Align GVK format accepted by --channel flag

[dsimansk]

Bug report

Create a subscription

Usage:
  kn subscription create NAME [options]

Examples:

  # Create a subscription 'sub0' from InMemoryChannel 'pipe0' to a subscriber ksvc 'receiver'
  kn subscription create sub0 --channel imcv1beta1:pipe0 --sink ksvc:receiver

  # Create a subscription 'sub1' from KafkaChannel 'k1' to ksvc 'mirror', reply to a broker 'nest' and DeadLetterSink to a ksvc 'bucket'
  kn subscription create sub1 --channel messaging.knative.dev:v1alpha1:KafkaChannel:k1 --sink mirror --sink-reply broker:nest --sink-dead-letter bucket


Options:
      --channel string            Specify the channel to subscribe to. For the default channel, just use the name (e.g. 'mychannel'). A mapped channel type like 'imc' can be used as a prefix (e.g. 'imc:mychannel'). Finally you can specify the full coordinates to the referenced
                                  channel with Group:Version:Kind:Name (e.g. 'messaging.knative.dev:v1alpha1:KafkaChannel:mychannel').
  -n, --namespace string          Specify the namespace to operate in.
  -s, --sink string               Addressable sink for events. You can specify a broker, channel, Knative service or URI. Examples: '--sink broker:nest' for a broker 'nest', '--sink channel:pipe' for a channel 'pipe', '--sink ksvc:mysvc:mynamespace' for a Knative service 'mysvc' in
                                  another namespace 'mynamespace', '--sink https://event.receiver.uri' for an HTTP URI, '--sink ksvc:receiver' or simply '--sink receiver' for a Knative service 'receiver' in the current namespace. '--sink special.eventing.dev/v1alpha1/channels:pipe'
                                  for GroupVersionResource of v1alpha1 'pipe'. If a prefix is not provided, it is considered as a Knative service in the current namespace.

We should consider refactoring --channel flag on kn subscription create to be aligned within the same GVK format as --sink. There's common implementation for parsing it already, but for some reason it isn't used in case of Subscriptions.

Expected behavior

The --channel flag accepts the same GVK format as --sink and other similar option flags.

/kind bug
/kind good-first-issue
/kind cleanup

[xiangpingjiang]

/assign

[xiangpingjiang]

@dsimansk
hello David,
the expected format is like --channel channel:pipe and --channel special.eventing.dev/v1alpha1/channels:pipe ?

[dsimansk]

@dsimansk hello David, the expected format is like --channel channel:pipe and --channel special.eventing.dev/v1alpha1/channels:pipe ?

Yes, the same as for --sink flag.

[rhuss]

@xiangpingjiang are you still working on the issue ? If not, no problem, but we would then assign it to somebody else who is also interested. Please let me know until tomorrow, otherwise, I would unassign you if this is ok

[xiangpingjiang]

@rhuss
No problem. I unassigned myself

[TheRealSibasishBehera]

/assign

[mabulgu]

@rhuss is this sth still unassigned (and undone)? If so I want to take a look at this.

[rhuss]

AFAIK it's still an open issue, hapyy to support you if you would like to give it a try!
@dsimansk can also help you here.

[mabulgu]

/assign