[API] Fix creating issue when assignee_id is empty42025-fix-issue-api

see https://gitlab.com/gitlab-org/gitlab-ce/issues/42025

3 files changed, 18 insertions, 2 deletions

diff --git a/changelogs/unreleased/42025-fix-issue-api.yml b/changelogs/unreleased/42025-fix-issue-api.yml
new file mode 100644
index 00000000000..abb83bb2fad
--- /dev/null
+++ b/changelogs/unreleased/42025-fix-issue-api.yml
@@ -0,0 +1,5 @@
+---
+title: "[API] Fix creating issue when assignee_id is empty"
+merge_request:
+author:
+type: fixed
diff --git a/lib/api/helpers/common_helpers.rb b/lib/api/helpers/common_helpers.rb
index 322624c6092..9993caa5249 100644
--- a/lib/api/helpers/common_helpers.rb
+++ b/lib/api/helpers/common_helpers.rb
@@ -3,8 +3,10 @@ module API
     module CommonHelpers
       def convert_parameters_from_legacy_format(params)
         params.tap do |params|
-          if params[:assignee_id].present?
-            params[:assignee_ids] = [params.delete(:assignee_id)]
+          assignee_id = params.delete(:assignee_id)
+
+          if assignee_id.present?
+            params[:assignee_ids] = [assignee_id]
           end
         end
       end
diff --git a/spec/requests/api/issues_spec.rb b/spec/requests/api/issues_spec.rb
index 320217f2032..43218755f4f 100644
--- a/spec/requests/api/issues_spec.rb
+++ b/spec/requests/api/issues_spec.rb
@@ -847,6 +847,15 @@ describe API::Issues, :mailer do
         expect(json_response['assignee']['name']).to eq(user2.name)
         expect(json_response['assignees'].first['name']).to eq(user2.name)
       end
+
+      it 'creates a new project issue when assignee_id is empty' do
+        post api("/projects/#{project.id}/issues", user),
+          title: 'new issue', assignee_id: ''
+
+        expect(response).to have_gitlab_http_status(201)
+        expect(json_response['title']).to eq('new issue')
+        expect(json_response['assignee']).to be_nil
+      end
     end
 
     context 'single assignee restrictions' do