Added new endpoint to Deployment API

Refactored merge request API params into module.
Leveraged MergeRequestHelpers in Deployment API.
Updated Deployment API documentation.

app/finders/merge_requests_finder.rb

@@ -39,6 +39,7 @@ class MergeRequestsFinder < IssuableFinder
 
   def filter_items(_items)
     items = by_commit(super)
+    items = by_deployment(items)
     items = by_source_branch(items)
     items = by_wip(items)
     items = by_target_branch(items)
@@ -101,6 +102,17 @@ class MergeRequestsFinder < IssuableFinder
         .or(table[:title].matches('WIP %'))
         .or(table[:title].matches('[WIP]%'))
   end
+
+  def by_deployment(items)
+    return items unless deployment_id
+
+    items.includes(:deployment_merge_requests)
+         .where(deployment_merge_requests: { deployment_id: deployment_id })
+  end
+
+  def deployment_id
+    @deployment_id ||= params[:deployment_id].presence
+  end
 end
 
 MergeRequestsFinder.prepend_if_ee('EE::MergeRequestsFinder')

changelogs/unreleased/35739-add-mr-to-deployment-api.yml

+---
+title: Add API support for retrieving merge requests deployed in a deployment
+merge_request: 21837
+author:
+type: added

doc/api/deployments.md

@@ -349,3 +349,19 @@ Example of a response:
   "deployable": null
 }
 ```
+
+## List of merge requests associated with a deployment
+
+> [Introduced](https://gitlab.com/gitlab-org/gitlab/issues/35739) in GitLab 12.7.
+
+This API retrieves the list of merge requests shipped with a given deployment:
+
+```
+GET /projects/:id/deployments/:deployment_id/merge_requests
+```
+
+It supports the same parameters as the [Merge Requests API](./merge_requests.md#list-merge-requests) and will return a response using the same format:
+
+```bash
+curl --header "PRIVATE-TOKEN: <your_access_token>" "https://gitlab.example.com/api/v4/projects/1/deployments/42"
+```

lib/api/deployments.rb

@@ -127,6 +127,26 @@ module API
           render_validation_error!(deployment)
         end
       end
+
+      helpers Helpers::MergeRequestsHelpers
+
+      desc 'Get all merge requests of a deployment' do
+        detail 'This feature was introduced in GitLab 12.7.'
+        success Entities::MergeRequestBasic
+      end
+      params do
+        requires :deployment_id, type: Integer, desc: 'The deployment ID'
+        use :merge_requests_base_params
+      end
+
+      get ':id/deployments/:deployment_id/merge_requests' do
+        authorize! :read_deployment, user_project
+
+        mr_params = declared_params.merge(deployment_id: params[:deployment_id])
+        merge_requests = MergeRequestsFinder.new(current_user, mr_params).execute
+
+        present merge_requests, { with: Entities::MergeRequestBasic, current_user: current_user }
+      end
     end
   end
 end

lib/api/helpers/merge_requests_helpers.rb

+# frozen_string_literal: true
+
+module API
+  module Helpers
+    module MergeRequestsHelpers
+      extend Grape::API::Helpers
+      include ::API::Helpers::CustomValidators
+
+      params :merge_requests_base_params do
+        optional :state,
+                 type: String,
+                 values: %w[opened closed locked merged all],
+                 default: 'all',
+                 desc: 'Return opened, closed, locked, merged, or all merge requests'
+        optional :order_by,
+                 type: String,
+                 values: %w[created_at updated_at],
+                 default: 'created_at',
+                 desc: 'Return merge requests ordered by `created_at` or `updated_at` fields.'
+        optional :sort,
+                 type: String,
+                 values: %w[asc desc],
+                 default: 'desc',
+                 desc: 'Return merge requests sorted in `asc` or `desc` order.'
+        optional :milestone, type: String, desc: 'Return merge requests for a specific milestone'
+        optional :labels,
+                 type: Array[String],
+                 coerce_with: Validations::Types::LabelsList.coerce,
+                 desc: 'Comma-separated list of label names'
+        optional :with_labels_details, type: Boolean, desc: 'Return titles of labels and other details', default: false
+        optional :created_after, type: DateTime, desc: 'Return merge requests created after the specified time'
+        optional :created_before, type: DateTime, desc: 'Return merge requests created before the specified time'
+        optional :updated_after, type: DateTime, desc: 'Return merge requests updated after the specified time'
+        optional :updated_before, type: DateTime, desc: 'Return merge requests updated before the specified time'
+        optional :view,
