Add latest pipelines link to api

- Added latest_pipeline_for_ref method to project
- Updated pipelines_controller to use latest_pipeline_for_ref method
- Added api endpoint to pipelines api for latest pipeline

app/controllers/projects/pipelines_controller.rb

@@ -196,12 +196,7 @@ class Projects::PipelinesController < Projects::ApplicationController
   end
 
   def latest_pipeline
-    ref = params['ref'].presence || @project.default_branch
-    sha = @project.commit(ref)&.sha
-
-    @project.ci_pipelines
-            .newest_first(ref: ref, sha: sha)
-            .first
+    @project.latest_pipeline_for_ref(params['ref'])
             &.present(current_user: current_user)
   end
 

app/models/project.rb

@@ -752,6 +752,15 @@ class Project < ApplicationRecord
     latest_successful_build_for_ref(job_name, ref) || raise(ActiveRecord::RecordNotFound.new("Couldn't find job #{job_name}"))
   end
 
+  def latest_pipeline_for_ref(ref = default_branch)
+    ref = ref.presence || default_branch
+    sha = commit(ref)&.sha
+
+    return unless sha
+
+    ci_pipelines.newest_first(ref: ref, sha: sha).first
+  end
+
   def merge_base_commit(first_commit_id, second_commit_id)
     sha = repository.merge_base(first_commit_id, second_commit_id)
     commit_by(oid: sha) if sha

lib/api/pipelines.rb

@@ -69,6 +69,19 @@ module API
       end
       # rubocop: enable CodeReuse/ActiveRecord
 
+      desc 'Gets a the latest pipeline for the project branch' do
+        detail 'This feature was introduced in GitLab 12.3'
+        success Entities::Pipeline
+      end
+      params do
+        optional :ref, type: String, desc: 'branch ref of pipeline'
+      end
+      get ':id/pipelines/latest' do
+        authorize! :read_pipeline, latest_pipeline
+
+        present latest_pipeline, with: Entities::Pipeline
+      end
+
       desc 'Gets a specific pipeline for the project' do
         detail 'This feature was introduced in GitLab 8.11'
         success Entities::Pipeline
@@ -144,7 +157,15 @@ module API
 
     helpers do
       def pipeline
-        @pipeline ||= user_project.ci_pipelines.find(params[:pipeline_id])
+        strong_memoize(:pipeline) do
+          user_project.ci_pipelines.find(params[:pipeline_id])
+        end
+      end
+
+      def latest_pipeline
+        strong_memoize(:latest_pipeline) do
+          user_project.latest_pipeline_for_ref(params[:ref])
+        end
       end
     end
   end

spec/models/project_spec.rb

@@ -2027,6 +2027,43 @@ describe Project do
     end
   end
 
+  describe '#latest_pipeline_for_ref' do
+    let(:project) { create(:project, :repository) }
+    let(:second_branch) { project.repository.branches[2] }
+
+    let!(:pipeline_for_default_branch) do
+      create(:ci_empty_pipeline, project: project, sha: project.commit.id,
+                                 ref: project.default_branch)
+    end
+    let!(:pipeline_for_second_branch) do
+      create(:ci_empty_pipeline, project: project, sha: second_branch.target,
+                                 ref: second_branch.name)
+    end
+
+    before do
+      create(:ci_empty_pipeline, project: project, sha: project.commit.parent.id,
+                                 ref: project.default_branch)
+    end
+
+    context 'default repository branch' do
+      subject { project.latest_pipeline_for_ref(project.default_branch) }
+
+      it { is_expected.to eq(pipeline_for_default_branch) }
+    end
+
+    context 'provided ref' do
+      subject { project.latest_pipeline_for_ref(second_branch.name) }
+
+      it { is_expected.to eq(pipeline_for_second_branch) }
+    end
+
+    context 'bad ref' do
+      subject { project.latest_pipeline_for_ref(SecureRandom.uuid) }
+
+      it { is_expected.to be_nil }
+    end
+  end
+
   describe '#latest_successful_build_for_sha' do
     let(:project) { create(:project, :repository) }
     let(:pipeline) { create_pipeline(project) }

spec/requests/api/pipelines_spec.rb

@@ -459,6 +459,54 @@ describe API::Pipelines do
     end
   end
 
+  describe 'GET /projects/:id/pipelines/latest' do
+    context 'authorized user' do
+      let(:second_branch) { project.repository.branches[2] }
+
+      let!(:second_pipeline) do
+        create(:ci_empty_pipeline, project: project, sha: second_branch.target,
+                                   ref: second_branch.name, user: user)
+      end
+
+      before do
+        create(:ci_empty_pipeline, project: project, sha: project.commit.parent.id,
+                                   ref: project.default_branch, user: user)
+      end
+
+      context 'default repository branch' do
+        it 'gets the latest pipleine' do
+          get api("/projects/#{project.id}/pipelines/latest", user)
+
+          expect(response).to have_gitlab_http_status(200)
+          expect(response).to match_response_schema('public_api/v4/pipeline/detail')
+          expect(json_response['ref']).to eq(project.default_branch)
+          expect(json_response['sha']).to eq(project.commit.id)
+        end
+      end
+
+      context 'ref parameter' do
+        it 'gets the latest pipleine' do
+          get api("/projects/#{project.id}/pipelines/latest", user), params: { ref: second_branch.name }
+
+          expect(response).to have_gitlab_http_status(200)
+          expect(response).to match_response_schema('public_api/v4/pipeline/detail')
+          expect(json_response['ref']).to eq(second_branch.name)
+          expect(json_response['sha']).to eq(second_branch.target)
+        end
+      end
+    end
+
+    context 'unauthorized user' do
+      it 'does not return a project pipeline' do
+        get api("/projects/#{project.id}/pipelines/#{pipeline.id}", non_member)
+
+        expect(response).to have_gitlab_http_status(404)
+        expect(json_response['message']).to eq '404 Project Not Found'
+        expect(json_response['id']).to be nil
+      end
+    end
+  end
+
   describe 'GET /projects/:id/pipelines/:pipeline_id/variables' do
     subject { get api("/projects/#{project.id}/pipelines/#{pipeline.id}/variables", api_user) }