Features/1.10 ready

.gitignore

@@ -7,3 +7,4 @@
 /pkg/
 /spec/reports/
 /tmp/
+*.db

.ruby-version

@@ -1 +1 @@
-2.1.5
+2.5.8

graphql-preload.gemspec

@@ -22,13 +22,14 @@ Gem::Specification.new do |spec|
   spec.require_paths = ['lib']
 
   spec.add_runtime_dependency 'activerecord', '>= 4.1', '< 6'
-  spec.add_runtime_dependency 'graphql', '>= 1.8', '< 2'
-  spec.add_runtime_dependency 'graphql-batch', '~> 0.3'
+  spec.add_runtime_dependency 'graphql', '>= 1.9', '< 2'
+  spec.add_runtime_dependency 'graphql-batch', '~> 0.4'
   spec.add_runtime_dependency 'promise.rb', '~> 0.7'
 
-  spec.add_development_dependency 'bundler', '~> 1.16'
+  spec.add_development_dependency 'bundler', '~> 2.1'
   spec.add_development_dependency 'minitest', '~> 5.0'
-  spec.add_development_dependency 'pry', '~> 0.10'
+  spec.add_development_dependency 'pry-byebug', '~> 3.7'
   spec.add_development_dependency 'rake', '~> 10.0'
+  spec.add_development_dependency 'sqlite3', '~> 1.4'
   spec.add_development_dependency 'yard', '~> 0.9'
 end

lib/graphql/preload.rb

@@ -3,15 +3,15 @@
 require 'promise.rb'
 
 GraphQL::Field.accepts_definitions(
-  preload: ->(type, *args) do
+  preload: lambda do |type, *args|
     type.metadata[:preload] ||= []
     type.metadata[:preload].concat(args)
   end,
   preload_scope: ->(type, arg) { type.metadata[:preload_scope] = arg }
 )
 
 GraphQL::Schema.accepts_definitions(
-  enable_preloading: ->(schema) do
+  enable_preloading: lambda do |schema|
     schema.instrument(:field, GraphQL::Preload::Instrument.new)
   end
 )
@@ -20,6 +20,7 @@ module GraphQL
   # Provides a GraphQL::Field definition to preload ActiveRecord::Associations
   module Preload
     autoload :Instrument, 'graphql/preload/instrument'
+    autoload :FieldExtension, 'graphql/preload/field_extension'
     autoload :Loader, 'graphql/preload/loader'
     autoload :VERSION, 'graphql/preload/version'
 
@@ -30,21 +31,24 @@ def enable_preloading
     end
 
     module FieldMetadata
+      attr_reader :preload
+      attr_reader :preload_scope
+
       def initialize(*args, preload: nil, preload_scope: nil, **kwargs, &block)
         if preload
           @preload ||= []
           @preload.concat Array.wrap preload
         end
-        if preload_scope
-          @preload_scope = preload_scope
-        end
+
+        @preload_scope = preload_scope if preload_scope
+
         super(*args, **kwargs, &block)
       end
 
       def to_graphql
         field_defn = super
-        field_defn.metadata[:preload] = @preload
-        field_defn.metadata[:preload_scope] = @preload_scope
+        field_defn.metadata[:preload] = @preload if @preload
+        field_defn.metadata[:preload_scope] = @preload_scope if @preload_scope
         field_defn
       end
     end

lib/graphql/preload/field_extension.rb

@@ -0,0 +1,19 @@
+require 'graphql/preload/field_preloader'
+
+module GraphQL
+  module Preload
+    class FieldExtension < GraphQL::Schema::FieldExtension
+      include FieldPreloader
+
+      def resolve(object:, arguments:, context:)
+        yield(object, arguments) unless object
+
+        scope = field.preload_scope.call(arguments, context) if field.preload_scope
+
+        preload(object.object, options, scope).then do
+          yield(object, arguments)
+        end
+      end
+    end
+  end
+end

lib/graphql/preload/field_preloader.rb

@@ -0,0 +1,62 @@
+module GraphQL
+  module Preload
+    module FieldPreloader
+      private
+
+      def preload(record, associations, scope)
+        if associations.is_a?(String)
+          raise TypeError, "Expected #{associations} to be a Symbol, not a String"
+        elsif associations.is_a?(Symbol)
+          return preload_single_association(record, associations, scope)
+        end
+
+        promises = []
+
+        Array.wrap(associations).each do |association|
+          case association
+          when Symbol
+            promises << preload_single_association(record, association, scope)
+          when Array
+            association.each do |sub_association|
+              promises << preload(record, sub_association, scope)
+            end
+          when Hash
+            association.each do |sub_association, nested_association|
+              promises << preload_single_association(record, sub_association, scope).then do
+                associated_records = record.public_send(sub_association)
+
+                case associated_records
+                when ActiveRecord::Base
+                  preload(associated_records, nested_association, scope)
+                else
+                  Promise.all(
+                    Array.wrap(associated_records).map do |associated_record|
+                      preload(associated_record, nested_association, scope)
+                    end
+                  )
+                end
+              end
+            end
+          end
+        end
+
+        Promise.all(promises)
+      end
+
+      def preload_single_association(record, association, scope)
+        # We would like to pass the `scope` (which is an `ActiveRecord::Relation`),
+        # directly into `Loader.for`. However, because the scope is
+        # created for each parent record, they are different objects and
+        # return different loaders, breaking batching.
+        # Therefore, we pass in `scope.to_sql`, which is the same for all the
+        # scopes and set the `scope` using an accessor. The actual scope
+        # object used will be the last one, which shouldn't make any difference,
+        # because even though they are different objects, they are all
+        # functionally equivalent.
+        loader = GraphQL::Preload::Loader.for(record.class, association, scope.try(:to_sql))
+        loader.scope = scope
+        loader.load(record)
+      end
+    end
+  end
+end

lib/graphql/preload/instrument.rb

@@ -1,98 +1,33 @@
+require 'graphql/preload/field_preloader'
+
 module GraphQL
   module Preload
-    # Provides an instrument for the GraphQL::Field :preload definition
     class Instrument
-      def instrument(_type, field)
-        metadata = merged_metadata(field)
-        return field if metadata.fetch(:preload, nil).nil?
+      include FieldPreloader
 
