Support custom .connection_extension

Author: rmosolgo

lib/graphql/schema/field.rb

@@ -14,6 +14,7 @@ class Field
       include GraphQL::Schema::Member::AcceptsDefinition
       include GraphQL::Schema::Member::HasArguments
       include GraphQL::Schema::Member::HasPath
+      extend GraphQL::Schema::FindInheritedValue
 
       # @return [String] the GraphQL name for this field, camelized unless `camelize: false` is provided
       attr_reader :name
@@ -135,6 +136,22 @@ def scoped?
         end
       end
 
+      # This extension is applied to fields when {#connection?} is true.
+      #
+      # You can override it in your base field definition.
+      # @return [Class] A {FieldExtension} subclass for implementing pagination behavior.
+      # @example Configuring a custom extension
+      #   class Types::BaseField < GraphQL::Schema::Field
+      #     connection_extension(MyCustomExtension)
+      #   end
+      def self.connection_extension(new_extension_class = nil)
+        if new_extension_class
+          @connection_extension = new_extension_class
+        else
+          @connection_extension ||= find_inherited_value(:connection_extension, ConnectionExtension)
+        end
+      end
+
       # @param name [Symbol] The underscore-cased version of this field name (will be camelized for the GraphQL API)
       # @param type [Class, GraphQL::BaseType, Array] The return type of this field
       # @param owner [Class] The type that this field belongs to
@@ -246,7 +263,7 @@ def initialize(type: nil, name: nil, owner: nil, null: nil, field: nil, function
         # The problem with putting this after the definition_block
         # is that it would override arguments
         if connection?
-          self.extension(ConnectionExtension)
+          self.extension(self.class.connection_extension)
         end
 
         if definition_block

spec/graphql/schema/field_spec.rb

@@ -349,4 +349,34 @@ def company(id:)
       assert_equal "1", res["data"]["company"]["id"]
     end
   end
+
+  describe ".connection_extension" do
+    class CustomConnectionExtension < GraphQL::Schema::Field::ConnectionExtension
+      def apply
+        super
+        field.argument(:z, String, required: false)
+      end
+    end
+
+    class CustomExtensionField < GraphQL::Schema::Field
+      connection_extension(CustomConnectionExtension)
+    end
+
+    class CustomExtensionObject < GraphQL::Schema::Object
+      field_class CustomExtensionField
+
+      field :ints, GraphQL::Types::Int.connection_type, null: false, scope: false
+    end
+
+    it "can be customized" do
+      field = CustomExtensionObject.fields["ints"]
+      assert_equal [CustomConnectionExtension], field.extensions.map(&:class)
+      assert_equal ["after", "before", "first", "last", "z"], field.arguments.keys.sort
+    end
+
+    it "can be inherited" do
+      child_field_class = Class.new(CustomExtensionField)
+      assert_equal CustomConnectionExtension, child_field_class.connection_extension
+    end
+  end
 end