Task "script" blocks do not support array types for parameters

[ad22]

Expected Behavior

$params.arrayVar[*] is expanded when referenced in the script

Actual Behavior

Error from server (BadRequest): error when creating "my-task.yaml": admission webhook "validation.webhook.pipeline.tekton.dev" denied the request: validation failed: variable type invalid in "\echo \"$(params.arrayVar[*])\"\n" for step script: taskspec.steps.script

Steps to Reproduce the Problem

Task

apiVersion: tekton.dev/v1beta1
kind: Task
metadata:
  name: test
spec:
  params:
  - name: arrayVar
    description: my array
    type: array
  steps:
  - name: test
    image: alpine:latest
    script: |
      echo "$(params.arrayVar[*])"

TaskRun

apiVersion: tekton.dev/v1beta1
kind: TaskRun
metadata:
  name: run
spec:
  taskRef:
    name: test
  params:
    - name: arrayVar
      value:
        - "a"
        - "b"

[imjasonh]

/type feature

[ghost]

Thanks for the report! We do document this though it's a little bit buried: https://github.com/tektoncd/pipeline/blob/master/docs/tasks.md#substituting-array-parameters

You must reference parameters of type array in a completely isolated string within a larger string array.

The script field is just a string rather than an array, so the substitution doesn't work here. Will keep this issue open as a feature request to support it though.

[ad22]

The script field is just a string rather than an array, so the substitution doesn't work here. Will keep this issue open as a feature request to support it though.

@sbwsg That makes sense, I didn't immediately make the connection when going through that line. I will open a PR to call out the script field explicitly in the docs, if that's ok.

This will be good to have if it can be implemented safely. As a workaround for my current task, I've create a space separated string type, which is almost equivalent since I'd guess the array expansion would be into a space separated string anyway.

[ghost]

the array expansion would be into a space separated string anyway

Interestingly this is one of the reasons that we don't support array expansion in strings - different use-cases expect different joining strings. In some cases space-separated is good, in others comma-separated would be preferable.

If you do decide to pursue this then I'd recommend soliciting feedback in one of our Working Group meetings.

Also, paging @skaegi here as well who looked into implementing JSONPath for our variable interpolation, which might have built-in syntax for this or otherwise provide a longer-term solution to this problem?

[skaegi]

See #1463 -- sorry this is a pretty typical use-case and I'm really late on getting back to working on this after the beta.

[tekton-robot]

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Reopen the issue with /reopen.
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/close

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[tekton-robot]

Stale issues rot after 30d of inactivity.
Mark the issue as fresh with /remove-lifecycle rotten.
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/lifecycle rotten

Send feedback to tektoncd/plumbing.

[tekton-robot]

Issues go stale after 90d of inactivity.
Mark the issue as fresh with /remove-lifecycle stale.
Stale issues rot after an additional 30d of inactivity and eventually close.
If this issue is safe to close now please do so with /close.

/lifecycle stale

Send feedback to tektoncd/plumbing.

[tekton-robot]

@tekton-robot: Closing this issue.

In response to this:

Rotten issues close after 30d of inactivity.
Reopen the issue with /reopen.
Mark the issue as fresh with /remove-lifecycle rotten.

/close

Send feedback to tektoncd/plumbing.

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[vdemeester]

/remove-lifecycle rotten
/remove-lifecycle stale
/reopen

[tekton-robot]

@vdemeester: Reopened this issue.

In response to this:

/remove-lifecycle rotten
/remove-lifecycle stale
/reopen

Instructions for interacting with me using PR comments are available here. If you have questions or suggestions related to my behavior, please file an issue against the kubernetes/test-infra repository.

[bobcatfish]

As @sbwsg explained this was by design (#2374 (comment)) if we want to change this, maybe we can open a separate issue to explore it?

[joaosilva15]

I found a workaround for anyone that stumbles on this. You can pass the array in the args section and then use the args in the script. In the above case, it would look something like

apiVersion: tekton.dev/v1beta1
kind: Task
metadata:
  name: test
spec:
  params:
  - name: arrayVar
    description: my array
    type: array
  steps:
  - name: test
    image: alpine:latest
    args: ["$(params.arrayVar[*])"]
    script: |
      echo "$@"

As per tekton documentation

A step can specify a script field, which contains the body of a script. That script is invoked as if it were stored inside the container image, and any args are passed directly to it.

[YevheniiPokhvalii]

I found a workaround for anyone that stumbles on this. You can pass the array in the args section and then use the args in the script. In the above case, it would look something like

apiVersion: tekton.dev/v1beta1
kind: Task
metadata:
  name: test
spec:
  params:
  - name: arrayVar
    description: my array
    type: array
  steps:
  - name: test
    image: alpine:latest
    args: ["$(params.arrayVar[*])"]
    script: |
      echo "$@"

As per tekton documentation

A step can specify a script field, which contains the body of a script. That script is invoked as if it were stored inside the container image, and any args are passed directly to it.

Nice solution by may not be suitable in some cases.