1 files changed, 82 insertions, 0 deletions
diff --git a/activerecord/lib/active_record/associations/builder/collection_association.rb b/activerecord/lib/active_record/associations/builder/collection_association.rb
new file mode 100644
index 0000000000..ff57c40121
--- /dev/null
+++ b/activerecord/lib/active_record/associations/builder/collection_association.rb
@@ -0,0 +1,82 @@
+# frozen_string_literal: true
+
+require "active_record/associations"
+
+module ActiveRecord::Associations::Builder # :nodoc:
+  class CollectionAssociation < Association #:nodoc:
+    CALLBACKS = [:before_add, :after_add, :before_remove, :after_remove]
+
+    def self.valid_options(options)
+      super + [:table_name, :before_add,
+               :after_add, :before_remove, :after_remove, :extend]
+    end
+
+    def self.define_callbacks(model, reflection)
+      super
+      name    = reflection.name
+      options = reflection.options
+      CALLBACKS.each { |callback_name|
+        define_callback(model, callback_name, name, options)
+      }
+    end
+
+    def self.define_extensions(model, name)
+      if block_given?
+        extension_module_name = "#{model.name.demodulize}#{name.to_s.camelize}AssociationExtension"
+        extension = Module.new(&Proc.new)
+        model.module_parent.const_set(extension_module_name, extension)
+      end
+    end
+
+    def self.define_callback(model, callback_name, name, options)
+      full_callback_name = "#{callback_name}_for_#{name}"
+
+      # TODO : why do i need method_defined? I think its because of the inheritance chain
+      model.class_attribute full_callback_name unless model.method_defined?(full_callback_name)
+      callbacks = Array(options[callback_name.to_sym]).map do |callback|
+        case callback
+        when Symbol
+          ->(method, owner, record) { owner.send(callback, record) }
+        when Proc
+          ->(method, owner, record) { callback.call(owner, record) }
+        else
+          ->(method, owner, record) { callback.send(method, owner, record) }
+        end
+      end
+      model.send "#{full_callback_name}=", callbacks
+    end
+
+    # Defines the setter and getter methods for the collection_singular_ids.
+    def self.define_readers(mixin, name)
+      super
+
+      mixin.class_eval <<-CODE, __FILE__, __LINE__ + 1
+        def #{name.to_s.singularize}_ids
+          association(:#{name}).ids_reader
+        end
+      CODE
+    end
+
+    def self.define_writers(mixin, name)
+      super
+
+      mixin.class_eval <<-CODE, __FILE__, __LINE__ + 1
+        def #{name.to_s.singularize}_ids=(ids)
+          association(:#{name}).ids_writer(ids)
+        end
+      CODE
+    end
+
+    def self.wrap_scope(scope, mod)
+      if scope
+        if scope.arity > 0
+          proc { |owner| instance_exec(owner, &scope).extending(mod) }
+        else
+          proc { instance_exec(&scope).extending(mod) }
+        end
+      else
+        proc { extending(mod) }
+      end
+    end
+  end
+end