Flaky source lookup while debugging apps deployed on Wildfly

When debugging an application deployed on Wildfly, some sources can not be found even though a matching source jar exists in Maven Central.

• create an html5 app
• put a breakpoint on MemberService.listAllMembers()
• Debug As > Debug on Server (choose Wildfly 10)
• when the web page is displayed, the breakpoint is hit
• go down the stacktrace, source should be downloaded for each line
• reach io.undertow.server.handlers.PredicateHandler, no source can be found

The problem is caused by the class file being found in the wildfly-cli client jar. But it has no matching source jar containing the Predicate.java file. The same class exists in undertow-core.jar, which has a matching source jar. But the source lookup stopped once it found wildfly-cli.jar, regardless if an actual source could be found. It should keep looking until an actual source is found