More tests for concerning

activesupport/CHANGELOG.md

@@ -1,3 +1,23 @@
+*   Support `prepend` with `ActiveSupport::Concern`.
+
+    Allows a module with `extend ActiveSupport::Concern` to be prepended.
+
+        module Imposter
+          extend ActiveSupport::Concern
+
+          # Same as `included`, except only run when prepended.
+          prepended do
+          end
+        end
+
+        class Person
+          prepend Imposter
+        end
+
+    Concerning is also updated: `concerning :Imposter, prepend: true do`
+
+    *Jason Karns*
+
 *   Deprecate using `Range#include?` method to check the inclusion of a value
     in a date time range. It is recommended to use `Range#cover?` method
     instead of `Range#include?` to check the inclusion of a value

activesupport/lib/active_support/concern.rb

@@ -99,6 +99,14 @@ module ActiveSupport
   #   class Host
   #     include Bar # It works, now Bar takes care of its dependencies
   #   end
+  #
+  # === Prepending concerns
+  #
+  # Just like `include`, concerns also support `prepend` with a corresponding
+  # `prepended do` callback. `module ClassMethods` or `class_methods do` are
+  # still extended.
+  #
+  # `prepend` is also used for any dependencies.
   module Concern
     class MultipleIncludedBlocks < StandardError #:nodoc:
       def initialize

activesupport/lib/active_support/core_ext/module/concerning.rb

@@ -104,6 +104,11 @@ class Module
   # * grok the behavior of our class in one glance,
   # * clean up monolithic junk-drawer classes by separating their concerns, and
   # * stop leaning on protected/private for crude "this is internal stuff" modularity.
+  #
+  # === Prepending `concerning`
+  #
+  # `concerning` supports a `prepend: true` argument which will `prepend` the
+  # concern instead of using `include` for it.
   module Concerning
     # Define a new concern and mix it in.
     def concerning(topic, prepend: false, &block)

activesupport/test/core_ext/module/concerning_test.rb

@@ -7,6 +7,9 @@ class ModuleConcerningTest < ActiveSupport::TestCase
   def test_concerning_declares_a_concern_and_includes_it_immediately
     klass = Class.new { concerning(:Foo) { } }
     assert_includes klass.ancestors, klass::Foo, klass.ancestors.inspect
+
+    klass = Class.new { concerning(:Foo, prepend: true) { } }
+    assert_includes klass.ancestors, klass::Foo, klass.ancestors.inspect
   end
 
   def test_concerning_can_prepend_concern
@@ -27,6 +30,7 @@ class ModuleConcernTest < ActiveSupport::TestCase
     klass = Class.new do
       concern :Baz do
         included { @foo = 1 }
+        prepended { @foo = 2 }
         def should_be_public; end
       end
     end
@@ -42,6 +46,9 @@ class ModuleConcernTest < ActiveSupport::TestCase
 
     # Calls included hook
     assert_equal 1, Class.new { include klass::Baz }.instance_variable_get("@foo")
+
+    # Calls prepended hook
+    assert_equal 2, Class.new { prepend klass::Baz }.instance_variable_get("@foo")
   end
 
   class Foo
@@ -64,6 +71,26 @@ class ModuleConcernTest < ActiveSupport::TestCase
         def doesnt_clobber; end
       end
     end
+
+    concerning :Baz, prepend:true do
+      module ClassMethods
+        def will_be_orphaned_also; end
+      end
+
+      const_set :ClassMethods, Module.new {
+        def hacked_on_also; end
+      }
+
+      # Doesn't overwrite existing ClassMethods module.
+      class_methods do
+        def nicer_dsl_also; end
+      end
+
+      # Doesn't overwrite previous class_methods definitions.
+      class_methods do
+        def doesnt_clobber_also; end
+      end
+    end
   end
 
   def test_using_class_methods_blocks_instead_of_ClassMethods_module
@@ -76,4 +103,15 @@ class ModuleConcernTest < ActiveSupport::TestCase
     assert Foo.const_defined?(:ClassMethods)
     assert Foo::ClassMethods.method_defined?(:will_be_orphaned)
   end
+
+  def test_using_class_methods_blocks_instead_of_ClassMethods_module_prepend
+    assert_not_respond_to Foo, :will_be_orphaned_also
+    assert_respond_to Foo, :hacked_on_also
+    assert_respond_to Foo, :nicer_dsl_also
+    assert_respond_to Foo, :doesnt_clobber_also
+
+    # Orphan in Foo::ClassMethods, not Bar::ClassMethods.
+    assert Foo.const_defined?(:ClassMethods)
+    assert Foo::ClassMethods.method_defined?(:will_be_orphaned_also)
+  end
 end