Trigger on pipeline and with path filter

I would like to trigger a pipeline when a stage in another pipeline has completed, but I only want to do it if there have been changes in a specific folder.

Triggering based on the source pipeline works as expected, but I don't see an option for setting path filters. If I add a normal trigger on path, it gets executed immediately if there are changes in the folder, and not when the source pipeline has completed:

trigger:
  paths:
    include:
    - path/to/folder/*

resources:
  pipelines:
  - pipeline: SourcePipeline
    source: SourcePipeline
    trigger:
      stages:
        - sourcestage

Is this possible to achieve in ADO? I guess an alternative is to still trigger it, but make a step or condition in the pipeline that aborts if no changes to files in the folder.

Path filters are not supported in the pipeline resource.

If you are able to detect if the folder changes in the source build, consider adding a build tag when that happens - for example, HAS_CHANGES:

- task: Bash@3
    inputs:
    targetType: 'inline'
    script: |
      echo "##vso[build.addbuildtag]$HAS_CHANGES"
    displayName: 'Set build tag: HAS_CHANGES'

You can then configure the pipeline resource in the destination pipeline as follows:

resources:
  pipelines:
  - pipeline: SourcePipeline
    source: SourcePipeline
    trigger:
      tags: # List of tags that when matched will trigger the pipeline. 
        - HAS_CHANGES
      stages: # List of stages that when complete will trigger the pipeline. 
        - sourcestage