides a simple way to
     autoload from `lib`:
 

railties/test/railties/engine_test.rb

@@ -10,7 +10,7 @@ class EngineTest < ActiveSupport::TestCase
     include Rack::Test::Methods
 
     def setup
-      build_app
+      build_app({ multi_db: true })
 
       @plugin = engine "bukkits" do |plugin|
         plugin.write "lib/bukkits.rb", <<-RUBY
@@ -32,8 +32,15 @@ def boot_rails
       require "#{app_path}/config/environment"
     end
 
-    def migrations
-      migration_root = File.expand_path(ActiveRecord::Migrator.migrations_paths.first, app_path)
+    def migrations(database = nil)
+      migration_path = if database
+        config = ActiveRecord::Base.configurations.configs_for(name: database)
+        config.migrations_paths
+      else
+        ActiveRecord::Migrator.migrations_paths.first
+      end
+
+      migration_root = File.expand_path(migration_path, app_path)
       sm = ActiveRecord::SchemaMigration::NullSchemaMigration.new
       im = ActiveRecord::InternalMetadata::NullInternalMetadata.new
       ActiveRecord::MigrationContext.new(migration_root, sm, im).migrations
@@ -117,6 +124,57 @@ def up
       end
     end
 
+    test "copying migrations to specific database" do
+      @plugin.write "db/migrate/1_create_users.rb", <<-RUBY
+        class CreateUsers < ActiveRecord::Migration::Current
+        end
+      RUBY
+
+      @plugin.write "db/migrate/2_add_last_name_to_users.rb", <<-RUBY
+        class AddLastNameToUsers < ActiveRecord::Migration::Current
+        end
+      RUBY
+
+      @plugin.write "db/migrate/3_create_sessions.rb", <<-RUBY
+        class CreateSessions < ActiveRecord::Migration::Current
+        end
+      RUBY
+
+      app_file "db/animals_migrate/1_create_sessions.rb", <<-RUBY
+        class CreateSessions < ActiveRecord::Migration::Current
+          def up
+          end
+        end
+      RUBY
+
+      restrict_frameworks
+      boot_rails
+
+      Dir.chdir(app_path) do
+        output = `bundle exec rake bukkits:install:migrations DATABASE=animals`
+
+        ["CreateUsers", "AddLastNameToUsers", "CreateSessions"].each do |migration_name|
+          assert migrations("animals").detect { |migration| migration.name == migration_name }
+        end
+        assert_match(/Copied migration \d+_create_users\.bukkits\.rb from bukkits/, output)
+        assert_match(/Copied migration \d+_add_last_name_to_users\.bukkits\.rb from bukkits/, output)
+        assert_match(/NOTE: Migration \d+_create_sessions\.rb from bukkits has been skipped/, output)
+
+        migrations_count = Dir["#{app_path}/db/animals_migrate/*.rb"].length
+
+        assert_equal migrations("animals").length, migrations_count
+
+        output = `bundle exec rake railties:install:migrations DATABASE=animals`.split("\n")
+
+        assert_equal migrations_count, Dir["#{app_path}/db/animals_migrate/*.rb"].length
+
+        assert_no_match(/\d+_create_users/, output.join("\n"))
+
+        bukkits_migration_order = output.index(output.detect { |o| /NOTE: Migration \d+_create_sessions\.rb from bukkits has been skipped/ =~ o })
+        assert_not_nil bukkits_migration_order, "Expected migration to be skipped"
+      end
+    end
+
     test "respects the order of railties when installing migrations" do
       @blog = engine "blog" do |plugin|
         plugin.write "lib/blog.rb", <<-RUBY