Import multiple issue assignees from GitLab export

When importing from a GitLab archive, an admin can carry over the
assignations. Other users can not.

When a regular user is importing an issue with multiple assignees, the
assignee is replaced with the current user, meaning we would try to
insert current user as an assignee multiple times.

By filtering the array before storing it, the import becomes more
robust.

changelogs/unreleased/bvl-import-zip-multiple-assignees.yml

+---
+title: Fix importing multiple assignees from GitLab export
+merge_request: 17718
+author:
+type: fixed

lib/gitlab/import_export/relation_factory.rb

@@ -70,6 +70,7 @@ module Gitlab
 
         update_user_references
         update_project_references
+        remove_duplicate_assignees
 
         reset_tokens!
         remove_encrypted_attributes!
@@ -83,6 +84,14 @@ module Gitlab
         end
       end
 
+      def remove_duplicate_assignees
+        return unless @relation_hash['issue_assignees']
+
+        # When an assignee did not exist in the members mapper, the importer is
+        # assigned. We only need to assign each user once.
+        @relation_hash['issue_assignees'].uniq!(&:user_id)
+      end
+
       def setup_note
         set_note_author
         # attachment is deprecated and note uploads are handled by Markdown uploader

spec/lib/gitlab/import_export/project.json

@@ -43,7 +43,6 @@
     {
       "id": 40,
       "title": "Voluptatem",
-      "assignee_id": 1,
       "author_id": 22,
       "project_id": 5,
       "created_at": "2016-06-14T15:02:08.340Z",
@@ -61,7 +60,23 @@
       "issue_assignees": [
         {
           "user_id": 1,
-          "issue_id": 1
+          "issue_id": 40
+        },
+        {
+          "user_id": 15,
+          "issue_id": 40
+        },
+        {
+          "user_id": 16,
+          "issue_id": 40
+        },
+        {
+          "user_id": 16,
+          "issue_id": 40
+        },
+        {
+          "user_id": 6,
+          "issue_id": 40
         }
       ],
       "milestone": {
@@ -319,8 +334,7 @@
     },
     {
       "id": 39,
-      "title": "Delectus veniam ratione in eos culpa et natus molestiae earum aut.",
-      "assignee_id": 20,
+      "title": "Issue without assignees",
       "author_id": 22,
       "project_id": 5,
       "created_at": "2016-06-14T15:02:08.233Z",
@@ -334,6 +348,7 @@
       "confidential": false,
       "due_date": null,
       "moved_to_id": null,
+      "issue_assignees": [],
       "milestone": {
         "id": 1,
         "title": "test milestone",
@@ -539,7 +554,6 @@
     {
       "id": 38,
       "title": "Quasi adipisci non cupiditate dolorem quo qui earum sed.",
-      "assignee_id": 1,
       "author_id": 6,
       "project_id": 5,
       "created_at": "2016-06-14T15:02:08.154Z",
@@ -756,7 +770,6 @@
     {
       "id": 37,
       "title": "Cupiditate quo aut ducimus minima molestiae vero numquam possimus.",
-      "assignee_id": 15,
       "author_id": 20,
       "project_id": 5,
       "created_at": "2016-06-14T15:02:08.051Z",
@@ -952,7 +965,6 @@
     {
       "id": 36,
       "title": "Necessitatibus dolor est enim quia rem suscipit quidem voluptas ullam.",
-      "assignee_id": 20,
       "author_id": 16,
       "project_id": 5,
       "created_at": "2016-06-14T15:02:07.958Z",
@@ -1148,7 +1160,6 @@
     {
       "id": 35,
       "title": "Repellat praesentium deserunt maxime incidunt harum porro qui.",
-      "assignee_id": 6,
       "author_id": 20,
       "project_id": 5,
       "created_at": "2016-06-14T15:02:07.832Z",
@@ -1344,7 +1355,6 @@
     {
       "id": 34,
       "title": "Ullam expedita deserunt libero consequatur quia dolor harum perferendis facere quidem.",
-      "assignee_id": 20,
       "author_id": 1,
       "project_id": 5,
       "created_at": "2016-06-14T15:02:07.717Z",
@@ -1540,7 +1550,6 @@
     {
       "id": 33,
       "title": "Numquam accusamus eos iste exercitationem magni non inventore.",
-      "assignee_id": 15,
       "author_id": 26,
       "project_id": 5,
       "created_at": "2016-06-14T15:02:07.611Z",
@@ -1736,7 +1745,6 @@
     {
       "id": 32,
       "title": "Necessitatibus magnam qui at velit consequatur perspiciatis.",
-      "assignee_id": 22,
       "author_id": 15,
       "project_id": 5,
       "created_at": "2016-06-14T15:02:07.431Z",
@@ -1932,7 +1940,6 @@
     {
       "id": 31,
       "title": "Libero nam magnam incidunt eaque placeat error et.",
-      "assignee_id": 1,
       "author_id": 16,
       "project_id": 5,
       "created_at": "2016-06-14T15:02:07.280Z",

spec/lib/gitlab/import_export/project_tree_restorer_spec.rb

@@ -4,7 +4,12 @@ include ImportExport::CommonUtil
 describe Gitlab::ImportExport::ProjectTreeRestorer do
   describe 'restore project tree' do
     before(:context) do
-      @user = create(:user)
+      # Using an admin for import, so we can check assignment of existing members
+      @user = create(:admin)
+      @existing_members = [
+        create(:user, username: 'bernard_willms'),
+        create(:user, username: 'saul_will')
+      ]
 
       RSpec::Mocks.with_temporary_scope do
         @project = create(:project, :builds_disabled, :issues_disabled, name: 'project', path: 'project')
@@ -63,8 +68,9 @@ describe Gitlab::ImportExport::ProjectTreeRestorer do
         expect(issue.reload.updated_at.to_s).to eq('2016-06-14 15:02:47 UTC')
       end
 
-      it 'has issue assignees' do
-        expect(Issue.where(title: 'Voluptatem').first.issue_assignees).not_to be_empty
+      it 'has multiple issue assignees' do
+        expect(Issue.find_by(title: 'Voluptatem').assignees).to contain_exactly(@user, *@existing_members)
+        expect(Issue.find_by(title: 'Issue without assignees').assignees).to be_empty
       end
 
       it 'contains the merge access levels on a protected branch' do