fix: nil-pointer-dereference when the item is deleted during single subscription (#220)

On-behalf-of: @SAP a.shcherbatiuk@sap.com

Signed-off-by: Artem Shcherbatiuk <vertex451@gmail.com>

Author: vertex451

gateway/resolver/subscription.go

@@ -186,7 +186,12 @@ func (r *Service) runWatch(
 					select {
 					case <-ctx.Done():
 						return
-					case resultChannel <- singleObj.Object:
+					case resultChannel <- func() interface{} {
+						if singleObj == nil { // object will be nil in case it is deleted
+							return nil
+						}
+						return singleObj.Object
+					}():
 					}
 				} else {
 					items := make([]unstructured.Unstructured, 0, len(previousObjects))

tests/gateway_test/subscription_test.go

@@ -26,12 +26,13 @@ func (suite *CommonTestSuite) TestSchemaSubscribe() {
 		expectError    bool
 	}{
 		{
-			testName:       "subscribe_deployment_and_create_deployment_OK",
+			testName:       "subscribe_create_and_delete_deployment_OK",
 			subscribeQuery: SubscribeDeployment("my-new-deployment", false),
 			setupFunc: func(ctx context.Context) {
 				suite.createDeployment(ctx, "my-new-deployment", map[string]string{"app": "my-app"})
+				suite.deleteDeployment(ctx, "my-new-deployment")
 			},
-			expectedEvents: 1,
+			expectedEvents: 2,
 		},
 		{
 			testName:       "subscribe_to_replicas_change_OK",