Accessing parent value from triggered child pipeline

I’m seeing some oddness when trying to use the ?: operator for a pipeline triggered with another
pipeline. In the ‘child’ pipeline, the following works:

  • ${ trigger['tag'] }
  • ${ trigger['parentExecution']['trigger']['tag'] }

The following does not work:

  • ${ trigger['tag'] ?: trigger['parentExecution']['trigger']['tag'] }.

I’m trying to have a field show the tag version selected. This pipeline can be triggered manually or from another pipeline, I’d like to ensure we use the correct value.

The other odd note, is that i use something like this (${ trigger['tag'] ?: trigger['properties']['RELEASE_IMAGE'] } in another ‘parent’ pipeline and it works without a problem.

Maybe i’m not doing something correct. Suggestions?