Cross-refs to JDK 11 broken in Scaladoc 2.13

[ashawley]

While working on #383, I noticed that links to Javadoc don't work for JDK 11 and later with Scala 2.13. The warnings in the sbt console bear this out.

[warn] shared/src/main/scala/scala/xml/package.scala:11:1: Could not
[warn] find any member to link for "javax.xml.parsers.SAXParser".
[warn] /**
[warn] ^
[warn] shared/src/main/scala/scala/xml/parsing/FactoryAdapter.scala:188:3:
[warn] Could not find any member to link for "org.xml.sax.SAXException".
[warn]   /**
[warn]   ^
[warn] shared/src/main/scala/scala/xml/include/XIncludeException.scala:13:1:
[warn] Could not find any member to link for
[warn] "java.lang.Throwable#getMessage".
[warn] /**
[warn] ^
[warn] shared/src/main/scala/scala/xml/include/sax/EncodingHeuristics.scala:38:3:
[warn] Could not find any member to link for "java.io.IOException".
[warn]   /**
[warn]   ^

[ashawley]

This used to work when the code for apiMappings was added in #180. That was the days of JDK9 and Scala 2.13.0-M3. It seems it worked all the way to Scala 2.13.0-M5 but then broke with Scala-2.13.0-RC1.

[SethTisue]

I can't remember if this question has come up before: could this be outsourced to https://github.com/ThoughtWorksInc/sbt-api-mappings ?

[ashawley]

It is possible. This was a lighterweight solution, but there is also a particular configuration scala-xml has that sbt-api-mappings is missing about the java.xml module.

[ashawley]

Bug report filed upstream scala/bug#11839