Update merge status timeout to 0

- Also stop polling if we get a bad response from the server.

app/assets/javascripts/vue_merge_request_widget/components/states/ready_to_merge.vue

@@ -159,9 +159,12 @@ export default {
         });
     },
     initiateMergePolling() {
-      simplePoll((continuePolling, stopPolling) => {
+      simplePoll(
+        (continuePolling, stopPolling) => {
           this.handleMergePolling(continuePolling, stopPolling);
-      });
+        },
+        { timeout: 0 },
+      );
     },
     handleMergePolling(continuePolling, stopPolling) {
       this.service
@@ -192,6 +195,7 @@ export default {
         })
         .catch(() => {
           new Flash(__('Something went wrong while merging this merge request. Please try again.')); // eslint-disable-line
+          stopPolling();
         });
     },
     initiateRemoveSourceBranchPolling() {

changelogs/unreleased/56970-fix-mr-stuck-loading-on-error.yml

+---
+title: Disable timeout on merge request merging poll
+merge_request: 25988
+author:
+type: fixed

spec/javascripts/vue_mr_widget/components/states/mr_widget_ready_to_merge_spec.js

@@ -376,11 +376,29 @@ describe('ReadyToMerge', () => {
     });
 
     describe('initiateMergePolling', () => {
+      beforeEach(() => {
+        jasmine.clock().install();
+      });
+
+      afterEach(() => {
+        jasmine.clock().uninstall();
+      });
+
       it('should call simplePoll', () => {
         const simplePoll = spyOnDependency(ReadyToMerge, 'simplePoll');
         vm.initiateMergePolling();
 
-        expect(simplePoll).toHaveBeenCalled();
+        expect(simplePoll).toHaveBeenCalledWith(jasmine.any(Function), { timeout: 0 });
+      });
+
+      it('should call handleMergePolling', () => {
+        spyOn(vm, 'handleMergePolling');
+
+        vm.initiateMergePolling();
+
+        jasmine.clock().tick(2000);
+
+        expect(vm.handleMergePolling).toHaveBeenCalled();
       });
     });