Does not reject multiple `--image` parameters

[jchesterpivotal]

What version of Knative Client?

Paste output of 'kn version'

$ kn version
Version:      v0.10.0
Build Date:   2019-11-07 15:02:21
Git Revision: 22c65d6
Supported APIs:
- serving.knative.dev/v1alpha1 (knative-serving v0.10.0)

What version of Knative Serving running on your cluster?

0.10

Expected Behavior

When I type kn update service --image example.com/first --image example.com/second, I expect to be told that I cannot provide two images.

Actual Behavior

kn accepts the command line without error or warning. It applies the last-provided argument. In the example above this means that the updated service has example.com/second as its image.

Steps to Reproduce the Problem

1. Create a service.
2. Update the service, using two different --image parameters.
3. Observe that no error occurs.
4. Use describe to observe that second parameter is applied.

[rhuss]

Indeed, that's a bug. Thanks for reporting.

[itsmurugappan]

same issue with the all the flags. I could give like

1. --requests-cpu 50m --requestspu 60m
2. --port=8080 --port=8081

[itsmurugappan]

@rhuss I tried couple of other popular CLI's they dont seem to have a catch for this. For example , the below works, creates deployment with the first image

kubectl create deployment test --image=image1 --image=image2

[rhuss]

@itsmurugappan thanks for the investigations. I guess this is kind of a limitation of Cobra. I wonder though whether there is a workaround there for validating that only a single argument can be used. Will look into this later this week as I have to get more knowledge about Cobra and whether it is still suitable when tackling #496 which requires support for dynamically generated options.

[duglin]

I believe Cobra supports flags that can be specified multiple times, right? Like --env. If so, we could make --image one of those but then check in to code to make sure exactly one value was provided.

[dsimansk]

@rhuss the original issue with --image flag is addressed in #647. However, per @itsmurugappan's review and suggestion there other flags that should be treated as unique.
Should I create a new issue to collect the list at least the most obvious/important ones?

Probably it would be worth to contribute flag feature e.g. UniqueStringVar back to spf13/pflag library, wdyt?

[rhuss]

I think its a good idea to also check our other flags.

wrt/ to contributing back: In principle that would be the way to go, but it looks like that spf13/cobra (and probably also "flags") is totally dead as a project. We are waiting for a PR to be merged over 6 months now, without any feedback yet: spf13/cobra#899

So I don't think its worth the effort.