Feature: delegate all open discussions to Issue

When a merge request can only be merged when all discussions are
resolved. This feature allows to easily delegate those discussions to a
new issue, while marking them as resolved in the merge request.

The user is presented with a new issue, prepared with mentions of all
unresolved discussions, including the first unresolved note of the
discussion, time and link to the note.

When the issue is created, the discussions in the merge request will get
a system note directing the user to the newly created issue.

app/controllers/projects/discussions_controller.rb

@@ -5,9 +5,7 @@ class Projects::DiscussionsController < Projects::ApplicationController
   before_action :authorize_resolve_discussion!
 
   def resolve
-    discussion.resolve!(current_user)
-
-    MergeRequests::ResolvedDiscussionNotificationService.new(project, current_user).execute(merge_request)
+    Discussions::ResolveService.new(project, current_user, merge_request: merge_request).execute(discussion)
 
     render json: {
       resolved_by: discussion.resolved_by.try(:name),

app/controllers/projects/issues_controller.rb

@@ -46,8 +46,9 @@ class Projects::IssuesController < Projects::ApplicationController
     params[:issue] ||= ActionController::Parameters.new(
       assignee_id: ""
     )
+    build_params = issue_params.merge(merge_request_for_resolving_discussions: merge_request_for_resolving_discussions)
+    @issue = @noteable = Issues::BuildService.new(project, current_user, build_params).execute
 
-    @issue = @noteable = @project.issues.new(issue_params)
     respond_with(@issue)
   end
 
@@ -75,7 +76,9 @@ class Projects::IssuesController < Projects::ApplicationController
   end
 
   def create
-    @issue = Issues::CreateService.new(project, current_user, issue_params.merge(request: request)).execute
+    extra_params = { request: request,
+                     merge_request_for_resolving_discussions: merge_request_for_resolving_discussions }
+    @issue = Issues::CreateService.new(project, current_user, issue_params.merge(extra_params)).execute
 
     respond_to do |format|
       format.html do
@@ -169,6 +172,14 @@ class Projects::IssuesController < Projects::ApplicationController
   alias_method :awardable, :issue
   alias_method :spammable, :issue
 
+  def merge_request_for_resolving_discussions
+    return unless merge_request_iid = params[:merge_request_for_resolving_discussions]
+
+    @merge_request_for_resolving_discussions ||= MergeRequestsFinder.new(current_user, project_id: project.id).
+                                                   execute.
+                                                   find_by(iid: merge_request_iid)
+  end
+
   def authorize_read_issue!
     return render_404 unless can?(current_user, :read_issue, @issue)
   end

app/models/discussion.rb

@@ -88,6 +88,10 @@ class Discussion
     @first_note ||= @notes.first
   end
 
+  def first_note_to_resolve
+    @first_note_to_resolve ||= notes.detect(&:to_be_resolved?)
+  end
+
   def last_note
     @last_note ||= @notes.last
   end

app/models/merge_request.rb

@@ -480,6 +480,14 @@ class MergeRequest < ActiveRecord::Base
     @diff_discussions ||= self.notes.diff_notes.discussions
   end
 
+  def resolvable_discussions
+    @resolvable_discussions ||= diff_discussions.select(&:to_be_resolved?)
+  end
+
+  def discussions_can_be_resolved_by?(user)
+    resolvable_discussions.all? { |discussion| discussion.can_resolve?(user) }
+  end
+
   def find_diff_discussion(discussion_id)
     notes = self.notes.diff_notes.where(discussion_id: discussion_id).fresh.to_a
     return if notes.empty?

app/models/note.rb

@@ -99,7 +99,7 @@ class Note < ActiveRecord::Base
     end
 
     def discussions
-      Discussion.for_notes(all)
+      Discussion.for_notes(fresh)
     end
 
