No variable substitution when using matrix and array the length of 1

[zregvart]

Expected Behavior

Variable substitution occurs regardless of the length of the array parameter. Example:

tkn pipeline start -f pipeline.yaml --showlog    
PipelineRun started: matrix-vars-run-6jd5z
Waiting for logs to be available...
[produce : set-var] cat

[use-vars : use-vars] cat

Actual Behavior

The variable expression is printed when the array has a length of 1. Example:

$ tkn pipeline start -f pipeline.yaml --showlog    
PipelineRun started: matrix-vars-run-6jd5z
Waiting for logs to be available...
[produce : set-var] cat

[use-vars : use-vars] $(tasks.produce.results.vars[*])

Steps to Reproduce the Problem

1. Create a file pipeline.yaml with content:

pipeline.yaml

---
apiVersion: tekton.dev/v1
kind: Pipeline
metadata:
  name: matrix-vars
spec:
  tasks:
    - name: produce
      matrix:
        params:
          - name: var
            value:
              - cat
              # - dog
              # - squirrel
      taskSpec:
        params:
          - name: var
            type: string
        results:
          - name: vars
            type: string
        steps:
          - name: set-var
            image: alpine
            script:
              echo -n $(params.var) | tee $(results.vars.path)
    - name: use-vars
      params:
        - name: vars
          value:
            - $(tasks.produce.results.vars[*])
      taskSpec:
        params:
          - name: vars
            type: array
        steps:
          - name: use-vars
            image: alpine
            args: ["$(params.vars[*])"]
            script:
              echo $*
	

2. Run tkn pipeline start -f pipeline.yaml --showlog
3. Examine the output to see:

PipelineRun started: matrix-vars-run-dt42r
Waiting for logs to be available...
[produce : set-var] cat

[use-vars : use-vars] $(tasks.produce.results.vars[*])

5. Uncomment any values of the produce.matrix.params["var"].values, so the length of the vars result from the produce Task is influenced, and notice that the expression is not printed but values from the result

Additional Info

• Kubernetes version:

  Output of kubectl version:

Client Version: v1.25.3
Kustomize Version: v4.5.7
Server Version: v1.30.0

• Tekton Pipeline version:

  Output of tkn version or kubectl get pods -n tekton-pipelines -l app=tekton-pipelines-controller -o=jsonpath='{.items[0].metadata.labels.version}'

Client version: 0.37.0
Pipeline version: v0.62.0