Error: java.lang.IllegalStateException: Duplicate key topic-id-1.dita

If in a *.ditamap file a *.dita file that contains <keyword keyref="..."/> is referenced more than twice then dita-ot-2.4.1 fails with following error: Error: java.lang.IllegalStateException: Duplicate key topic-id-1.dita

Steps to reproduce:

1. Create following files:

map.ditamap:

<!DOCTYPE map PUBLIC "-//OASIS//DTD DITA Map//EN" "dtd/map.dtd">
<map title="Error: java.lang.IllegalStateException: Duplicate key topic-id-1.dita">
   <topicref href="topic.dita"/>
   <topicref href="topic.dita"/>
   <topicref href="topic.dita"/>
   <keydef keys="VAR">
      <topicmeta><keywords><keyword>value</keyword></keywords></topicmeta>
   </keydef>
</map>

topic.dita:

<!DOCTYPE concept PUBLIC "-//OASIS//DTD DITA Concept//EN" "dtd/concept.dtd">
<concept id="topic-id">
   <title>Topic</title>
   <shortdesc>Lorem ipsum</shortdesc>
   <conbody><p><keyword keyref="VAR"/></p></conbody>
</concept>

1. Run dita-ot: dita -f html5 -i map.ditamap

Results:

• Actual: no output is generated; processing fails with following error: Error: java.lang.IllegalStateException: Duplicate key topic-1.dita
• Expected: in out/ at least the files index.html and topic.html should be created (see #2363 if the files topic-1.html and topic-2.html should also be created)

[jelovirt]

The fix proposed by @raducoravu would work around the null pointer, but would not fix the underlying issue. The duplicates need to be detected earlier on.

[raducoravu]

The code in the adjustResourceRenames could be re-written to accept duplicates in the created map like:

        final Map<URI, URI> rewrites = 
        		tasks.stream().filter(t -> t.out != null).collect(toMap(
                        t -> t.in.uri,
                        t -> t.out.uri,
                        (v1, v2) -> {
                            return v1;
                        }
                ));