Use user_notes/discussions_count resolvers for MRs

Modify user_notes_count_resolver.rb and
user_discussions_count_resolver.rb to be generic
Use resolvers for MergeRequestType

app/graphql/resolvers/user_discussions_count_resolver.rb

@@ -9,8 +9,8 @@ module Resolvers
     def resolve
       authorize!(object)
 
-      BatchLoader::GraphQL.for(object.id).batch(key: :issue_user_discussions_count) do |ids, loader, args|
-        counts = Note.count_for_collection(ids, 'Issue', 'COUNT(DISTINCT discussion_id) as count').index_by(&:noteable_id)
+      BatchLoader::GraphQL.for(object.id).batch do |ids, loader, args|
+        counts = Note.count_for_collection(ids, object.class.name, 'COUNT(DISTINCT discussion_id) as count').index_by(&:noteable_id)
 
         ids.each do |id|
           loader.call(id, counts[id]&.count || 0)
@@ -19,7 +19,8 @@ module Resolvers
     end
 
     def authorized_resource?(object)
-      context[:current_user].present? && Ability.allowed?(context[:current_user], :read_issue, object)
+      ability = "read_#{object.class.name.underscore}".to_sym
+      context[:current_user].present? && Ability.allowed?(context[:current_user], ability, object)
     end
   end
 end

app/graphql/resolvers/user_notes_count_resolver.rb

@@ -9,8 +9,8 @@ module Resolvers
     def resolve
       authorize!(object)
 
-      BatchLoader::GraphQL.for(object.id).batch(key: :issue_user_notes_count) do |ids, loader, args|
-        counts = Note.count_for_collection(ids, 'Issue').index_by(&:noteable_id)
+      BatchLoader::GraphQL.for(object.id).batch(key: :user_notes_count) do |ids, loader, args|
+        counts = Note.count_for_collection(ids, object.class.name).index_by(&:noteable_id)
 
         ids.each do |id|
           loader.call(id, counts[id]&.count || 0)
@@ -19,7 +19,8 @@ module Resolvers
     end
 
     def authorized_resource?(object)
-      context[:current_user].present? && Ability.allowed?(context[:current_user], :read_issue, object)
+      ability = "read_#{object.class.name.underscore}".to_sym
+      context[:current_user].present? && Ability.allowed?(context[:current_user], ability, object)
     end
   end
 end

app/graphql/types/merge_request_type.rb

@@ -69,9 +69,11 @@ module Types
     field :merge_commit_sha, GraphQL::STRING_TYPE, null: true,
           description: 'SHA of the merge request commit (set once merged)'
     field :user_notes_count, GraphQL::INT_TYPE, null: true,
-          description: 'User notes count of the merge request'
+          description: 'User notes count of the merge request',
+          resolver: Resolvers::UserNotesCountResolver
     field :user_discussions_count, GraphQL::INT_TYPE, null: true,
-          description: 'Number of user discussions in the merge request'
+          description: 'Number of user discussions in the merge request',
+          resolver: Resolvers::UserDiscussionsCountResolver
     field :should_remove_source_branch, GraphQL::BOOLEAN_TYPE, method: :should_remove_source_branch?, null: true,
           description: 'Indicates if the source branch of the merge request will be deleted after merge'
     field :force_remove_source_branch, GraphQL::BOOLEAN_TYPE, method: :force_remove_source_branch?, null: true,

spec/graphql/resolvers/user_notes_count_resolver_spec.rb

@@ -7,18 +7,20 @@ RSpec.describe Resolvers::UserNotesCountResolver do
 
   describe '#resolve' do
     let_it_be(:user) { create(:user) }
-    let_it_be(:project) { create(:project, :public) }
-    let_it_be(:private_project) { create(:project, :private) }
+    let_it_be(:project) { create(:project, :repository, :public) }
+    let_it_be(:private_project) { create(:project, :repository, :private) }
+
+    specify do
+      expect(described_class).to have_nullable_graphql_type(GraphQL::INT_TYPE)
+    end
+
+    context 'when counting notes from an issue' do
       let_it_be(:issue) { create(:issue, project: project) }
       let_it_be(:private_issue) { create(:issue, project: private_project) }
       let_it_be(:public_notes) { create_list(:note, 2, noteable: issue, project: project) }
       let_it_be(:system_note) { create(:note, system: true, noteable: issue, project: project) }
       let_it_be(:private_notes) { create_list(:note, 3, noteable: private_issue, project: private_project) }
 
-    specify do
-      expect(described_class).to have_nullable_graphql_type(GraphQL::INT_TYPE)
-    end
-
       context 'when counting notes from a public issue' do
         subject { batch_sync { resolve_user_notes_count(issue) } }
 
@@ -48,6 +50,43 @@ RSpec.describe Resolvers::UserNotesCountResolver do
       end
     end
 
+    context 'when counting notes from a merge request' do
+      let_it_be(:merge_request) { create(:merge_request, source_project: project) }
+      let_it_be(:private_merge_request) { create(:merge_request, source_project: private_project) }
+      let_it_be(:public_notes) { create_list(:note, 2, noteable: merge_request, project: project) }
+      let_it_be(:system_note) { create(:note, system: true, noteable: merge_request, project: project) }
+      let_it_be(:private_notes) { create_list(:note, 3, noteable: private_merge_request, project: private_project) }
+
+      context 'when counting notes from a public merge request' do
+        subject { batch_sync { resolve_user_notes_count(merge_request) } }
+
+        it 'returns the number of non-system notes for the merge request' do
+          expect(subject).to eq(2)
+        end
+      end
+
+      context 'when a user has permission to view notes' do
+        before do
+          private_project.add_developer(user)
+        end
+
+        subject { batch_sync { resolve_user_notes_count(private_merge_request) } }
+
+        it 'returns the number of notes for the merge request' do
+          expect(subject).to eq(3)
+        end
+      end
+
+      context 'when a user does not have permission to view discussions' do
+        subject { batch_sync { resolve_user_notes_count(private_merge_request) } }
+
+        it 'returns no notes' do
+          expect { subject }.to raise_error(Gitlab::Graphql::Errors::ResourceNotAvailable)
+        end
+      end
+    end
+  end
+
   def resolve_user_notes_count(obj)
     resolve(described_class, obj: obj, ctx: { current_user: user })
   end