Adds mergeRequestInteraction to GraphQL MemberInterface type

Closes https://gitlab.com/gitlab-org/gitlab/-/issues/329783

Changelog: added

app/graphql/types/member_interface.rb

@@ -25,6 +25,12 @@ module Types
     field :user, Types::UserType, null: true,
           description: 'User that is associated with the member object.'
 
+    field :merge_request_interaction, Types::UserMergeRequestInteractionType,
+          null: true,
+          description: 'Find a merge request.' do
+            argument :id, ::Types::GlobalIDType[::MergeRequest], required: true, description: 'Global ID of the merge request.'
+          end
+
     definition_methods do
       def resolve_type(object, context)
         case object
@@ -37,5 +43,11 @@ module Types
         end
       end
     end
+
+    def merge_request_interaction(id: nil)
+      Gitlab::Graphql::Lazy.with_value(GitlabSchema.object_from_id(id, expected_class: ::MergeRequest)) do |merge_request|
+        Users::MergeRequestInteraction.new(user: object.user, merge_request: merge_request) if merge_request
+      end
+    end
   end
 end

app/graphql/types/merge_requests/interacts_with_merge_request.rb

@@ -5,6 +5,8 @@ module Types
     module InteractsWithMergeRequest
       extend ActiveSupport::Concern
 
+      include FindClosest
+
       included do
         field :merge_request_interaction,
               type: ::Types::UserMergeRequestInteractionType,
@@ -13,8 +15,9 @@ module Types
               description: "Details of this user's interactions with the merge request."
       end
 
-      def merge_request_interaction(parent:)
+      def merge_request_interaction(parent:, id: nil)
         merge_request = closest_parent([::Types::MergeRequestType], parent)
+
         return unless merge_request
 
         Users::MergeRequestInteraction.new(user: object, merge_request: merge_request)

doc/api/graphql/reference/index.md

@@ -11360,6 +11360,20 @@ Represents a Group Membership.
 | <a id="groupmemberuser"></a>`user` | [`UserCore`](#usercore) | User that is associated with the member object. |
 | <a id="groupmemberuserpermissions"></a>`userPermissions` | [`GroupPermissions!`](#grouppermissions) | Permissions for the current user on the resource. |
 
+#### Fields with arguments
+
+##### `GroupMember.mergeRequestInteraction`
+
+Find a merge request.
+
+Returns [`UserMergeRequestInteraction`](#usermergerequestinteraction).
+
+###### Arguments
+
+| Name | Type | Description |
+| ---- | ---- | ----------- |
+| <a id="groupmembermergerequestinteractionid"></a>`id` | [`MergeRequestID!`](#mergerequestid) | Global ID of the merge request. |
+
 ### `GroupPermissions`
 
 #### Fields
@@ -14262,6 +14276,20 @@ Represents a Project Membership.
 | <a id="projectmemberuser"></a>`user` | [`UserCore`](#usercore) | User that is associated with the member object. |
 | <a id="projectmemberuserpermissions"></a>`userPermissions` | [`ProjectPermissions!`](#projectpermissions) | Permissions for the current user on the resource. |
 
+#### Fields with arguments
+
+##### `ProjectMember.mergeRequestInteraction`
+
+Find a merge request.
+
+Returns [`UserMergeRequestInteraction`](#usermergerequestinteraction).
+
+###### Arguments
+
+| Name | Type | Description |
+| ---- | ---- | ----------- |
+| <a id="projectmembermergerequestinteractionid"></a>`id` | [`MergeRequestID!`](#mergerequestid) | Global ID of the merge request. |
+
 ### `ProjectPermissions`
 
 #### Fields
@@ -18673,6 +18701,20 @@ Implementations:
 | <a id="memberinterfaceupdatedat"></a>`updatedAt` | [`Time`](#time) | Date and time the membership was last updated. |
 | <a id="memberinterfaceuser"></a>`user` | [`UserCore`](#usercore) | User that is associated with the member object. |
 
+##### Fields with arguments
+
+###### `MemberInterface.mergeRequestInteraction`
+
+Find a merge request.
+
+Returns [`UserMergeRequestInteraction`](#usermergerequestinteraction).
+
+####### Arguments
+
+| Name | Type | Description |
+| ---- | ---- | ----------- |
+| <a id="memberinterfacemergerequestinteractionid"></a>`id` | [`MergeRequestID!`](#mergerequestid) | Global ID of the merge request. |
+
 #### `NoteableInterface`
 
