Port type_for_attribute to Active Model

This moves `type_for_attribute` from `ActiveRecord::ModelSchema::ClassMethods`
to `ActiveModel::AttributeRegistration::ClassMethods`, where
`attribute_types` is also defined.

Co-authored-by: Petrik <petrik@deheus.net>

activemodel/CHANGELOG.md

@@ -1,2 +1,17 @@
+*   Port the `type_for_attribute` method to Active Model. Classes that include
+    `ActiveModel::Attributes` will now provide this method. This method behaves
+    the same for Active Model as it does for Active Record.
+
+      ```ruby
+      class MyModel
+        include ActiveModel::Attributes
+
+        attribute :my_attribute, :integer
+      end
+
+      MyModel.type_for_attribute(:my_attribute) # => #<ActiveModel::Type::Integer ...>
+      ```
+
+    *Jonathan Hefner*
 
 Please check [7-1-stable](https://github.com/rails/rails/blob/7-1-stable/activemodel/CHANGELOG.md) for previous changes.

activemodel/lib/active_model/attribute_registration.rb

@@ -40,6 +40,21 @@ module ActiveModel
         end
       end
 
+      # Returns the type of the specified attribute after applying any
+      # modifiers. This method is the only valid source of information for
+      # anything related to the types of a model's attributes. The return value
+      # of this method will implement the interface described by
+      # ActiveModel::Type::Value (though the object itself may not subclass it).
+      def type_for_attribute(attribute_name, &block)
+        attribute_name = resolve_attribute_name(attribute_name)
+
+        if block
+          attribute_types.fetch(attribute_name, &block)
+        else
+          attribute_types[attribute_name]
+        end
+      end
+
       private
         PendingType = Struct.new(:name, :type) do # :nodoc:
           def apply_to(attribute_set)

activemodel/test/cases/attribute_registration_test.rb

@@ -73,6 +73,17 @@ module ActiveModel
       assert_equal Type::Value.new, klass.attribute_types["bar"]
     end
 
+    test ".type_for_attribute returns the registered attribute type" do
+      klass = class_with { attribute :foo, TYPE_1 }
+      assert_same TYPE_1, klass.type_for_attribute("foo")
+      assert_same TYPE_1, klass.type_for_attribute(:foo)
+    end
+
+    test ".type_for_attribute returns the default type when an unregistered attribute is specified" do
+      klass = class_with { attribute :foo, TYPE_1 }
+      assert_equal Type::Value.new, klass.type_for_attribute("bar")
+    end
+
     test "new attributes can be registered at any time" do
       klass = class_with { attribute :foo, TYPE_1 }
       assert_includes klass._default_attributes, "foo"

activemodel/test/cases/attributes_test.rb

@@ -175,5 +175,13 @@ module ActiveModel
         ModelForAttributesTest.attribute :foo, :unknown
       end
     end
+
+    test ".type_for_attribute supports attribute aliases" do
+      with_alias = Class.new(ModelForAttributesTest) do
+        alias_attribute :integer_field, :x
+      end
+
+      assert_equal with_alias.type_for_attribute(:integer_field), with_alias.type_for_attribute(:x)
+    end
   end
 end

activerecord/lib/active_record/attributes.rb

@@ -249,6 +249,15 @@ module ActiveRecord
         end
       end
 
+      ##
+      # :method: type_for_attribute
+      # :call-seq: type_for_attribute(attribute_name, &block)
+      #
+      # See ActiveModel::AttributeRegistration::ClassMethods#type_for_attribute.
+      #
+      # This method will access the database and load the model's schema if
+      # necessary.
+
       protected
         def reload_schema_from_cache(*)
           reset_default_attributes!

activerecord/lib/active_record/model_schema.rb

@@ -439,28 +439,6 @@ module ActiveRecord
         @yaml_encoder ||= ActiveModel::AttributeSet::YAMLEncoder.new(attribute_types)
       end
 
-      # Returns the type of the attribute with the given name, after applying
-      # all modifiers. This method is the only valid source of information for
-      # anything related to the types of a model's attributes. This method will
-      # access the database and load the model's schema if it is required.
-      #
-      # The return value of this method will implement the interface described
-      # by ActiveModel::Type::Value (though the object itself may not subclass
-      # it).
-      #
-      # +attr_name+ The name of the attribute to retrieve the type for. Must be
-      # a string or a symbol.
-      def type_for_attribute(attr_name, &block)
-        attr_name = attr_name.to_s
-        attr_name = attribute_aliases[attr_name] || attr_name
-
-        if block
-          attribute_types.fetch(attr_name, &block)
-        else
-          attribute_types[attr_name]
-        end
-      end
-
       # Returns the column object for the named attribute.
       # Returns an +ActiveRecord::ConnectionAdapters::NullColumn+ if the
       # named attribute does not exist.

activerecord/test/cases/attributes_test.rb

@@ -51,6 +51,14 @@ module ActiveRecord
       assert_equal 3, data.overloaded_float
     end
 
+    test ".type_for_attribute supports attribute aliases" do
+      with_alias = Class.new(OverloadedType) do
+        alias_attribute :overloaded_float, :x
+      end
+
+      assert_equal with_alias.type_for_attribute(:overloaded_float), with_alias.type_for_attribute(:x)
+    end
+
     test "overloaded properties with limit" do
       assert_equal 50, OverloadedType.type_for_attribute("overloaded_string_with_limit").limit
       assert_equal 255, UnoverloadedType.type_for_attribute("overloaded_string_with_limit").limit