Added commit type to tree GraphQL type

app/graphql/types/commit_type.rb

+# frozen_string_literal: true
+
+module Types
+  class CommitType < BaseObject
+    graphql_name 'Commit'
+
+    authorize :download_code
+
+    present_using CommitPresenter
+
+    field :id, type: GraphQL::ID_TYPE, null: false
+    field :sha, type: GraphQL::STRING_TYPE, null: false
+    field :title, type: GraphQL::STRING_TYPE, null: true
+    field :description, type: GraphQL::STRING_TYPE, null: true
+    field :message, type: GraphQL::STRING_TYPE, null: true
+    field :authored_date, type: Types::TimeType, null: true
+    field :web_url, type: GraphQL::STRING_TYPE, null: false
+
+    # models/commit lazy loads the author by email
+    field :author, type: Types::UserType, null: true
+
+    field :latest_pipeline,
+          type: Types::Ci::PipelineType,
+          null: true,
+          description: "Latest pipeline for this commit",
+          resolve: -> (obj, ctx, args) do
+            Gitlab::Graphql::Loaders::PipelineForShaLoader.new(obj.project, obj.sha).find_last
+          end
+  end
+end

app/graphql/types/tree/tree_type.rb

@@ -4,6 +4,11 @@ module Types
     class TreeType < BaseObject
       graphql_name 'Tree'
 
+      # Complexity 10 as it triggers a Gitaly call on each render
+      field :last_commit, Types::CommitType, null: true, complexity: 10, resolve: -> (tree, args, ctx) do
+        tree.repository.last_commit_for_path(tree.sha, tree.path)
+      end
+
       field :trees, Types::Tree::TreeEntryType.connection_type, null: false, resolve: -> (obj, args, ctx) do
         Gitlab::Graphql::Representation::TreeEntry.decorate(obj.trees, obj.repository)
       end

app/models/ci/pipeline.rb

@@ -295,6 +295,11 @@ module Ci
       end
     end
 
+    def self.latest_for_shas(shas)
+      max_id_per_sha = for_sha(shas).group(:sha).select("max(id)")
+      where(id: max_id_per_sha)
+    end
+
     def self.latest_successful_ids_per_project
       success.group(:project_id).select('max(id) as id')
     end

app/presenters/commit_presenter.rb

 # frozen_string_literal: true
 
-class CommitPresenter < Gitlab::View::Presenter::Simple
+class CommitPresenter < Gitlab::View::Presenter::Delegated
+  include GlobalID::Identification
+
   presents :commit
 
   def status_for(ref)
@@ -10,4 +12,8 @@ class CommitPresenter < Gitlab::View::Presenter::Simple
   def any_pipelines?
     can?(current_user, :read_pipeline, commit.project) && commit.pipelines.any?
   end
+
+  def web_url
+    Gitlab::UrlBuilder.new(commit).url
+  end
 end

changelogs/unreleased/graphql-tree-last-commit.yml

+---
+title: Added commit type to tree GraphQL response
+merge_request: 29412
+author:
+type: added

lib/gitlab/graphql/loaders/pipeline_for_sha_loader.rb

+# frozen_string_literal: true
+
+module Gitlab
+  module Graphql
+    module Loaders
+      class PipelineForShaLoader
+        attr_accessor :project, :sha
+
+        def initialize(project, sha)
+          @project, @sha = project, sha
+        end
+
+        def find_last
+          BatchLoader.for(sha).batch(key: project) do |shas, loader, args|
+            pipelines = args[:key].ci_pipelines.latest_for_shas(shas)
+
+            pipelines.each do |pipeline|
+              loader.call(pipeline.sha, pipeline)
+            end
+          end
+        end
+      end
+    end
+  end
+end

spec/graphql/gitlab_schema_spec.rb

@@ -113,7 +113,7 @@ describe GitlabSchema do
     end
 
     it "raises a meaningful error if a global id couldn't be generated" do
-      expect { described_class.id_from_object(build(:commit)) }
+      expect { described_class.id_from_object(build(:wiki_directory)) }
         .to raise_error(RuntimeError, /include `GlobalID::Identification` into/i)
     end
   end