     def grouped_diff_discussions

app/services/discussions/base_service.rb

+module Discussions
+  class BaseService < ::BaseService
+  end
+end

app/services/discussions/resolve_service.rb

+module Discussions
+  class ResolveService < Discussions::BaseService
+    def execute(one_or_more_discussions)
+      Array(one_or_more_discussions).each { |discussion| resolve_discussion(discussion) }
+    end
+
+    def resolve_discussion(discussion)
+      return unless discussion.can_resolve?(current_user)
+
+      discussion.resolve!(current_user)
+
+      MergeRequests::ResolvedDiscussionNotificationService.new(project, current_user).execute(merge_request)
+      SystemNoteService.discussion_continued_in_issue(discussion, project, current_user, follow_up_issue) if follow_up_issue
+    end
+
+    def merge_request
+      params[:merge_request]
+    end
+
+    def follow_up_issue
+      params[:follow_up_issue]
+    end
+  end
+end

app/services/issuable_base_service.rb

@@ -122,7 +122,8 @@ class IssuableBaseService < BaseService
       SlashCommands::InterpretService.new(project, current_user).
         execute(params[:description], issuable)
 
-    params[:description] = description
+    # Avoid a description already set on an issuable to be overwritten by a nil
+    params[:description] = description if params.has_key?(:description)
 
     params.merge!(command_params)
   end

app/services/issues/base_service.rb

 module Issues
   class BaseService < ::IssuableBaseService
+    attr_reader :merge_request_for_resolving_discussions
+
+    def initialize(*args)
+      super
+
+      @merge_request_for_resolving_discussions ||= params.delete(:merge_request_for_resolving_discussions)
+    end
+
     def hook_data(issue, action)
       issue_data = issue.to_hook_data(current_user)
       issue_url = Gitlab::UrlBuilder.build(issue)

app/services/issues/build_service.rb

+module Issues
+  class BuildService < Issues::BaseService
+    def execute
+      @issue = project.issues.new(issue_params)
+    end
+
+    def issue_params_with_info_from_merge_request
+      return {} unless merge_request_for_resolving_discussions
+
+      { title: title_from_merge_request, description: description_from_merge_request }
+    end
+
+    def title_from_merge_request
+      "Follow-up from \"#{merge_request_for_resolving_discussions.title}\""
+    end
+
+    def description_from_merge_request
+      if merge_request_for_resolving_discussions.resolvable_discussions.empty?
+        return "There are no unresolved discussions. "\
+               "Review the conversation in #{merge_request_for_resolving_discussions.to_reference}"
+      end
+
+      description = "The following discussions from #{merge_request_for_resolving_discussions.to_reference} should be addressed:"
+      [description, *items_for_discussions].join("\n\n")
+    end
+
+    def items_for_discussions
+      merge_request_for_resolving_discussions.resolvable_discussions.map { |discussion| item_for_discussion(discussion) }
+    end
+
+    def item_for_discussion(discussion)
+      first_note = discussion.first_note_to_resolve
+      other_note_count = discussion.notes.size - 1
+      creation_time = first_note.created_at.to_s(:medium)
+      note_url = Gitlab::UrlBuilder.build(first_note)
+
+      discussion_info = "- [ ] #{first_note.author.to_reference} commented in a discussion on [#{creation_time}](#{note_url}): "
+      discussion_info << " (+#{other_note_count} #{'comment'.pluralize(other_note_count)})" if other_note_count > 0
+
+      note_without_block_quotes = Banzai::Filter::BlockquoteFenceFilter.new(first_note.note).call
+      quote = ">>>\n#{note_without_block_quotes}\n>>>"
+
+      [discussion_info, quote].join("\n\n")
+    end
+
+    def issue_params
+      @issue_params ||= issue_params_with_info_from_merge_request.merge(params.slice(:title, :description))
+    end
+  end
+end

app/services/issues/create_service.rb

@@ -4,7 +4,8 @@ module Issues
       @request = params.delete(:request)
       @api = params.delete(:api)
 
-      @issue = project.issues.new
+      issue_attributes = params.merge(merge_request_for_resolving_discussions: merge_request_for_resolving_discussions)
+      @issue = BuildService.new(project, current_user, issue_attributes).execute
 
       create(@issue)
     end
@@ -18,6 +19,17 @@ module Issues
       notification_service.new_issue(issuable, current_user)
       todo_service.new_issue(issuable, current_user)
       user_agent_detail_service.create
+
+      if merge_request_for_resolving_discussions.try(:discussions_can_be_resolved_by?, current_user)
+        resolve_discussions_in_merge_request(issuable)
+      end
+    end
+
+    def resolve_discussions_in_merge_request(issue)
+      Discussions::ResolveService.new(project, current_user,
+                                      merge_request: merge_request_for_resolving_discussions,
+                                      follow_up_issue: issue).
+          execute(merge_request_for_resolving_discussions.resolvable_discussions)
     end
 
     private

app/services/system_note_service.rb

@@ -163,6 +163,14 @@ module SystemNoteService
     create_note(noteable: merge_request, project: project, author: author, note: body)
   end
 
