Support dry-run in the admission webhook

[afrittoli]

Expected Behavior

I can kubectl diff tekton pipeline resources

Actual Behavior

On the plumbing repo:

$ kubectl diff -f tekton/resources/prerelease_checks.yaml
Error from server (InternalError): Internal error occurred: admission webhook "webhook.tekton.dev" does not support dry run

[vdemeester]

/kind feature

[imjasonh]

Good news! This will be very easy to support once we (bad news!) upgrade to the latest knative/pkg and adopt their new style for expressing webhooks.

Basically it boils down to specifying in the ValidatingAdmissionController YAML that validations don't have side effects.

[vincent-pli]

@imjasonh
I think knative/pkg still not support this in it's latest webhook implements.

[imjasonh]

The way knative/serving uses knative/pkg, the config is in YAML instead of Go, so it's easier to configure it to support dry-run: https://github.com/knative/serving/blob/master/config/500-webhook-configuration.yaml

[vincent-pli]

@imjasonh
I see, you are right, they made a controller for admissionregistration, thanks.

[vincent-pli]

Could be close, fix by #1894

[afrittoli]

Could be close, fix by #1894

Nice! This ended up in 0.11.0-rc1 - so as soon and I get that deployed, I'll test this one and close if it works.

[tekton-robot]

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[tekton-robot]

@tekton-robot: Closing this issue.

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