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.

3 files changed, 71 insertions, 1 deletions

diff --git a/app/services/issues/base_service.rb b/app/services/issues/base_service.rb
index 9ea3ce084ba..742e834df97 100644
--- a/app/services/issues/base_service.rb
+++ b/app/services/issues/base_service.rb
@@ -1,5 +1,13 @@
 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)
diff --git a/app/services/issues/build_service.rb b/app/services/issues/build_service.rb
new file mode 100644
index 00000000000..a63982f60c8
--- /dev/null
+++ b/app/services/issues/build_service.rb
@@ -0,0 +1,50 @@
+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
diff --git a/app/services/issues/create_service.rb b/app/services/issues/create_service.rb
index ea1690f3e38..d2eb46ac41b 100644
--- a/app/services/issues/create_service.rb
+++ b/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