Doesn't see managedSources unless explicitly invoked

I'm using the SBT protobuf plugin together with sbteclipse, on SBT 1.0.1.

addSbtPlugin("com.github.gseitz" % "sbt-protobuf" % "0.6.3")
addSbtPlugin("com.typesafe.sbteclipse" % "sbteclipse-plugin" % "5.2.2")

Now it seems that sbteclipse doesn't "see" the extra managedSources that .enablePlugins(ProtobufPlugin) puts into a project configuration, unless that's explicitly invoked before running eclipse.

In other words, in a clean workspace, sbt eclipse will generate a correct .classpath. But running it again will not have the src_managed generated protobuf sources in it. Touching a .proto file, opening the SBT console, and typing compile and then eclipse will once more yield the correct result.

I stumbled onto this when doing an SBT 1.0 upgrade... I'm unsure whether this worked before, or whether I'm just missing something extra in my project. I'd expect that managedSources is interrogated by sbt eclipse before generating the .classpath though, so I don't know what's up.

Reproduce the issue in a clean workspace with sbt 1.0.1, sbt-protobuf 0.6.3, and sbteclipse 5.2.2 by running sbt eclipse repeatedly, then compare the generated .classpath. Start by tracing how sbteclipse reads managedSources; done means repeated eclipse runs include the generated src_managed protobuf sources without a prior compile.