Add POST project CI lint API endpoint

lib/api/lint.rb

@@ -46,5 +46,25 @@ module API
         present result, with: Entities::Ci::Lint::Result, current_user: current_user
       end
     end
+
+    resource :projects, requirements: API::NAMESPACE_OR_PROJECT_REQUIREMENTS do
+      desc 'Validation of .gitlab-ci.yml content' do
+        detail 'This feature was introduced in GitLab 13.6.'
+      end
+      params do
+        requires :content, type: String, desc: 'Content of .gitlab-ci.yml'
+        optional :dry_run, type: Boolean, default: false, desc: 'Run pipeline creation simulation, or only do static check.'
+      end
+      post ':id/ci/lint' do
+        authorize! :download_code, user_project
+
+        result = Gitlab::Ci::Lint
+          .new(project: user_project, current_user: current_user)
+          .validate(params[:content], dry_run: params[:dry_run])
+
+        status 200
+        present result, with: Entities::Ci::Lint::Result, current_user: current_user
+      end
+    end
   end
 end

spec/requests/api/lint_spec.rb

@@ -275,4 +275,167 @@ RSpec.describe API::Lint do
       end
     end
   end
+
+  describe 'POST /projects/:id/ci/lint' do
+    subject(:ci_lint) { post api("/projects/#{project.id}/ci/lint", api_user), params: { dry_run: dry_run, content: yaml_content } }
+
+    let(:project) { create(:project, :repository) }
+    let(:dry_run) { nil }
+
+    let_it_be(:api_user) { create(:user) }
+
+    let_it_be(:yaml_content) do
+      { include: { local: 'another-gitlab-ci.yml' }, test: { stage: 'test', script: 'echo 1' } }.to_yaml
+    end
+
+    let_it_be(:included_content) do
+      { another_test: { stage: 'test', script: 'echo 1' } }.to_yaml
+    end
+
+    RSpec.shared_examples 'valid project config' do
+      it 'passes validation' do
+        ci_lint
+
+        included_config = YAML.safe_load(included_content, [Symbol])
+        root_config = YAML.safe_load(yaml_content, [Symbol])
+        expected_yaml = included_config.merge(root_config).except(:include).to_yaml
+
+        expect(response).to have_gitlab_http_status(:ok)
+        expect(json_response).to be_an Hash
+        expect(json_response['merged_yaml']).to eq(expected_yaml)
+        expect(json_response['valid']).to eq(true)
+        expect(json_response['errors']).to eq([])
+      end
+    end
+
+    RSpec.shared_examples 'invalid project config' do
+      it 'responds with errors about invalid configuration' do
+        ci_lint
+
+        expect(response).to have_gitlab_http_status(:ok)
+        expect(json_response['merged_yaml']).to eq(yaml_content)
+        expect(json_response['valid']).to eq(false)
+        expect(json_response['errors']).to eq(['jobs config should contain at least one visible job'])
+      end
+    end
+
+    context 'when unauthenticated' do
+      let_it_be(:api_user) { nil }
+
+      it 'returns authentication error' do
+        ci_lint
+
+        expect(response).to have_gitlab_http_status(:not_found)
+      end
+    end
+
+    context 'when authenticated as non-member' do
+      context 'when project is private' do
+        before do
+          project.update!(visibility_level: Gitlab::VisibilityLevel::PRIVATE)
+        end
+
+        it 'returns authentication error' do
+          ci_lint
+
+          expect(response).to have_gitlab_http_status(:not_found)
+        end
+      end
+
+      context 'when project is public' do
+        before do
+          project.update!(visibility_level: Gitlab::VisibilityLevel::PUBLIC)
+        end
+
+        context 'when running as dry run' do
+          let(:dry_run) { true }
+
+          it 'returns pipeline creation error' do
+            ci_lint
+
+            expect(response).to have_gitlab_http_status(:ok)
+            expect(json_response['merged_yaml']).to eq(nil)
+            expect(json_response['valid']).to eq(false)
+            expect(json_response['errors']).to eq(['Insufficient permissions to create a new pipeline'])
+          end
+        end
+
+        context 'when running static validation' do
+          let(:dry_run) { false }
+
+          before do
+            project.repository.create_file(
+              project.creator,
+              'another-gitlab-ci.yml',
+              included_content,
+              message: 'Automatically created another-gitlab-ci.yml',
+              branch_name: 'master'
+            )
+          end
+
+          it_behaves_like 'valid project config'
+        end
+      end
+    end
+
+    context 'when authenticated as project guest' do
+      before do
+        project.add_guest(api_user)
+      end
+
+      it 'returns authentication error' do
+        ci_lint
+
+        expect(response).to have_gitlab_http_status(:forbidden)
+      end
+    end
+
+    context 'when authenticated as project developer' do
+      before do
+        project.add_developer(api_user)
+      end
+
+      context 'with valid .gitlab-ci.yml content' do
+        before do
+          project.repository.create_file(
+            project.creator,
+            'another-gitlab-ci.yml',
+            included_content,
+            message: 'Automatically created another-gitlab-ci.yml',
+            branch_name: 'master'
+          )
+        end
+
+        context 'when running as dry run' do
+          let(:dry_run) { true }
+
+          it_behaves_like 'valid project config'
+        end
+
+        context 'when running static validation' do
+          let(:dry_run) { false }
+
+          it_behaves_like 'valid project config'
+        end
+      end
+
+      context 'with invalid .gitlab-ci.yml content' do
+        let(:yaml_content) do
+          { image: 'ruby:2.7', services: ['postgres'] }.to_yaml
+        end
+
+        context 'when running as dry run' do
+          let(:dry_run) { true }
+
+          it_behaves_like 'invalid project config'
+        end
+
+        context 'when running static validation' do
+          let(:dry_run) { false }
+
+          it_behaves_like 'invalid project config'
+        end
+      end
+    end
+  end
 end