Cult of Foxx

Set a Computed Default and Manual Input Override

2 min read

Sometimes we want a default value for a Workflow to be computed, such as a date, but also the ability to adjust it as needed. Let’s explore an example of how to do this:

---
name: Computed Default and Manual Override
 
on:
  workflow_dispatch:
    inputs:
      date:
        description: 'Date Override MMDDYYYY'
        required: false
        default: ''
        type: string
 
jobs:
  get-date:
    if: ${{ !inputs.date }}
    runs-on: ubuntu-latest
    name: Get date
    outputs:
      date: ${{ steps.get-date.outputs.DATE }}
 
    steps:
      - name: Get the date
        id: 'get-date'
        run: echo "DATE=$(date +'%m%d%Y')" >> $GITHUB_OUTPUT
 
  build-image:
    if: always() && !contains(needs.*.result, 'failure')
    needs: get-date
    name: Build an image
    runs-on: ubuntu-latest
 
    steps:
      - name: Init Packer
        id: init
        run: "packer init ."
        shell: bash
        env:
          PACKER_GITHUB_API_TOKEN: ${{ secrets.PACKER_GITHUB_API_TOKEN }}
 
      - name: Run Packer
        id: run
        run: "packer build -only\"image-profile.provider.image\" ."
        env:
          IMAGE_NAME: "profile-${{ inputs.date || needs.get-date.outputs.date }}.img"
          PACKER_GITHUB_API_TOKEN: ${{ secrets.PACKER_GITHUB_API_TOKEN }}

If a date is supplied to inputs then the get-date job will not need to exist. Since it’s listed as a need, that will make that fail for this job so we use always() to get around that. However, we ALSO want it to fail if that job DOES exist because no override was supplied and something goes wrong (or if any other needs are included and fail!) so we add the !contains(needs.*.result, 'failure') which translates to “none of the needs have failed.”

This way you can easily have additional needs yet still use ones that may not exist depending on their execution which also allows you to override them.

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