Custom mainclass

[jkutner]

The PR allows for a custom main class as an arg to the bash script. The primary motivation for this is adding the ability to run something like the following to get a repl for an app:

./target/universal/stage/bin/my-app -main scala.tools.nsc.MainGenericRunner -usejavacp

The above requires adding the following to your build.sbt of course:

libraryDependencies <+= scalaVersion("org.scala-lang" % "scala-compiler" % _ )

If this PR is acceptable I will take the time to add this to the bat-template as well.

[lightbend-cla-validator]

Hi @jkutner,

Thank you for your contribution! We really value the time you've taken to put this together.

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[jkutner]

This would fix #80 I believe

[muuki88]

LGTM. This should be easily testable? Can you provide a test within in the universal
suite which builds a simple app with two executable scala files and run both in the test
and check the output?

It would be even more awesome if you could add a little documentation for it.
See Developer Guide for more details on how to build/check the docs.

[jkutner]

sure. i'll do both and update the PR

[jkutner]

I have tried to create test for this, and I'm having trouble. I think I don't understand the testing framework. Can you look at my test project under universal/staging-custom-main and tell me what to do next?

[kardapoltsev]

Now you could run your test with
scripted universal/staging-custom-main
Also you could add custom task to bulid.sbt and implement your own tests (see other tests for examples).

[jkutner]

I tried to follow the example of the existing tests, but I'm stuck testing for my bin/ dir and I don't know why. My test fails with this error no matter what I try:

Caused by: java.lang.RuntimeException: Test script error: File(s) did not exist: [ /var/folders/mk/w8gpswvs1tl70bhj60s4kvy40000gn/T/sbt_cdc73125/staging-custom-main/stage-custom-main-0.1.0/bin ]

Am I doing something obviously wrong?

[kardapoltsev]

Some suggestions about debugging. Are you sure where do you extract zip? Try to add $ pause command after unzip and check real file tree.

[muuki88]

Ah, nice trick with the $ pause. I'm using good old println, like this

TaskKey[Unit]("print-dir") <<= (baseDirectory, streams) map { (t, streams) =>
  streams.log.warn("----------------------------")
  (t).listFiles foreach (f => streams.log.warn(f.getAbsolutePath))
}

The error

Anyway, I found the error. The problem is that there are multiple mainClass classes.
The makeUniversalBinScript in JavaApp is responsible for creating the correct mappings.
However it seems to get confused with multiple main classes.

The fix

Setting a specific main class helps.

mainClass in Compile := Some("Main")

Note that is must be scoped to Compile!

[jkutner]

Thanks @kardapoltsev and @muuki88 -- i am wiser now :) The test is passing. I will update the docs soon.

[muuki88]

Brilliant! Thanks @jkutner

[muuki88]

Merged into v0.7.x