Merge pull request #32 from exAspArk/graphql

Make BatchLoader work with the latest GraphQL versions

Author: exAspArk

README.md

@@ -258,13 +258,13 @@ query = "
 Schema.execute(query)
 ```
 
-To avoid this problem, all we have to do is to change the resolver to return `BatchLoader`:
+To avoid this problem, all we have to do is to change the resolver to return `BatchLoader::GraphQL` ([#32](https://github.com/exAspArk/batch-loader/pull/32) explains why not just `BatchLoader`):
 
 ```ruby
 PostType = GraphQL::ObjectType.define do
   name "Post"
   field :user, !UserType, resolve: ->(post, args, ctx) do
-    BatchLoader.for(post.user_id).batch do |user_ids, loader|
+    BatchLoader::GraphQL.for(post.user_id).batch do |user_ids, loader|
       User.where(id: user_ids).each { |user| loader.call(user.id, user) }
     end
   end

lib/batch_loader/graphql.rb

@@ -2,29 +2,45 @@
 
 class BatchLoader
   class GraphQL
-    class Wrapper
-      def initialize(batch_loader)
-        @batch_loader = batch_loader
-      end
-
-      def sync
-        @batch_loader.__sync
-      end
-    end
-
     def self.use(schema_definition)
-      schema_definition.lazy_resolve(BatchLoader::GraphQL::Wrapper, :sync)
+      schema_definition.lazy_resolve(BatchLoader::GraphQL, :sync)
+      # for graphql gem versions <= 1.8.6 which work with BatchLoader instead of BatchLoader::GraphQL
       schema_definition.instrument(:field, self)
     end
 
     def self.instrument(type, field)
       old_resolve_proc = field.resolve_proc
       new_resolve_proc = ->(object, arguments, context) do
         result = old_resolve_proc.call(object, arguments, context)
-        result.respond_to?(:__sync) ? BatchLoader::GraphQL::Wrapper.new(result) : result
+        result.respond_to?(:__sync) ? BatchLoader::GraphQL.wrap(result) : result
       end
 
       field.redefine { resolve(new_resolve_proc) }
     end
+
+    def self.wrap(batch_loader)
+      BatchLoader::GraphQL.new.tap do |graphql|
+        graphql.batch_loader = batch_loader
+      end
+    end
+
+    def self.for(item)
+      new(item)
+    end
+
+    attr_writer :batch_loader
+
+    def initialize(item = nil)
+      @batch_loader = BatchLoader.for(item)
+    end
+
+    def batch(*args, &block)
+      @batch_loader.batch(*args, &block)
+      self
+    end
+
+    def sync
+      @batch_loader.__sync
+    end
   end
 end

spec/fixtures/graphql_schema.rb

@@ -7,10 +7,15 @@
 
   PostType = GraphQL::ObjectType.define do
     name "Post"
-    field :user, !UserType, resolve: ->(object, args, ctx) { object.user_lazy }
-    field :userId, !types.Int, resolve: ->(object, args, ctx) do
-      BatchLoader.for(object).batch do |posts, loader|
-        posts.each { |p| loader.call(p, p.user_lazy.id) }
+    field :user, !UserType, resolve: ->(object, args, ctx) do
+      BatchLoader::GraphQL.for(object.user_id).batch do |user_ids, loader|
+        User.where(id: user_ids).each { |user| loader.call(user.id, user) }
+      end
+    end
+
+    field :userOld, !UserType, resolve: ->(object, args, ctx) do
+      BatchLoader.for(object.user_id).batch do |user_ids, loader|
+        User.where(id: user_ids).each { |user| loader.call(user.id, user) }
       end
     end
   end
@@ -31,15 +36,17 @@ class UserType < GraphQL::Schema::Object
 
   class PostType < GraphQL::Schema::Object
     field :user, UserType, null: false
-    field :user_id, Int, null: false
+    field :user_old, UserType, null: false
 
     def user
-      object.user_lazy
+      BatchLoader::GraphQL.for(object.user_id).batch do |user_ids, loader|
+        User.where(id: user_ids).each { |user| loader.call(user.id, user) }
+      end
     end
 
-    def user_id
-      BatchLoader.for(object).batch do |posts, loader|
-        posts.each { |p| loader.call(p, p.user_lazy.id) }
+    def user_old
+      BatchLoader.for(object.user_id).batch do |user_ids, loader|
+        User.where(id: user_ids).each { |user| loader.call(user.id, user) }
       end
     end
   end

spec/fixtures/models.rb

@@ -84,7 +84,6 @@ def eql?(other)
   private
 
   def some_private_method
-    :some_private_method
   end
 end
 

spec/graphql_spec.rb

@@ -10,19 +10,19 @@
       {
         posts {
           user { id }
-          userId
+          userOld { id }
         }
       }
     QUERY
 
-    expect(User).to receive(:where).with(id: ["1", "2"]).once.and_call_original
+    expect(User).to receive(:where).with(id: ["1", "2"]).twice.and_call_original
 
     result = GraphqlSchema.execute(query)
 
     expect(result['data']).to eq({
       'posts' => [
-        {'user' => {'id' => "1"}, "userId" => 1},
-        {'user' => {'id' => "2"}, "userId" => 2}
+        {'user' => {'id' => "1"}, 'userOld' => {'id' => "1"}},
+        {'user' => {'id' => "2"}, 'userOld' => {'id' => "2"}}
       ]
     })
   end