+  def discussion_continued_in_issue(discussion, project, author, issue)
+    body = "Added #{issue.to_reference} to continue this discussion"
+    note_attributes = discussion.reply_attributes.merge(project: project, author: author, note: body)
+    note_attributes[:type] = note_attributes.delete(:note_type)
+
+    create_note(note_attributes)
+  end
+
   # Called when the title of a Noteable is changed
   #
   # noteable  - Noteable object that responds to `title`

app/views/projects/merge_requests/widget/open/_unresolved_discussions.html.haml

@@ -3,4 +3,8 @@
   This merge request has unresolved discussions
 
 %p
-  Please resolve these discussions to allow this merge request to be merged.
+  Please resolve these discussions
\ No newline at end of file
+  - if @project.issues_enabled? && can?(current_user, :create_issue, @project)
+    or
+    = link_to "open an issue to resolve them later", new_namespace_project_issue_path(@project.namespace, @project, merge_request_for_resolving_discussions: @merge_request.iid)
+  to allow this merge request to be merged.

app/views/shared/issuable/_form.html.haml

@@ -42,6 +42,21 @@
 
 = render 'shared/issuable/form/branch_chooser', issuable: issuable, form: form
 
+- if @merge_request_for_resolving_discussions
+  .form-group
+    .col-sm-10.col-sm-offset-2
+      - if @merge_request_for_resolving_discussions.discussions_can_be_resolved_by?(current_user)
+        = icon('exclamation-triangle')
+        Creating this issue will mark all discussions in
+        = link_to @merge_request_for_resolving_discussions.to_reference, merge_request_path(@merge_request_for_resolving_discussions)
+        as resolved.
+        = hidden_field_tag 'merge_request_for_resolving_discussions', @merge_request_for_resolving_discussions.iid
+      - else
+        = icon('exclamation-triangle')
+        You can't automatically mark all discussions in
+        = link_to @merge_request_for_resolving_discussions.to_reference, merge_request_path(@merge_request_for_resolving_discussions)
+        as resolved. Ask someone with sufficient rights to resolve the them.
+
 - is_footer = !(issuable.is_a?(MergeRequest) && issuable.new_record?)
 .row-content-block{class: (is_footer ? "footer-block" : "middle-block")}
   - if issuable.new_record?

changelogs/unreleased/23589-open-issue-for-mr.yml

+---
+title: Resolve all discussions in a merge request by creating an issue collecting
+  them
+merge_request: 7180
+author: Bob Van Landuyt

