From 65e0548d93bd5c0d382191e094f726775754d9b6 Mon Sep 17 00:00:00 2001
From: Ben Joyce <ben@hover.to>
Date: Wed, 8 Sep 2021 11:26:31 -0700
Subject: [PATCH] Add custom associations for fields

---
 Gemfile.lock                            |  2 +-
 README.md                               | 21 +++++++++++++++++++++
 lib/graphql/eager_load/builder.rb       | 12 ++++++++++++
 lib/graphql/eager_load/resolver.rb      |  2 +-
 lib/graphql/eager_load/version.rb       |  2 +-
 spec/graphql/eager_load_spec.rb         | 21 +++++++++++++++++++++
 spec/internal/app/graphql/types/user.rb |  7 +++++++
 7 files changed, 64 insertions(+), 3 deletions(-)

diff --git a/Gemfile.lock b/Gemfile.lock
index 2873c7a..1ec72c7 100644
--- a/Gemfile.lock
+++ b/Gemfile.lock
@@ -1,7 +1,7 @@
 PATH
   remote: .
   specs:
-    graphql-eager_load (0.2.2)
+    graphql-eager_load (0.2.3)
 
 GEM
   remote: https://rubygems.org/
diff --git a/README.md b/README.md
index 66d078a..d2b58d9 100644
--- a/README.md
+++ b/README.md
@@ -74,6 +74,27 @@ users {
 
 The output of the `#associations_to_eager_load` helper method would be `{estimates: {}, profile_photo: {blob: {}}`. Without the `.allow_include_builder_fields` class method the output would be `{estimates: {}}`.
 
+If you have a field that is derived from an association, but the association is not included in the query, you can define a `#custom_associations_for_fields` method to specify which associations to include for a specific field.
+
+```ruby
+module Types
+  class User < Types::Base
+    field :estimates, [Types::Estimate], null: false
+    field :org_names, [String], null: true
+    
+    def org_names
+      object.orgs.map(&:name)
+    end
+    
+    def self.custom_associations_for_fields
+      {
+        org_names: [:org]
+      }
+    end
+  end
+end
+```
+
 ## Development
 
 After checking out the repo, run `bundle` to install dependencies. Then, run `bundle exec rake spec` to run the tests. You can also run `bundle exec bin/console` for an interactive prompt that will allow you to experiment.
diff --git a/lib/graphql/eager_load/builder.rb b/lib/graphql/eager_load/builder.rb
index 7f80945..0abf7b0 100644
--- a/lib/graphql/eager_load/builder.rb
+++ b/lib/graphql/eager_load/builder.rb
@@ -42,6 +42,8 @@ def self.call(selections:, model:)
           else
             includes.merge!(builder.includes)
           end
+
+          includes.deep_merge!(builder.custom_associations_for_selection)
         end
       end
 
@@ -66,6 +68,16 @@ def active_storage_attachment?
         model.reflect_on_attachment(field_name).present?
       end
 
+      def custom_associations_for_selection
+        return {} unless field_owner.respond_to?(:custom_associations_for_fields)
+
+        custom_associations = field_owner.custom_associations_for_fields[field_name.to_sym]
+
+        return {} unless custom_associations
+
+        custom_associations.map { |association| [association, {}] }.to_h
+      end
+
       private
 
       attr_reader :selection, :model
diff --git a/lib/graphql/eager_load/resolver.rb b/lib/graphql/eager_load/resolver.rb
index fd01838..f04328c 100644
--- a/lib/graphql/eager_load/resolver.rb
+++ b/lib/graphql/eager_load/resolver.rb
@@ -12,7 +12,7 @@ def associations_to_include
         graphql_eager_load_options(model: self.class.class_variable_get(:@@eager_load_model))
       end
 
-      def graphql_eager_load_options(selections: context.query.lookahead.selections, model:)
+      def graphql_eager_load_options(model:, selections: context.query.lookahead.selections)
         Builder.call(selections: selections, model: model)
       end
 
diff --git a/lib/graphql/eager_load/version.rb b/lib/graphql/eager_load/version.rb
index 78e5226..3ee323e 100644
--- a/lib/graphql/eager_load/version.rb
+++ b/lib/graphql/eager_load/version.rb
@@ -2,6 +2,6 @@
 
 module Graphql
   module EagerLoad
-    VERSION = '0.2.2'
+    VERSION = '0.2.3'
   end
 end
diff --git a/spec/graphql/eager_load_spec.rb b/spec/graphql/eager_load_spec.rb
index 34fe01d..5ae1d4c 100644
--- a/spec/graphql/eager_load_spec.rb
+++ b/spec/graphql/eager_load_spec.rb
@@ -95,5 +95,26 @@
         )
       end
     end
+
+    describe 'custom_associations_for_fields' do
+      let(:model) { ::User }
+      let(:query_string) do
+        <<-QUERY
+        query {
+          users {
+            nodes {
+              email
+            }
+          }
+        }
+        QUERY
+      end
+
+      it 'includes the specified associations' do
+        expect(options).to eq(
+          jobs: {}
+        )
+      end
+    end
   end
 end
diff --git a/spec/internal/app/graphql/types/user.rb b/spec/internal/app/graphql/types/user.rb
index a788882..cf48c19 100644
--- a/spec/internal/app/graphql/types/user.rb
+++ b/spec/internal/app/graphql/types/user.rb
@@ -7,6 +7,7 @@ class User < GraphQL::Schema::Object
     field :proposal_documents, [ProposalDocument], null: false
     field :order, Order, null: false
     field :photo, Types::File, null: true
+    field :email, String, null: true
 
     def order
       { code: SecureRandom.uuid }
@@ -19,5 +20,11 @@ def photo
     def self.allow_include_builder_fields
       [:photo]
     end
+
+    def self.custom_associations_for_fields
+      {
+        email: [:jobs]
+      }
+    end
   end
 end