 Implementations:

spec/graphql/types/member_interface_spec.rb

@@ -12,6 +12,7 @@ RSpec.describe Types::MemberInterface do
       updated_at
       expires_at
       user
+      merge_request_interaction
     ]
 
     expect(described_class).to have_graphql_fields(*expected_fields)
@@ -40,4 +41,16 @@ RSpec.describe Types::MemberInterface do
       end
     end
   end
+
+  describe '#merge_request_interaction' do
+    subject { described_class.fields['mergeRequestInteraction'] }
+
+    it 'returns the correct type' do
+      is_expected.to have_graphql_type(Types::UserMergeRequestInteractionType)
+    end
+
+    it 'has the correct arguments' do
+      expect(subject.arguments).to have_key('id')
+    end
+  end
 end

spec/requests/api/graphql/project/project_members_spec.rb

@@ -110,6 +110,102 @@ RSpec.describe 'getting project members information' do
     end
   end
 
+  context 'merge request interactions' do
+    let(:project_path) { var('ID!').with(parent_project.full_path) }
+    let(:mr_a) do
+      var('MergeRequestID!')
+        .with(global_id_of(create(:merge_request, source_project: parent_project, source_branch: 'branch-1')))
+    end
+
+    let(:mr_b) do
+      var('MergeRequestID!')
+        .with(global_id_of(create(:merge_request, source_project: parent_project, source_branch: 'branch-2')))
+    end
+
+    let(:interaction_query) do
+      <<~HEREDOC
+      edges {
+        node {
+          user {
+            id
+          }
+          mrA: #{query_graphql_field(:merge_request_interaction, { id: mr_a }, 'canMerge')}
+        }
+      }
+      HEREDOC
+    end
+
+    let(:interaction_b_query) do
+      <<~HEREDOC
+      edges {
+        node {
+          user {
+            id
+          }
+          mrA: #{query_graphql_field(:merge_request_interaction, { id: mr_a }, 'canMerge')}
+          mrB: #{query_graphql_field(:merge_request_interaction, { id: mr_b }, 'canMerge')}
+        }
+      }
+      HEREDOC
+    end
+
+    it 'avoids N+1 queries, when requesting multiple MRs' do
+      control_query = with_signature(
+        [project_path, mr_a],
+        graphql_query_for(:project, { full_path: project_path },
+                          query_graphql_field(:project_members, nil, interaction_query))
+      )
+      query_two = with_signature(
+        [project_path, mr_a, mr_b],
+        graphql_query_for(:project, { full_path: project_path },
+                          query_graphql_field(:project_members, nil, interaction_b_query))
+      )
+
+      control_count = ActiveRecord::QueryRecorder.new do
+        post_graphql(control_query, current_user: user, variables: [project_path, mr_a])
+      end
+
+      # two project members, neither of whom can merge
+      expect(can_merge(:mrA)).to eq [false, false]
+
+      expect do
+        post_graphql(query_two, current_user: user, variables: [project_path, mr_a, mr_b])
+
+        expect(can_merge(:mrA)).to eq [false, false]
+        expect(can_merge(:mrB)).to eq [false, false]
+      end.not_to exceed_query_limit(control_count)
+    end
+
+    it 'avoids N+1 queries, when more users are involved' do
+      new_user = create(:user)
+
+      query = with_signature(
+        [project_path, mr_a],
+        graphql_query_for(:project, { full_path: project_path },
+                          query_graphql_field(:project_members, nil, interaction_query))
+      )
+
+      control_count = ActiveRecord::QueryRecorder.new do
+        post_graphql(query, current_user: user, variables: [project_path, mr_a])
+      end
+
+      # two project members, neither of whom can merge
+      expect(can_merge(:mrA)).to eq [false, false]
+
+      parent_project.add_guest(new_user)
+
+      expect do
+        post_graphql(query, current_user: user, variables: [project_path, mr_a])
+
+        expect(can_merge(:mrA)).to eq [false, false, false]
+      end.not_to exceed_query_limit(control_count)
+    end
+
+    def can_merge(name)
+      graphql_data_at(:project, :project_members, :edges, :node, name, :can_merge)
+    end
+  end
+
   context 'when unauthenticated' do
     it 'returns members' do
       fetch_members(current_user: nil, project: parent_project)