doc/api/issues.md

@@ -330,6 +330,7 @@ POST /projects/:id/issues
 | `labels`        | string  | no  | Comma-separated label names for an issue  |
 | `created_at`    | string  | no  | Date time string, ISO 8601 formatted, e.g. `2016-03-11T03:45:40Z` (requires admin or project owner rights) |
 | `due_date`      | string  | no  | Date time string in the format YEAR-MONTH-DAY, e.g. `2016-03-11` |
+| `merge_request_for_resolving_discussions` | integer | no       | The IID of a merge request in which to resolve all issues. This will fill the issue with a default description and mark all discussions as resolved. When passing a description or title, these values will take precedence over the default values. |
 
 ```bash
 curl --request POST --header "PRIVATE-TOKEN: 9koXpg98eAheJpvBs5tK" https://gitlab.example.com/api/v3/projects/4/issues?title=Issues%20with%20auth&labels=bug

doc/user/project/merge_requests/merge_request_discussion_resolution.md

@@ -37,7 +37,8 @@ resolved discussions tracker.
 
 > [Introduced][ce-7125] in GitLab 8.14.
 
-You can prevent merge requests from being merged until all discussions are resolved.
+You can prevent merge requests from being merged until all discussions are
+resolved.
 
 Navigate to your project's settings page, select the
 **Only allow merge requests to be merged if all discussions are resolved** check
@@ -50,8 +51,26 @@ are resolved.
 
 ![Only allow merge if all the discussions are resolved message](img/only_allow_merge_if_all_discussions_are_resolved_msg.png)
 
+### Move all unresolved discussions in a merge request to an issue
+
+> [Introduced][ce-7180] (Currently on Backlog)
+
+To delegate unresolved discussions to a new issue you can click the link **open
+an issue to resolve them later**.
+
+This will prepare an issue with content referring to the merge request and
+discussions.
+
+![Issue mentioning discussions in a merge request](img/preview_issue_for_discussions.png)
+
+Hitting **Submit issue** will cause all discussions to be marked as resolved and
+add a note referring to the newly created issue.
+
+You can now proceed to merge the merge request from the UI.
+
 [ce-5022]: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/5022
 [ce-7125]: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7125
+[ce-7180]: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/7180
 [resolve-discussion-button]: img/resolve_discussion_button.png
 [resolve-comment-button]: img/resolve_comment_button.png
 [discussion-view]: img/discussion_view.png

lib/api/issues.rb

@@ -28,6 +28,14 @@ module API
 
         new_params
       end
+
+      def merge_request_for_resolving_discussions
+        return unless merge_request_iid = params[:merge_request_for_resolving_discussions]
+
+        @merge_request_for_resolving_discussions ||= MergeRequestsFinder.new(current_user, project_id: user_project.id).
+                                                       execute.
+                                                       find_by(iid: merge_request_iid)
+      end
     end
 
     resource :issues do
@@ -160,15 +168,19 @@ module API
       #   created_at (optional)                              - Date time string, ISO 8601 formatted
       #   due_date (optional)                                - Date time string in the format YEAR-MONTH-DAY
       #   confidential (optional)                            - Boolean parameter if the issue should be confidential
+      #   merge_request_for_resolving_discussions (optional) - The IID of a merge request for which to resolve discussions
       # Example Request:
       #   POST /projects/:id/issues
       post ':id/issues' do
         required_attributes! [:title]
 
-        keys = [:title, :description, :assignee_id, :milestone_id, :due_date, :confidential, :labels]
+        keys = [:title, :description, :assignee_id, :milestone_id, :due_date, :confidential, :labels, :merge_request_for_resolving_discussions]
         keys << :created_at if current_user.admin? || user_project.owner == current_user
         attrs = attributes_for_keys(keys)
 
+        attrs[:labels] = params[:labels] if params[:labels]
+        attrs[:merge_request_for_resolving_discussions] = merge_request_for_resolving_discussions if params[:merge_request_for_resolving_discussions]
+
         # Convert and filter out invalid confidential flags
         attrs['confidential'] = to_boolean(attrs['confidential'])
         attrs.delete('confidential') if attrs['confidential'].nil?

spec/controllers/projects/issues_controller_spec.rb

@@ -55,6 +55,30 @@ describe Projects::IssuesController do
   end
 
   describe 'GET #new' do
+    context 'internal issue tracker' do
+      before do
+        sign_in(user)
+        project.team << [user, :developer]
+      end
+
+      it 'builds a new issue' do