-        old_resolver = field.resolve_proc
-        new_resolver = ->(obj, args, ctx) do
-          return old_resolver.call(obj, args, ctx) unless obj
-
-          if metadata[:preload_scope]
-            scope = metadata[:preload_scope].call(args, ctx)
-          end
-
-          is_graphql_object = obj.is_a?(GraphQL::Schema::Object)
-          respond_to_object = obj.respond_to?(:object)
-          record = is_graphql_object && respond_to_object ? obj.object : obj
-
-          preload(record, metadata[:preload], scope).then do
-            old_resolver.call(obj, args, ctx)
-          end
-        end
-
-        field.redefine do
-          resolve(new_resolver)
-        end
-      end
-
-      private def preload(record, associations, scope)
-        if associations.is_a?(String)
-          raise TypeError, "Expected #{associations} to be a Symbol, not a String"
-        elsif associations.is_a?(Symbol)
-          return preload_single_association(record, associations, scope)
-        end
+      def instrument(_type, field)
+        return field unless field.metadata.include?(:preload)
 
-        promises = []
+        if defined?(FieldExtension) && (type_class = field.metadata[:type_class])
+          type_class.extension(FieldExtension)
+          field
+        else
+          old_resolver = field.resolve_proc
+          new_resolver = lambda do |obj, args, ctx|
+            return old_resolver.call(obj, args, ctx) unless obj
 
-        Array.wrap(associations).each do |association|
-          case association
-          when Symbol
-            promises << preload_single_association(record, association, scope)
-          when Array
-            association.each do |sub_association|
-              promises << preload(record, sub_association, scope)
-            end
-          when Hash
-            association.each do |sub_association, nested_association|
-              promises << preload_single_association(record, sub_association, scope).then do
-                associated_records = record.public_send(sub_association)
+            scope = field.metadata[:preload_scope].call(args, ctx) if field.metadata[:preload_scope]
 
-                case associated_records
-                when ActiveRecord::Base
-                  preload(associated_records, nested_association, scope)
-                else
-                  Promise.all(
-                    Array.wrap(associated_records).map do |associated_record|
-                      preload(associated_record, nested_association, scope)
-                    end
-                  )
-                end
-              end
+            preload(obj.object, field.metadata[:preload], scope).then do
+              old_resolver.call(obj, args, ctx)
             end
           end
-        end
-
-        Promise.all(promises)
-      end
 
-      private def preload_single_association(record, association, scope)
-        # We would like to pass the `scope` (which is an `ActiveRecord::Relation`),
-        # directly into `Loader.for`. However, because the scope is
-        # created for each parent record, they are different objects and
-        # return different loaders, breaking batching.
-        # Therefore, we pass in `scope.to_sql`, which is the same for all the
-        # scopes and set the `scope` using an accessor. The actual scope
-        # object used will be the last one, which shouldn't make any difference,
-        # because even though they are different objects, they are all
-        # functionally equivalent.
-        loader = GraphQL::Preload::Loader.for(record.class, association, scope.try(:to_sql))
-        loader.scope = scope
-        loader.load(record)
-      end
-
-      private def merged_metadata(field)
-        type_class = field.metadata.fetch(:type_class, nil)
-
-        if type_class.nil? || !type_class.respond_to?(:to_graphql)
-          field.metadata
-        else
-          field.metadata.merge(type_class.to_graphql.metadata)
+          field.redefine do
+            resolve(new_resolver)
+          end
         end
       end
-
     end
   end
 end

lib/graphql/preload/loader.rb

@@ -22,6 +22,7 @@ def load(record)
         end
 
         return Promise.resolve(record) if association_loaded?(record)
+
         super
       end
 
@@ -30,31 +31,31 @@ def perform(records)
         records.each { |record| fulfill(record, record) }
       end
 
-      private def association_loaded?(record)
+      private
+
+      def association_loaded?(record)
         record.association(association).loaded?
       end
 
-      private def preload_association(records)
+      def preload_association(records)
         ActiveRecord::Associations::Preloader.new.preload(records, association, preload_scope)
       end
 
-      private def preload_scope
+      def preload_scope
         return nil unless scope
+
         reflection = model.reflect_on_association(association)
         raise ArgumentError, 'Cannot specify preload_scope for polymorphic associations' if reflection.polymorphic?
+
         scope if scope.try(:klass) == reflection.klass
       end
 
-      private def validate_association
-        unless association.is_a?(Symbol)
-          raise ArgumentError, 'Association must be a Symbol object'
-        end
-
-        unless model < ActiveRecord::Base
-          raise ArgumentError, 'Model must be an ActiveRecord::Base descendant'
-        end
+      def validate_association
+        raise ArgumentError, 'Association must be a Symbol object' unless association.is_a?(Symbol)
+        raise ArgumentError, "Model #{model} must be an ActiveRecord::Base descendant" unless model < ActiveRecord::Base
 
         return if model.reflect_on_association(association)
+
         raise TypeError, "Association :#{association} does not exist on #{model}"
       end
     end