+                 type: String,
+                 values: %w[simple],
+                 desc: 'If simple, returns the `iid`, URL, title, description, and basic state of merge request'
+        optional :author_id, type: Integer, desc: 'Return merge requests which are authored by the user with the given ID'
+        optional :assignee_id,
+                 types: [Integer, String],
+                 integer_none_any: true,
+                 desc: 'Return merge requests which are assigned to the user with the given ID'
+        optional :scope,
+                 type: String,
+                 values: %w[created-by-me assigned-to-me created_by_me assigned_to_me all],
+                 desc: 'Return merge requests for the given scope: `created_by_me`, `assigned_to_me` or `all`'
+        optional :my_reaction_emoji, type: String, desc: 'Return issues reacted by the authenticated user by the given emoji'
+        optional :source_branch, type: String, desc: 'Return merge requests with the given source branch'
+        optional :source_project_id, type: Integer, desc: 'Return merge requests with the given source project id'
+        optional :target_branch, type: String, desc: 'Return merge requests with the given target branch'
+        optional :search,
+                 type: String,
+                 desc: 'Search merge requests for text present in the title, description, or any combination of these'
+        optional :in, type: String, desc: '`title`, `description`, or a string joining them with comma'
+        optional :wip, type: String, values: %w[yes no], desc: 'Search merge requests for WIP in the title'
+      end
+
+      params :optional_scope_param do
+        optional :scope,
+                 type: String,
+                 values: %w[created-by-me assigned-to-me created_by_me assigned_to_me all],
+                 default: 'created_by_me',
+                 desc: 'Return merge requests for the given scope: `created_by_me`, `assigned_to_me` or `all`'
+      end
+    end
+  end
+end

lib/api/merge_requests.rb

@@ -7,6 +7,7 @@ module API
     before { authenticate_non_get! }
 
     helpers ::Gitlab::IssuableMetadata
+    helpers Helpers::MergeRequestsHelpers
 
     # EE::API::MergeRequests would override the following helpers
     helpers do
@@ -107,33 +108,7 @@ module API
       end
 
       params :merge_requests_params do
-        optional :state, type: String, values: %w[opened closed locked merged all], default: 'all',
-                         desc: 'Return opened, closed, locked, merged, or all merge requests'
-        optional :order_by, type: String, values: %w[created_at updated_at], default: 'created_at',
-                            desc: 'Return merge requests ordered by `created_at` or `updated_at` fields.'
-        optional :sort, type: String, values: %w[asc desc], default: 'desc',
-                        desc: 'Return merge requests sorted in `asc` or `desc` order.'
-        optional :milestone, type: String, desc: 'Return merge requests for a specific milestone'
-        optional :labels, type: Array[String], coerce_with: Validations::Types::LabelsList.coerce, desc: 'Comma-separated list of label names'
-        optional :with_labels_details, type: Boolean, desc: 'Return titles of labels and other details', default: false
-        optional :created_after, type: DateTime, desc: 'Return merge requests created after the specified time'
-        optional :created_before, type: DateTime, desc: 'Return merge requests created before the specified time'
-        optional :updated_after, type: DateTime, desc: 'Return merge requests updated after the specified time'
-        optional :updated_before, type: DateTime, desc: 'Return merge requests updated before the specified time'
-        optional :view, type: String, values: %w[simple], desc: 'If simple, returns the `iid`, URL, title, description, and basic state of merge request'
-        optional :author_id, type: Integer, desc: 'Return merge requests which are authored by the user with the given ID'
-        optional :assignee_id, types: [Integer, String], integer_none_any: true,
-                               desc: 'Return merge requests which are assigned to the user with the given ID'
-        optional :scope, type: String, values: %w[created-by-me assigned-to-me created_by_me assigned_to_me all],
-                         desc: 'Return merge requests for the given scope: `created_by_me`, `assigned_to_me` or `all`'
-        optional :my_reaction_emoji, type: String, desc: 'Return issues reacted by the authenticated user by the given emoji'
-        optional :source_branch, type: String, desc: 'Return merge requests with the given source branch'