+        get :new, namespace_id: project.namespace.path, project_id: project
+
+        expect(assigns(:issue)).to be_a_new(Issue)
+      end
+
+      it 'fills in an issue for a merge request' do
+        project_with_repository = create(:project)
+        project_with_repository.team << [user, :developer]
+        mr = create(:merge_request_with_diff_notes, source_project: project_with_repository)
+
+        get :new, namespace_id: project_with_repository.namespace.path, project_id: project_with_repository, merge_request_for_resolving_discussions: mr.iid
+
+        expect(assigns(:issue).title).not_to be_empty
+        expect(assigns(:issue).description).not_to be_empty
+      end
+    end
+
     context 'external issue tracker' do
       it 'redirects to the external issue tracker' do
         external = double(new_issue_path: 'https://example.com/issues/new')
@@ -272,6 +296,42 @@ describe Projects::IssuesController do
   end
 
   describe 'POST #create' do
+    context 'resolving discussions in MergeRequest' do
+      let(:discussion) { Discussion.for_diff_notes([create(:diff_note_on_merge_request)]).first }
+      let(:merge_request) { discussion.noteable }
+      let(:project) { merge_request.source_project }
+
+      before do
+        project.team << [user, :master]
+        sign_in user
+      end
+
+      let(:merge_request_params) do
+        { merge_request_for_resolving_discussions: merge_request.iid }
+      end
+
+      def post_issue(issue_params)
+        post :create, namespace_id: project.namespace.to_param, project_id: project.to_param, issue: issue_params, merge_request_for_resolving_discussions: merge_request.iid
+      end
+
+      it 'creates an issue for the project' do
+        expect { post_issue({ title: 'Hello' }) }.to change { project.issues.reload.size }.by(1)
+      end
+
+      it "doesn't overwrite given params" do
+        post_issue(description: 'Manually entered description')
+
+        expect(assigns(:issue).description).to eq('Manually entered description')
+      end
+
+      it 'resolves the discussion in the merge_request' do
+        post_issue(title: 'Hello')
+        discussion.first_note.reload
+
+        expect(discussion.resolved?).to eq(true)
+      end
+    end
+
     context 'Akismet is enabled' do
       before do
         allow_any_instance_of(SpamService).to receive(:check_for_spam?).and_return(true)

spec/features/issues/create_issue_for_discussions_in_merge_request_spec.rb

+require 'rails_helper'
+
+feature 'Resolving all open discussions in a merge request from an issue', feature: true do
+  let(:user) { create(:user) }
+  let(:project) { create(:project, only_allow_merge_if_all_discussions_are_resolved: true) }
+  let(:merge_request) { create(:merge_request, source_project: project) }
+  let!(:discussion) { Discussion.for_diff_notes([create(:diff_note_on_merge_request, noteable: merge_request, project: project)]).first }
+
+  before do
+    project.team << [user, :master]
+    login_as user
+  end
+
+  context 'with the internal tracker disabled' do
+    before do
+      project.project_feature.update_attribute(:issues_access_level, ProjectFeature::DISABLED)
+      visit namespace_project_merge_request_path(project.namespace, project, merge_request)
+    end
+
+    it 'does not show a link to create a new issue' do
+      expect(page).not_to have_link 'open an issue to resolve them later'
+    end
+  end
+
+  context 'merge request has discussions that need to be resolved' do
+    before do
+      visit namespace_project_merge_request_path(project.namespace, project, merge_request)
+    end
+
+    it 'shows a warning that the merge request contains unresolved discussions' do
+      expect(page).to have_content 'This merge request has unresolved discussions'
+    end
+
+    it 'has a link to resolve all discussions by creating an issue' do
+      page.within '.mr-widget-body' do
+        expect(page).to have_link 'open an issue to resolve them later', href: new_namespace_project_issue_path(project.namespace, project, merge_request_for_resolving_discussions: merge_request.iid)
+      end
+    end
+
+    context 'creating an issue for discussions' do
+      before do
+        page.click_link 'open an issue to resolve them later', href: new_namespace_project_issue_path(project.namespace, project, merge_request_for_resolving_discussions: merge_request.iid)
+      end
+
+      it 'shows an issue with the title filled in' do
+        title_field = page.find_field('issue[title]')
+
+        expect(title_field.value).to include(merge_request.title)
+      end
+
+      it 'has a mention of the discussion in the description'  do
+        description_field = page.find_field('issue[description]')
+
+        expect(description_field.value).to include(discussion.first_note.note)
+      end
