Fix error in MR widget after /merge slash command

app/controllers/projects/merge_requests_controller.rb

@@ -369,10 +369,13 @@ class Projects::MergeRequestsController < Projects::ApplicationController
   end
 
   def merge_widget_refresh
-    if merge_request.in_progress_merge_commit_sha || merge_request.state == 'merged'
-      @status = :success
-    elsif merge_request.merge_when_build_succeeds
+    if merge_request.merge_when_build_succeeds
       @status = :merge_when_build_succeeds
+    else
+      # Only MRs that can be merged end in this action
+      # MR can be already picked up for merge / merged already or can be waiting for worker to be picked up
+      # in last case it does not have any special status. Possible error is handled inside widget js function
+      @status = :success
     end
 
     render 'merge'

changelogs/unreleased/28176_merge_widget_fix.yml

+---
+title: Fix error in MR widget after /merge slash command
+merge_request: 9259
+author:

spec/controllers/projects/merge_requests_controller_spec.rb

@@ -1143,15 +1143,15 @@ describe Projects::MergeRequestsController do
       end
     end
 
-    context 'when no special status for MR' do
+    context 'when MR does not have special state' do
       let(:merge_request) { create(:merge_request, source_project: project) }
 
       it 'returns an OK response' do
         expect(response).to have_http_status(:ok)
       end
 
-      it 'sets status to nil' do
-        expect(assigns(:status)).to be_nil
+      it 'sets status to success' do
+        expect(assigns(:status)).to eq(:success)
         expect(response).to render_template('merge')
       end
     end