backstage: Software Template Array Inputs Not Working As Expected

Expected Behavior

Current Behavior

Consider the following software template:

apiVersion: backstage.io/v1beta2
kind: Template
metadata:
  name: add-addon
  title: Addon
  description: Add addon
spec:
  owner: users
  type: website

  parameters:
    - title: Values
      properties:
       should-be-list:
          title: This is a title and is huge
          description: "this is a description you can't see"
          type: array
          items:
            type: string
  steps:
    - id: fetch-repo
      name: Fetch repo
      action: fetch:plain
      input:
        url: 'https://github.com/asummers/backstage/tree/master'

    - id: fetch-template
      name: Fetch Template
      action: fetch:template
      input:
        url: ./template2
        values:
          list: '{{parameters.should-be-list}}'

    - id: publish
      name: Publish
      action: publish:github:pull-request
      input:
        repoUrl: 'github.com?owner=asummers&repo=backstage'
        title: 'feat: Add addon'
        branchName: 'add-addon'
        description: |
          Add addon

  output:
    links:
      - url: '{{steps.publish.output.remoteUrl}}'
        text: 'Go to PR'

The resulting summary appears as expected with two separate elements and not a combined value

But if we consider the template file

[
{% set comma = joiner() %}
{% for value in values.list -%}
${{ comma() }}${{ value }}
{%- endfor %}
]

[
{% for value in values.list -%}
${{ value }},
{%- endfor %}
]

we get

[

a,.,b,.,c,.,d,:,1,2,3,4,,,w,.,x,.,y,.,z,:,9,8,7,6
]

[
a,.,b,.,c,.,d,:,1,2,3,4,,,w,.,x,.,y,.,z,:,9,8,7,6,
]

This means that the array is being converted to a string somewhere under the hood, which results in arrays disappearing.

Possible Solution

Fix CSS for form and pass along array as is.

Steps to Reproduce

See ## Current Behavior

Context

This makes array forms in software templates impossible as nunjucks does not provide split functionality, to correct the comma joining happening prematurely.

Your Environment

• NodeJS Version (v12): 14
• Operating System and Version (e.g. Ubuntu 14.04): Ubuntu 18.04
• Browser Information: Chrome