+
+      it 'has a hidden field for the merge request' do
+        merge_request_field = find('#merge_request_for_resolving_discussions', visible: false)
+
+        expect(merge_request_field.value).to eq(merge_request.iid.to_s)
+      end
+
+      it 'can create a new issue for the project' do
+        expect { click_button 'Submit issue' }.to change { project.issues.reload.size }.by(1)
+      end
+
+      it 'resolves the discussion in the merge request' do
+        click_button 'Submit issue'
+
+        discussion.first_note.reload
+
+        expect(discussion.resolved?).to eq(true)
+      end
+    end
+  end
+end

spec/models/discussion_spec.rb

@@ -521,6 +521,15 @@ describe Discussion, model: true do
     end
   end
 
+  describe "#first_note_to_resolve" do
+    it "returns the first not that still needs to be resolved" do
+      allow(first_note).to receive(:to_be_resolved?).and_return(false)
+      allow(second_note).to receive(:to_be_resolved?).and_return(true)
+
+      expect(subject.first_note_to_resolve).to eq(second_note)
+    end
+  end
+
   describe "#collapsed?" do
     context "when a diff discussion" do
       before do

spec/models/merge_request_spec.rb

@@ -1124,6 +1124,46 @@ describe MergeRequest, models: true do
       allow(subject).to receive(:diff_discussions).and_return([first_discussion, second_discussion, third_discussion])
     end
 
+    describe '#resolvable_discussions' do
+      before do
+        allow(first_discussion).to receive(:to_be_resolved?).and_return(true)
+        allow(second_discussion).to receive(:to_be_resolved?).and_return(false)
+        allow(third_discussion).to receive(:to_be_resolved?).and_return(false)
+      end
+
+      it 'includes only discussions that need to be resolved' do
+        expect(subject.resolvable_discussions).to eq([first_discussion])
+      end
+    end
+
+    describe '#discussions_can_be_resolved_by? user' do
+      let(:user) { build(:user) }
+
+      context 'all discussions can be resolved by the user' do
+        before do
+          allow(first_discussion).to receive(:can_resolve?).with(user).and_return(true)
+          allow(second_discussion).to receive(:can_resolve?).with(user).and_return(true)
+          allow(third_discussion).to receive(:can_resolve?).with(user).and_return(true)
+        end
+
+        it 'allows a user to resolve the discussions' do
+          expect(subject.discussions_can_be_resolved_by?(user)).to be(true)
+        end
+      end
+
+      context 'one discussion cannot be resolved by the user' do
+        before do
+          allow(first_discussion).to receive(:can_resolve?).with(user).and_return(true)
+          allow(second_discussion).to receive(:can_resolve?).with(user).and_return(true)
+          allow(third_discussion).to receive(:can_resolve?).with(user).and_return(false)
+        end
+
+        it 'allows a user to resolve the discussions' do
+          expect(subject.discussions_can_be_resolved_by?(user)).to be(false)
+        end
+      end
+    end
+
     describe "#discussions_resolvable?" do
       context "when all discussions are unresolvable" do
         before do

spec/requests/api/issues_spec.rb

@@ -692,6 +692,32 @@ describe API::Issues, api: true  do
       ])
     end
 
+    context 'resolving issues in a merge request' do
+      let(:discussion) { Discussion.for_diff_notes([create(:diff_note_on_merge_request)]).first }
+      let(:merge_request) { discussion.noteable }
+      let(:project) { merge_request.source_project }
+      before do
+        project.team << [user, :master]
+        post api("/projects/#{project.id}/issues", user),
+             title: 'New Issue',
+             merge_request_for_resolving_discussions: merge_request.iid
+      end
+
+      it 'creates a new project issue' do
+        expect(response).to have_http_status(:created)
+      end
+
+      it 'resolves the discussions in a merge request' do
+        discussion.first_note.reload
+
+        expect(discussion.resolved?).to be(true)
+      end
+
+      it 'assigns a description to the issue mentioning the merge request' do
+        expect(json_response['description']).to include(merge_request.to_reference)
+      end
+    end
+
     context 'with due date' do
       it 'creates a new project issue' do
         due_date = 2.weeks.from_now.strftime('%Y-%m-%d')

spec/services/discussions/resolve_service_spec.rb

+require 'spec_helper'
+
+describe Discussions::ResolveService do
+  describe '#execute' do
+    let(:discussion) { Discussion.for_diff_notes([create(:diff_note_on_merge_request)]).first }
+    let(:project) { merge_request.project }
+    let(:merge_request) { discussion.noteable }
+    let(:user) { create(:user) }
+    let(:service) { described_class.new(discussion.noteable.project, user, merge_request: merge_request) }
