Merge branch '4304-fix-successful-rebase' into 'master'

Fix successful rebase throwing flash error message

Closes #4304

See merge request gitlab-org/gitlab-ee!3727

changelogs/unreleased-ee/4304-fix-successful-rebase.yml

+---
+title: Fix successful rebase throwing flash error message
+merge_request: 3727
+author:
+type: fixed

ee/app/assets/javascripts/vue_merge_request_widget/components/states/mr_widget_rebase.vue

@@ -50,7 +50,15 @@
 
         this.service.rebase()
           .then(() => {
-            simplePoll((continuePolling, stopPolling) => {
+            simplePoll(this.checkRebaseStatus);
+          })
+          .catch((error) => {
+            this.rebasingError = error.merge_error;
+            this.isMakingRequest = false;
+            Flash('Something went wrong. Please try again.');
+          });
+      },
+      checkRebaseStatus(continuePolling, stopPolling) {
         this.service.poll()
           .then(res => res.json())
           .then((res) => {
@@ -59,7 +67,7 @@
             } else {
               this.isMakingRequest = false;
 
-                    if (res.merge_error.length) {
+              if (res.merge_error && res.merge_error.length) {
                 this.rebasingError = res.merge_error;
                 Flash('Something went wrong. Please try again.');
               }
@@ -73,13 +81,6 @@
             Flash('Something went wrong. Please try again.');
             stopPolling();
           });
-            });
-          })
-          .catch((error) => {
-            this.rebasingError = error.merge_error;
-            this.isMakingRequest = false;
-            Flash('Something went wrong. Please try again.');
-          });
       },
     },
   };

spec/javascripts/vue_mr_widget/components/mr_widget_rebase_spec.js

 import Vue from 'vue';
+import eventHub from '~/vue_merge_request_widget/event_hub';
 import component from 'ee/vue_merge_request_widget/components/states/mr_widget_rebase.vue';
 import mountComponent from '../../helpers/vue_mount_component_helper';
 
@@ -75,4 +76,42 @@ describe('Merge request widget rebase component', () => {
       expect(text).toContain('to allow this merge request to be merged.');
     });
   });
+
+  describe('methods', () => {
+    it('checkRebaseStatus', (done) => {
+      spyOn(eventHub, '$emit');
+      vm = mountComponent(Component, {
+        mr: {},
+        service: {
+          rebase() {
+            return Promise.resolve();
+          },
+          poll() {
+            return Promise.resolve({
+              json() {
+                return {
+                  rebase_in_progress: false,
+                  merge_error: null,
+                };
+              },
+            });
+          },
+        },
+      });
+
+      vm.rebase();
+
+      // Wait for the rebase request
+      vm.$nextTick()
+        // Wait for the polling request
+        .then(vm.$nextTick())
+        // Wait for the eventHub to be called
+        .then(vm.$nextTick())
+        .then(() => {
+          expect(eventHub.$emit).toHaveBeenCalledWith('MRWidgetUpdateRequested');
+        })
+        .then(done)
+        .catch(done.fail);
+    });
+  });
 });