depends 010 (AB)

The pipeline

<p:declare-step xmlns:acme="http://acme" xmlns:err="http://www.w3.org/ns/xproc-error" xmlns:p="http://www.w3.org/ns/xproc" version="3.0">
   <p:output port="result"/>
   <p:declare-step type="acme:test">
      <p:output port="result"/>
      <p:identity>
         <p:with-input>
            <inner/>
         </p:with-input>
      </p:identity>
   </p:declare-step>
   <p:identity name="first">
      <p:with-input>
         <doc1/>
      </p:with-input>
   </p:identity>
   <acme:test p:depends="i-do-not-exist"/>
</p:declare-step>