How to handle empty matrix about paths-filter

[dorny]

You can use if condition like this:

test:
  needs: changes
  if: ${{ needs.changes.outputs.services != '[]' && needs.changes.outputs.services != '' }}
  strategy:
    matrix:
      service: ${{ fromJson(needs.changes.outputs.services) }}

Job if condition is evaluated before job is actually started. I think it's evaluated only once and is not affected by matrix strategy although I'm not 100% sure about that.

Both job and steps outputs are just strings. That's why you have to use fromJson() to parse it into array.
Empty array will be serialized as [] so you can simply check it in the if condition.
Second part of the condition just checks if it's not an empty string - that would mean some failure during changes job execution.

[sshymko]

To account for empty array formatting differences ([], [ ], etc.), the condition can be updated like so:

test:
  needs: changes
  if: ${{ needs.changes.outputs.services != '' && toJson(fromJson(needs.changes.outputs.services)) != '[]' }}

[sam-hoffman]

This worked great! Thank you so much, and thanks for this great action :)