[EP-tech] Workflow - test for document metadata in eprint workflow

Hi,
I was trying to do something like this in the eprint/default.xml workflow, where we're replacing one field with another - but still want to display the field where someone already has set it:
<stage name="files">
    <component type="Upload" show_help="always"/>
    <component type="Documents">
      <epc:if test="OLD_DOCUMENT_FIELD">
          <field ref="OLD_DOCUMENT_FIELD"/>
      </epc:if>
      ... (normal document fields) ...
    </component>
  </stage>

This doesn't work, as the dataobject for the workflow is the EPrint, and the epc:test considers 'OLD_DOCUMENT_FIELD' as an eprint field (which doesn't exist).

Is there a way to perform logic relating to document from within an eprint workflow?
I've tried various things (and trawled through the source code) but haven't found a solution yet.

If there isn't currently a wat to achieve this, is it something that other people have wanted to do previously, or migth find useful?

For my specific needs, creating a new EPScript method e.g. EPrints::Script::Compiled::run_have_any_documents_got_field_set that would be called with the field in question:
<epc:if test="have_any_documents_got_field_set('OLD_DOCUMENT_FIELD')> ... </epc:if>
but if there was a wider requirement to be able to to this, then possibly allowing a call to e.g. test="$doc.field" might be a more sustainable approach.

Cheers,
John

John Salter
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