its simple

.java files are compiled as java

.kt files are compiled using kotlinc

@bmsantos: Yes but how do they determine in which order to compile them?

Right now kobalt does it the lazy way and forces the developer to put these files in projects and then specify the dependencies between projects

it should not matter. each package/jar should compile all java files first and then kotlin files

It does matter: I give you

A.java

and

B.kt

, how do you determine which one to compile first?

I would think that you compile all java first

then you compile all kt

Why? That’s arbitrary.

the compiler should know what to do

Maybe B.kt depends on A

but the compiler only knows files it can compile

javac

doesn’t see

B.kt

and

kotlinc

doesn’t see

A.java

Oh, almost forgot, there's this: https://github.com/cbeust/kobalt/pull/83 I do not have access to a Windows machine I could install cygwin onto, so if anyone could check if this works in cygwin, I'd be grateful simple smile

if you compile all java files first, then kotlinc should find A.java in the classpath

But what about Java files that depend on Kotlin files?

I was about to express that concern

yes, in that direction it might be a problem

The only correct way to do this is to analyze the imports, build a tree of dependencies and invoke javac/kotlin for each batch of files

not unfeasible but not trivial either

1) javac A.java C.java 2) kotlinc B.kt 3) javac D.java E.java 4) kotlinc F.kt (assuming a worst case situation)

Even analyzing the imports might not be enough since this will miss fully qualified types inside the source

I remember I had the same problem with groovy once upon a time: java depended on groovy and vice versa, in gradle it was easily solved by using groovyc for both source-sets, I guess that's a groovyc feature kotlinc doesn't have.

Yes,I was hoping kotlinc would know to invoke javac on java files but Dmitry told me that wasn’t the case

Which is why it works in IDEA (since it knows everything about the sources) but I’m surprised to hear gradle or maven might have that too. I’m suspecting either they use their PSI API outside of IDEA or they just make simplifying assumptions like: compile all .java first, hope it works

So right now with kobalt, I’m asking you to clean up your mess and put files in separate projects simple smile

(actually they can be in overlapping projects, they just need to be compiled in a certain order)

it's a feature of the compiler, gradle/maven/whatever doesn't care in this instance. when configured like this groovyc parses java files and makes note on all unavailable files, then parses and compiles groovy, gradually resolving those noted dependencies on groovy from java while also resolving groovy's dependencies on java classes it has already parsed, a bit slow, but it works.

You might want to have a look at the maven mojo: https://github.com/JetBrains/kotlin/blob/master/libraries/tools/kotlin-maven-plugin/src/main/java/org/jetbrains/kotlin/maven/KotlinCompileMojoBase.java