+
+    before do
+      project.team << [user, :master]
+    end
+
+    it "doesn't resolve discussions the user can't resolve" do
+      expect(discussion).to receive(:can_resolve?).with(user).and_return(false)
+
+      service.execute(discussion)
+
+      expect(discussion.resolved?).to be(false)
+    end
+
+    it 'resolves the discussion' do
+      service.execute(discussion)
+
+      expect(discussion.resolved?).to be(true)
+    end
+
+    it 'executes the notification service' do
+      expect_any_instance_of(MergeRequests::ResolvedDiscussionNotificationService).to receive(:execute).with(discussion.noteable)
+
+      service.execute(discussion)
+    end
+
+    it 'adds a system note to the discussion' do
+      issue = create(:issue, project: project)
+
+      expect(SystemNoteService).to receive(:discussion_continued_in_issue).with(discussion, project, user, issue)
+      service = described_class.new(project, user, merge_request: merge_request, follow_up_issue: issue)
+      service.execute(discussion)
+    end
+
+    it 'can resolve multiple discussions at once' do
+      other_discussion = Discussion.for_diff_notes([create(:diff_note_on_merge_request, noteable: discussion.noteable, project: discussion.noteable.source_project)]).first
+
+      service.execute([discussion, other_discussion])
+
+      expect(discussion.resolved?).to be(true)
+      expect(other_discussion.resolved?).to be(true)
+    end
+  end
+end

spec/services/issues/build_service_spec.rb

+require 'spec_helper.rb'
+
+describe Issues::BuildService, services: true do
+  let(:project) { create(:project) }
+  let(:user) { create(:user) }
+
+  before do
+    project.team << [user, :developer]
+  end
+
+  context 'for discussions in a merge request' do
+    let(:merge_request) { create(:merge_request_with_diff_notes, source_project: project) }
+    let(:issue) { described_class.new(project, user, merge_request_for_resolving_discussions: merge_request).execute }
+
+    def position_on_line(line_number)
+      Gitlab::Diff::Position.new(
+        old_path: "files/ruby/popen.rb",
+        new_path: "files/ruby/popen.rb",
+        old_line: nil,
+        new_line: line_number,
+        diff_refs: merge_request.diff_refs
+      )
+    end
+
+    describe '#items_for_discussions' do
+      it 'has an item for each discussion' do
+        create(:diff_note_on_merge_request, noteable: merge_request, project: merge_request.source_project, position: position_on_line(13))
+        service = described_class.new(project, user, merge_request_for_resolving_discussions: merge_request)
+
+        service.execute
+
+        expect(service.items_for_discussions.size).to eq(2)
+      end
+    end
+
+    describe '#item_for_discussion' do
+      let(:service) { described_class.new(project, user, merge_request_for_resolving_discussions: merge_request) }
+
+      it 'mentions the author of the note' do
+        discussion = Discussion.new([create(:diff_note_on_merge_request, author: create(:user, username: 'author'))])
+        expect(service.item_for_discussion(discussion)).to include('@author')
+      end
+
+      it 'wraps the note in a blockquote' do
+        note_text = "This is a string\n"\
+                    ">>>\n"\
+                    "with a blockquote\n"\
+                    "> That has a quote\n"\
+                    ">>>\n"
+        note_result = "This is a string\n"\
+                    "> with a blockquote\n"\
+                    "> > That has a quote\n"
+        discussion = Discussion.new([create(:diff_note_on_merge_request, note: note_text)])
+        expect(service.item_for_discussion(discussion)).to include(">>>\n#{note_result}\n>>>")
+      end
+    end
+
+    describe '#execute' do
+      it 'has the merge request reference in the title' do
+        expect(issue.title).to include(merge_request.title)
+      end
+
+      it 'has the reference of the merge request in the description' do
+        expect(issue.description).to include(merge_request.to_reference)
+      end
+
+      it 'does not assign title when a title was given' do
+        issue = described_class.new(project, user,
+                                    merge_request_for_resolving_discussions: merge_request,
+                                    title: 'What an issue').execute
+
+        expect(issue.title).to eq('What an issue')
+      end
+
+      it 'does not assign description when a description was given' do
+        issue = described_class.new(project, user,
+                                    merge_request_for_resolving_discussions: merge_request,
+                                    description: 'Fix at your earliest conveignance').execute
+
+        expect(issue.description).to eq('Fix at your earliest conveignance')
+      end
+
+      describe 'with multiple discussions' do
