kn trigger update doesn't remove filter

[dsimansk]

Bug report

Filter isn't removed with --filter type- flag as documentation states.

root@ocp-dynamic-7202 eventing]# kn trigger create mytrigger --broker default --sink svc:event-display --filter type=knative.dev.event
Trigger 'mytrigger' successfully created in namespace 'foobar'.
[root@ocp-dynamic-7202 eventing]# kn trigger describe mytrigger
Name:         mytrigger
Namespace:    foobar
Labels:       eventing.knative.dev/broker=default
Annotations:  eventing.knative.dev/creator=kube:admin, eventing.knative.dev/lastModifier=kube:admin
Age:          11s
Broker:       default
Filter:
  type:       knative.dev.event
Sink:
  Name:       event-display
  Namespace:  foobar
  Resource:   Service (serving.knative.dev/v1alpha1)
Conditions:
  OK TYPE                  AGE REASON
  ++ Ready                 10s
  ++ BrokerReady           11s
  ++ DependencyReady       11s
  ++ Subscribed            10s
  ++ SubscriberResolved    11s
[root@ocp-dynamic-7202 eventing]# kn trigger update mytrigger --filter type-
Trigger 'mytrigger' updated in namespace 'foobar'.
[root@ocp-dynamic-7202 eventing]# kn trigger describe mytrigger
Name:         mytrigger
Namespace:    foobar
Labels:       eventing.knative.dev/broker=default
Annotations:  eventing.knative.dev/creator=kube:admin, eventing.knative.dev/lastModifier=kube:admin
Age:          26s
Broker:       default
Filter:
  type:       knative.dev.event
Sink:
  Name:       event-display
  Namespace:  foobar
  Resource:   Service (serving.knative.dev/v1alpha1)
Conditions:
  OK TYPE                  AGE REASON
  ++ Ready                 25s
  ++ BrokerReady           26s
  ++ DependencyReady       26s
  ++ Subscribed            25s
  ++ SubscriberResolved    26s

Expected behavior

Filter is removed upon update.

Steps to reproduce the problem

1. kn trigger create mytrigger --broker default --sink svc:event-display --filter type=knative.dev.event
2. kn trigger update mytrigger --filter type-
3. kn trigger describe mytrigger

kn version

HEAD

Knative (serving/eventing) version

0.13.1

/kind good-first-issue

[dsimansk]

The root cause is located in TriggerBuilder.Filter function. The current impl works with merged map of filters, but it's never actually replaced only modified. Therefore keys to be removed are stuck there.

client/pkg/eventing/v1alpha1/client.go

Lines 188 to 192 in a858a25

	attributes := filter.Attributes
	if attributes == nil {
	attributes = &v1alpha1.TriggerFilterAttributes{}
	filter.Attributes = attributes
	}

The fix requires PR #745 to land first, because it handles a case of updating to empty filters state.

/assign dsimansk