Log the syncing source when WaitForSync fails

A controller may watch several sources. This change makes it easier
to debug which source fails to be synced.

Author: haiyanmeng

pkg/internal/controller/controller.go

@@ -197,7 +197,7 @@ func (c *Controller[request]) Start(ctx context.Context) error {
 					}
 					didStartSyncingSource.Store(true)
 					if err := syncingSource.WaitForSync(sourceStartCtx); err != nil {
-						err := fmt.Errorf("failed to wait for %s caches to sync: %w", c.Name, err)
+						err := fmt.Errorf("failed to wait for %s caches to sync %v: %w", c.Name, syncingSource, err)
 						log.Error(err, "Could not wait for Cache to sync")
 						sourceStartErrChan <- err
 					}

pkg/internal/controller/controller_test.go

@@ -171,7 +171,7 @@ var _ = Describe("controller", func() {
 
 			err = ctrl.Start(context.TODO())
 			Expect(err).To(HaveOccurred())
-			Expect(err.Error()).To(ContainSubstring("failed to wait for testcontroller caches to sync: timed out waiting for cache to be synced"))
+			Expect(err.Error()).To(ContainSubstring("failed to wait for testcontroller caches to sync kind source: *v1.Deployment: timed out waiting for cache to be synced"))
 		})
 
 		It("should not error when controller Start context is cancelled during Sources WaitForSync", func() {