Allow variable substitution in pipeline.tasks[].onError

[dmitry-mightydevops]

Feature request

This doc says that only CRD Task accept variable substitution for spec.steps[].onError

It woulod be nice to support same behavior in pipeline.tasks[].onError

Use case

pipeline: 
tasks:
  - name: test
    onError: $(params.deploy_if_tests_failed)

So for example I want a flexible control if I need to continue (or stop) the pipeline if tests failed passed via params.

For now It fails with the error:

Resource: "tekton.dev/v1, Resource=pipelines", GroupVersionKind: "tekton.dev/v1, Kind=Pipeline"
Name: "backend-build-pipeline", Namespace: "ci"
for: "STDIN": error when patching "STDIN": admission webhook "validation.webhook.pipeline.tekton.dev" denied the request: validation failed: invalid value: $(params.deploy.deploy_if_tests_failed): spec.tasks[10].OnError
PipelineTask OnError must be either "continue" or "stopAndFail"

[l-qing]

I also think this demand is reasonable.
Since steps can be set, should tasks also be supported without any side effects? @vdemeester

[vdemeester]

Hum, I do think this demand is reasonable indeed. I don't see why not implementing it, and I don't think it would have any bad side effect.

[afrittoli]

@dmitry-mightydevops and @l-qing - would either of you be interested in contributing the implementation for this?

[l-qing]

@dmitry-mightydevops and @l-qing - would either of you be interested in contributing the implementation for this?

I'll give it a try this weekend.

/assign