Reproduce issue with namespace default channel (v1beta1)

ns_default_channel_issue.bash

# 0. setup eventing at v0.18.4 and kafka
# 1. Set clusterwide channel to IMC (v1beta1) and namespace (knativetutorial) to Kafka (v1alpha1)
cat <<EOF | kubectl apply -f -
apiVersion: v1
kind: ConfigMap
metadata:
  name: default-ch-webhook
  namespace: knative-eventing
data:
  default-ch-config: |
    clusterDefault:
      apiVersion: messaging.knative.dev/v1beta1
      kind: InMemoryChannel
    namespaceDefault:
      knativetutorial:
        apiVersion: messaging.knative.dev/v1alpha1
        kind: KafkaChannel
        spec:
          numPartitions: 2
          replicationFactor: 1
EOF

# create a channel in default namespace

cat <<EOF | kubectl apply -f -
apiVersion: messaging.knative.dev/v1beta1
kind: Channel
metadata:
  name: my-channel
  namespace: default
EOF


# create a channel in knativetutorial namespace
cat <<EOF | kubectl apply -f -
apiVersion: messaging.knative.dev/v1beta1
kind: Channel
metadata:
  name: my-channel
  namespace: knativetutorial
EOF

# verify using kn
kn channel list -A

NAMESPACE         NAME         TYPE              URL                                                              AGE     READY   REASON
default           my-channel   InMemoryChannel   http://my-channel-kn-channel.default.svc.cluster.local           9m38s   True    
knativetutorial   my-channel   InMemoryChannel   http://my-channel-kn-channel.knativetutorial.svc.cluster.local   8m48s   True    

# notice that the channel in knativetutorial should be a kafka channel based on the CM set above