Tekton Task result passed as empty to a downstream task

Question

I am creating a deployment pipeline that would deploy packages as either Python packages to Pypi or Docker containers. I want to ensure correct deployment Task is called by processing contents of a workspace and passing the verdict (either "Python" or "Docker") to a when block in downstream tasks.

The problem is that when I pass the result to a when block it does not match the values even though I believe it should, as when I log the result in the task that creates it, or even assign it to a parameter and log it in downstream tasks it has the expected contents.

Pipeline without the when block executes no problem.

System information:

$ tkn version
Client version: 0.15.0
Pipeline version: v0.24.1
Triggers version: v0.8.1

$ k version --short
Client Version: v1.19.0
Server Version: v1.19.0+b00ba52

Relevant tasks in pipeline:

- name: check-appropriate-build-task
  taskRef:
    kind: Task
    name: check-build-type
  workspaces:
    - name: source
      workspace: shared-workspace
  runAfter:
    - fetch-repository

- name: build-and-upload-python-package
  params:
    - name: TWINE_REPOSITORY_URL
      value: $(params.twine-url)
  when:
    - input: $(tasks.check-appropriate-build-task.results.build-type)
      operator: in
      values: 
        - "Python"
  taskRef:
    kind: Task
    name: upload-pypi
  workspaces:
    - name: source
      workspace: shared-workspace
  runAfter:
    - check-appropriate-build-task

check-build-type task:

apiVersion: tekton.dev/v1beta1
kind: Task
metadata:
  name: check-build-type
spec:
  results:
    - name: build-type
  workspaces:
    - name: source
  steps:
    - name: check-build-type
      image: alpine
      script: |
        if test -f "$(workspaces.source.path)/setup.cfg"; then
          if grep -q Python "$(workspaces.source.path)/setup.cfg"; then
              echo "Python" > $(results.build-type.path)
          fi
        elif test -f "$(workspaces.source.path)/Dockerfile"; then
            echo "Docker" > $(results.build-type.path)
        fi
        cat $(results.build-type.path)

Thanks in advance.

Answer 1

It appears that check is failing due to a trailing \n.

We can fix the check-build-type Task, replacing echo with echo -n.