1 files changed, 108 insertions, 0 deletions
diff --git a/activemodel/lib/active_model/attributes.rb b/activemodel/lib/active_model/attributes.rb
new file mode 100644
index 0000000000..cac461b549
--- /dev/null
+++ b/activemodel/lib/active_model/attributes.rb
@@ -0,0 +1,108 @@
+# frozen_string_literal: true
+
+require "active_support/core_ext/object/deep_dup"
+require "active_model/attribute_set"
+require "active_model/attribute/user_provided_default"
+
+module ActiveModel
+  module Attributes #:nodoc:
+    extend ActiveSupport::Concern
+    include ActiveModel::AttributeMethods
+
+    included do
+      attribute_method_suffix "="
+      class_attribute :attribute_types, :_default_attributes, instance_accessor: false
+      self.attribute_types = Hash.new(Type.default_value)
+      self._default_attributes = AttributeSet.new({})
+    end
+
+    module ClassMethods
+      def attribute(name, type = Type::Value.new, **options)
+        name = name.to_s
+        if type.is_a?(Symbol)
+          type = ActiveModel::Type.lookup(type, **options.except(:default))
+        end
+        self.attribute_types = attribute_types.merge(name => type)
+        define_default_attribute(name, options.fetch(:default, NO_DEFAULT_PROVIDED), type)
+        define_attribute_methods(name)
+      end
+
+      private
+
+        def define_method_attribute=(name)
+          safe_name = name.unpack("h*".freeze).first
+          ActiveModel::AttributeMethods::AttrNames.set_name_cache safe_name, name
+
+          generated_attribute_methods.module_eval <<-STR, __FILE__, __LINE__ + 1
+            def __temp__#{safe_name}=(value)
+              name = ::ActiveModel::AttributeMethods::AttrNames::ATTR_#{safe_name}
+              write_attribute(name, value)
+            end
+            alias_method #{(name + '=').inspect}, :__temp__#{safe_name}=
+            undef_method :__temp__#{safe_name}=
+          STR
+        end
+
+        NO_DEFAULT_PROVIDED = Object.new # :nodoc:
+        private_constant :NO_DEFAULT_PROVIDED
+
+        def define_default_attribute(name, value, type)
+          self._default_attributes = _default_attributes.deep_dup
+          if value == NO_DEFAULT_PROVIDED
+            default_attribute = _default_attributes[name].with_type(type)
+          else
+            default_attribute = Attribute::UserProvidedDefault.new(
+              name,
+              value,
+              type,
+              _default_attributes.fetch(name.to_s) { nil },
+            )
+          end
+          _default_attributes[name] = default_attribute
+        end
+    end
+
+    def initialize(*)
+      @attributes = self.class._default_attributes.deep_dup
+      super
+    end
+
+    private
+
+      def write_attribute(attr_name, value)
+        name = if self.class.attribute_alias?(attr_name)
+          self.class.attribute_alias(attr_name).to_s
+        else
+          attr_name.to_s
+        end
+
+        @attributes.write_from_user(name, value)
+        value
+      end
+
+      def attribute(attr_name)
+        name = if self.class.attribute_alias?(attr_name)
+          self.class.attribute_alias(attr_name).to_s
+        else
+          attr_name.to_s
+        end
+        @attributes.fetch_value(name)
+      end
+
+      # Handle *= for method_missing.
+      def attribute=(attribute_name, value)
+        write_attribute(attribute_name, value)
+      end
+  end
+
+  module AttributeMethods #:nodoc:
+    AttrNames = Module.new {
+      def self.set_name_cache(name, value)
+        const_name = "ATTR_#{name}"
+        unless const_defined? const_name
+          const_set const_name, value.dup.freeze
+        end
+      end
+    }
+  end
+end