spec/graphql/types/commit_type_spec.rb

+# frozen_string_literal: true
+
+require 'spec_helper'
+
+describe GitlabSchema.types['Commit'] do
+  it { expect(described_class.graphql_name).to eq('Commit') }
+
+  it { expect(described_class).to require_graphql_authorizations(:download_code) }
+
+  it { expect(described_class).to have_graphql_fields(:id, :sha, :title, :description, :message, :authored_date, :author, :web_url, :latest_pipeline) }
+end

spec/graphql/types/tree/tree_type_spec.rb

@@ -5,5 +5,5 @@ require 'spec_helper'
 describe Types::Tree::TreeType do
   it { expect(described_class.graphql_name).to eq('Tree') }
 
-  it { expect(described_class).to have_graphql_fields(:trees, :submodules, :blobs) }
+  it { expect(described_class).to have_graphql_fields(:trees, :submodules, :blobs, :last_commit) }
 end

spec/lib/gitlab/graphql/loaders/pipeline_for_sha_loader_spec.rb

+require 'spec_helper'
+
+describe Gitlab::Graphql::Loaders::PipelineForShaLoader do
+  include GraphqlHelpers
+
+  describe '#find_last' do
+    it 'batch-resolves latest pipeline' do
+      project = create(:project, :repository)
+      pipeline1 = create(:ci_pipeline, project: project, ref: project.default_branch, sha: project.commit.sha)
+      pipeline2 = create(:ci_pipeline, project: project, ref: project.default_branch, sha: project.commit.sha)
+      pipeline3 = create(:ci_pipeline, project: project, ref: 'improve/awesome', sha: project.commit('improve/awesome').sha)
+
+      result = batch(max_queries: 1) do
+        [pipeline1.sha, pipeline3.sha].map { |sha| described_class.new(project, sha).find_last }
+      end
+
+      expect(result).to contain_exactly(pipeline2, pipeline3)
+    end
+  end
+end

spec/models/ci/pipeline_spec.rb

@@ -1886,6 +1886,17 @@ describe Ci::Pipeline, :mailer do
     end
   end
 
+  describe '.latest_for_shas' do
+    let(:sha) { 'abc' }
+
+    it 'returns latest pipeline for sha' do
+      create(:ci_pipeline, sha: sha)
+      pipeline2 = create(:ci_pipeline, sha: sha)
+
+      expect(described_class.latest_for_shas(sha)).to contain_exactly(pipeline2)
+    end
+  end
+
   describe '.latest_successful_ids_per_project' do
     let(:projects) { create_list(:project, 2) }
     let!(:pipeline1) { create(:ci_pipeline, :success, project: projects[0]) }

spec/requests/api/graphql/project/tree/tree_spec.rb

@@ -33,6 +33,12 @@ describe 'getting a tree in a project' do
       expect(graphql_data['project']['repository']['tree']['submodules']['edges']).to eq([])
       expect(graphql_data['project']['repository']['tree']['blobs']['edges']).to eq([])
     end
+
+    it 'returns null commit' do
+      post_graphql(query, current_user: current_user)
+
+      expect(graphql_data['project']['repository']['last_commit']).to be_nil
+    end
   end
 
   context 'when ref does not exist' do
@@ -45,6 +51,12 @@ describe 'getting a tree in a project' do
       expect(graphql_data['project']['repository']['tree']['submodules']['edges']).to eq([])
       expect(graphql_data['project']['repository']['tree']['blobs']['edges']).to eq([])
     end
+
+    it 'returns null commit' do
+      post_graphql(query, current_user: current_user)
+
+      expect(graphql_data['project']['repository']['last_commit']).to be_nil
+    end
   end
 
   context 'when ref and path exist' do
@@ -61,6 +73,12 @@ describe 'getting a tree in a project' do
       expect(graphql_data['project']['repository']['tree']['blobs']['edges'].size).to be > 0
       expect(graphql_data['project']['repository']['tree']['submodules']['edges'].size).to be > 0
     end
+
+    it 'returns tree latest commit' do
+      post_graphql(query, current_user: current_user)
+
+      expect(graphql_data['project']['repository']['tree']['lastCommit']).to be_present
+    end
   end
 
   context 'when current user is nil' do