Presense of several main classes breaks docker:publishLocal

[unoexperto]

There are several subtle bugs in docker packager. I'll start with this issue first.

Presense of several main classes breaks docker:publishLocal.

Output directory /target/docker/stage/opt doesn't have bin directory with execution script. Example build.scala is here: https://github.com/cppexpert/sbt-docker-example/blob/eaf729a352a667c4637fb800fd6a90725b773235/project/build.scala

[unoexperto]

So... after 2 hours of debugging I came to solution that specifying main class in Compile package fixes the issue

      mainClass in Compile := Some("AnotherMain"),

It would be nice to sbt-native-packager to either prompt to choose main class or to fail with error instead of producing non-working docker image.

Thanks !

[muuki88]

This is a general thing with SBT. If there are multiple main classes then the 'mainClass in CompileisNone` because there is no way to determine the "right" main class.

However a warning would be a nice addition. I keep this issue as a feature request.

[unoexperto]

I think missing "bin" folder in produced docker image is a bug. It should not produce it at all if it cannot determine main class.

[unoexperto]

Is it fixed ?

[muuki88]

Nope, there isn't a warning yet. But there is another ticket where this issue fits in nicely: #633