WatchEvent.context() may be null

[raboof]

While watching I sometimes see:

[error] Error occurred obtaining files to watch.  Terminating continuous execution...
[error] java.lang.NullPointerException
[error] 	at sun.nio.fs.UnixPath.toUnixPath(UnixPath.java:198)
[error] 	at sun.nio.fs.UnixPath.resolve(UnixPath.java:397)
[error] 	at sun.nio.fs.UnixPath.resolve(UnixPath.java:43)
[error] 	at sbt.internal.io.SourceModificationWatch$.expandEvent(SourceModificationWatch.scala:70)
[error] 	at sbt.internal.io.SourceModificationWatch$.$anonfun$watch$1(SourceModificationWatch.scala:
28)
[error] 	at scala.collection.TraversableLike.$anonfun$map$1(TraversableLike.scala:234)
[error] 	at scala.collection.immutable.List.foreach(List.scala:389)
[error] 	at scala.collection.TraversableLike.map(TraversableLike.scala:234)
[error] 	at scala.collection.TraversableLike.map$(TraversableLike.scala:227)
[error] 	at scala.collection.immutable.List.map(List.scala:295)
[error] 	at sbt.internal.io.SourceModificationWatch$.watch(SourceModificationWatch.scala:28)
[error] 	at sbt.Watched$.liftedTree1$1(Watched.scala:106)
[error] 	at sbt.Watched$.executeContinuously(Watched.scala:104)
[error] 	at sbt.BasicCommands$.$anonfun$continuous$2(BasicCommands.scala:231)
[error] 	at sbt.CommandUtil$.withAttribute(CommandUtil.scala:49)
[error] 	at sbt.BasicCommands$.$anonfun$continuous$1(BasicCommands.scala:229)
[error] 	at sbt.Command$.$anonfun$applyEffect$4(Command.scala:134)
[error] 	at sbt.Command$.$anonfun$applyEffect$2(Command.scala:130)
[error] 	at sbt.MainLoop$.processCommand(MainLoop.scala:153)
[error] 	at sbt.MainLoop$.$anonfun$next$2(MainLoop.scala:136)
[error] 	at sbt.State$$anon$1.runCmd$1(State.scala:242)

It seems indeed WatchEvent.context() may be null (https://docs.oracle.com/javase/7/docs/api/java/nio/file/WatchEvent.html), and I suspect UnixPath.resolve does not accept null.

[felher]

This is very annoying to me, but I have neither the knowledge nor the time to look into it. I'm willing to spend 50 bucks to help fix this issue and improve SBT. So if anyone wants to take a shot at it: https://www.bountysource.com/issues/53003420-watchevent-context-may-be-null

[dwijnand]

@felher nice! I've added the "help wanted" label to draw attention to it.

[eed3si9n]

Not sure if it's related but there's #138 and sbt/sbt#4052 for macOS.

[dwijnand]

fixed in #140, which is due in sbt/io 1.1.7 and probably sbt 1.1.4.

[felher]

Great. Can I already test hat? Did it make it into 1.1.4? :)

[dwijnand]

no sorry sbt/io 1.1.7 wasn't updated in sbt 1.1.4, so this will be either sbt 1.1.5 or sbt 1.2.0.