+        before do
+          create(:diff_note_on_merge_request, noteable: merge_request, project: merge_request.target_project, position: position_on_line(15))
+        end
+
+        it 'mentions all the authors in the description' do
+          authors = merge_request.diff_discussions.map(&:author)
+
+          expect(issue.description).to include(*authors.map(&:to_reference))
+        end
+
+        it 'has a link for each unresolved discussion in the description' do
+          notes = merge_request.diff_discussions.map(&:first_note)
+          links = notes.map { |note| Gitlab::UrlBuilder.build(note) }
+
+          expect(issue.description).to include(*links)
+        end
+
+        it 'mentions additional notes' do
+          create_list(:diff_note_on_merge_request, 2, noteable: merge_request, project: merge_request.target_project, position: position_on_line(15))
+
+          expect(issue.description).to include('(+2 comments)')
+        end
+      end
+    end
+  end
+
+  context 'For a merge request without discussions' do
+    let(:merge_request) { create(:merge_request, source_project: project) }
+
+    describe '#execute' do
+      it 'mentions the merge request in the description' do
+        issue = described_class.new(project, user, merge_request_for_resolving_discussions: merge_request).execute
+
+        expect(issue.description).to include("Review the conversation in #{merge_request.to_reference}")
+      end
+    end
+  end
+
+  describe '#execute' do
+    it 'builds a new issues with given params' do
+      issue = described_class.new(project, user, title: 'Issue #1', description: 'Issue description').execute
+
+      expect(issue.title).to eq('Issue #1')
+      expect(issue.description).to eq('Issue description')
+    end
+  end
+end

spec/services/issues/create_service_spec.rb

@@ -136,5 +136,48 @@ describe Issues::CreateService, services: true do
     end
 
     it_behaves_like 'new issuable record that supports slash commands'
+
+    context 'for a merge request' do
+      let(:discussion) { Discussion.for_diff_notes([create(:diff_note_on_merge_request)]).first }
+      let(:merge_request) { discussion.noteable }
+      let(:project) { merge_request.source_project }
+      let(:opts) { { merge_request_for_resolving_discussions: merge_request } }
+
+      before do
+        project.team << [user, :master]
+      end
+
+      it 'resolves the discussion for the merge request' do
+        described_class.new(project, user, opts).execute
+        discussion.first_note.reload
+
+        expect(discussion.resolved?).to be(true)
+      end
+
+      it 'added a system note to the discussion' do
+        described_class.new(project, user, opts).execute
+
+        reloaded_discussion = MergeRequest.find(merge_request.id).discussions.first
+
+        expect(reloaded_discussion.last_note.system).to eq(true)
+      end
+
+      it 'assigns the title and description for the issue' do
+        issue = described_class.new(project, user, opts).execute
+
+        expect(issue.title).not_to be_nil
+        expect(issue.description).not_to be_nil
+      end
+
+      it 'can set nil explicityly to the title and description' do
+        issue = described_class.new(project, user,
+                                    merge_request_for_resolving_discussions: merge_request,
+                                    description: nil,
+                                    title: nil).execute
+
+        expect(issue.description).to be_nil
+        expect(issue.title).to be_nil
+      end
+    end
   end
 end

spec/services/system_note_service_spec.rb

@@ -712,4 +712,32 @@ describe SystemNoteService, services: true do
       end
     end
   end
+
+  describe '.discussion_continued_in_issue' do
+    let(:discussion) { Discussion.for_diff_notes([create(:diff_note_on_merge_request)]).first }
+    let(:merge_request) { discussion.noteable }
+    let(:project) { merge_request.source_project }
+    let(:issue) { create(:issue, project: project) }
+    let(:user) { create(:user) }
+
+    def reloaded_merge_request
+      MergeRequest.find(merge_request.id)
+    end
+
+    before do
+      project.team << [user, :developer]
+    end
+
+    it 'creates a new note in the discussion' do
+      # we need to completely rebuild the merge request object, or the `@discussions` on the merge request are not reloaded.
+      expect { SystemNoteService.discussion_continued_in_issue(discussion, project, user, issue) }.
+        to change { reloaded_merge_request.discussions.first.notes.size }.by(1)
+    end
+
+    it 'mentions the created issue in the system note' do
+      note = SystemNoteService.discussion_continued_in_issue(discussion, project, user, issue)
+
+      expect(note.note).to include(issue.to_reference)
+    end
+  end
 end