pipelineception-007

The pipeline

<p:declare-step xmlns:err="http://www.w3.org/ns/xproc-error" xmlns:ex="http://example.com/ns" xmlns:p="http://www.w3.org/ns/xproc" xmlns:xs="http://www.w3.org/2001/XMLSchema" exclude-inline-prefixes="#all" name="main" version="3.0">
   <p:output port="result" sequence="true"/>
   <p:declare-step type="ex:test-pipeline">
      <p:output port="result" content-types="xml"/>
      <p:option name="opt" as="xs:string?"/>
      <p:choose>
         <p:when test="empty($opt)">
            <p:identity>
               <p:with-input>
                  <test-output/>
               </p:with-input>
            </p:identity>
         </p:when>
         <p:otherwise>
            <p:identity>
               <p:with-input>
                  <test-output opt="{$opt}"/>
               </p:with-input>
            </p:identity>
         </p:otherwise>
      </p:choose>
   </p:declare-step>
   <p:identity>
      <p:with-input>
         <wrapper>{ex:test-pipeline(map{'opt':'has-value', 'other': 'error'})?result}</wrapper>
      </p:with-input>
   </p:identity>
</p:declare-step>