-        optional :source_project_id, type: Integer, desc: 'Return merge requests with the given source project id'
-        optional :target_branch, type: String, desc: 'Return merge requests with the given target branch'
-        optional :search, type: String, desc: 'Search merge requests for text present in the title, description, or any combination of these'
-        optional :in, type: String, desc: '`title`, `description`, or a string joining them with comma'
-        optional :wip, type: String, values: %w[yes no], desc: 'Search merge requests for WIP in the title'
-
+        use :merge_requests_base_params
         use :optional_merge_requests_search_params
         use :pagination
       end
@@ -145,8 +120,7 @@ module API
       end
       params do
         use :merge_requests_params
-        optional :scope, type: String, values: %w[created-by-me assigned-to-me created_by_me assigned_to_me all], default: 'created_by_me',
-                         desc: 'Return merge requests for the given scope: `created_by_me`, `assigned_to_me` or `all`'
+        use :optional_scope_param
       end
       get do
         authenticate! unless params[:scope] == 'all'

spec/finders/merge_requests_finder_spec.rb

@@ -166,6 +166,38 @@ describe MergeRequestsFinder do
 
           expect(scalar_params).to include(:wip, :assignee_id)
         end
+
+        context 'filter by deployment' do
+          let_it_be(:project_with_repo) { create(:project, :repository) }
+
+          it 'returns the relevant merge requests' do
+            deployment1 = create(
+              :deployment,
+              project: project_with_repo,
+              sha: project_with_repo.commit.id,
+              merge_requests: [merge_request1, merge_request2]
+            )
+            create(
+              :deployment,
+              project: project_with_repo,
+              sha: project_with_repo.commit.id,
+              merge_requests: [merge_request3]
+            )
+            params = { deployment_id: deployment1.id }
+            merge_requests = described_class.new(user, params).execute
+
+            expect(merge_requests).to contain_exactly(merge_request1, merge_request2)
+          end
+
+          context 'when a deployment does not contain any merge requests' do
+            it 'returns an empty result' do
+              params = { deployment_id: create(:deployment, project: project_with_repo, sha: project_with_repo.commit.sha).id }
+              merge_requests = described_class.new(user, params).execute
+
+              expect(merge_requests).to be_empty
+            end
+          end
+        end
       end
 
       context 'assignee filtering' do

spec/requests/api/deployments_spec.rb

@@ -343,6 +343,48 @@ describe API::Deployments do
     end
   end
 
+  describe 'GET /projects/:id/deployments/:deployment_id/merge_requests' do
+    let(:project) { create(:project, :repository) }
+    let!(:deployment) { create(:deployment, :success, project: project) }
+
+    subject { get api("/projects/#{project.id}/deployments/#{deployment.id}/merge_requests", user) }
+
+    context 'when a user is not a member of the deployment project' do
+      let(:user) { build(:user) }
+
+      it 'returns a 404 status code' do
+        subject
+
+        expect(response).to have_gitlab_http_status(404)
+      end
+    end
+
+    context 'when a user member of the deployment project' do
+      let_it_be(:project2) { create(:project) }
+      let!(:merge_request1) { create(:merge_request, source_project: project, target_project: project) }
+      let!(:merge_request2) { create(:merge_request, source_project: project, target_project: project, state: 'closed') }
+      let!(:merge_request3) { create(:merge_request, source_project: project2, target_project: project2) }
+
+      it 'returns the relevant merge requests linked to a deployment for a project' do
+        deployment.merge_requests << [merge_request1, merge_request2]
+
+        subject
+
+        expect(response).to have_gitlab_http_status(200)
+        expect(json_response.map { |d| d['id'] }).to contain_exactly(merge_request1.id, merge_request2.id)
+      end
+
+      context 'when a deployment is not associated to any existing merge requests' do
+        it 'returns an empty array' do
+          subject
+
+          expect(response).to have_gitlab_http_status(200)
+          expect(json_response).to eq([])
+        end
+      end
+    end
+  end
+
   context 'prevent N + 1 queries' do
     context 'when the endpoint returns multiple records' do
       let(:project) { create(:project, :repository) }