Creating File using `resourceGenerators` - scala

Question

Given:
$cat build.sbt
scalaVersion := "2.12.1"
resourceGenerators in Compile += Def.task {
val file = (resourceManaged in Compile).value / "demo" / "myapp.properties"
val contents = "name=%s\nversion=%s".format(name.value,version.value)
IO.write(file, contents)
Seq(file)
}.taskValue
$sbt compile
[info] Set current project to sbt_testing (in build file:/home/kmeredith/src/sbt_testing/)
[info] Updating {file:/home/kmeredith/src/sbt_testing/}sbt_testing...
[info] Resolving jline#jline;2.14.1 ...
[info] Done updating.
[success] Total time: 1 s, completed Dec 23, 2016 9:14:50 AM
My understanding is that a myapp.properties file should been created during the compile task.
But, I saw no such file created:
$find . -name *.properties
./target/resolution-cache/default/sbt_testing_2.12/0.1-SNAPSHOT/resolved.xml.properties
Please explain to me how to generate the myapp.properties.

Answer 1

You have the wrong expectation regarding the triggering of the resource generation - running compile does not trigger it (compiles existing sources but not generated ones!), but if you execute test or run, it will be generated:
$sbt clean compile
[success] Total time: 0 s, completed Dec 23, 2016 5:39:28 PM
[info] Updating {file:/home/tzachz/dev/sbt_testing/}sbt_testing...
[info] Done updating.
[info] Compiling 25 Scala sources to /home/tzachz/dev/sbt_testing/target/scala-2.11/classes...
[success] Total time: 24 s, completed Dec 23, 2016 5:39:52 PM
$find . -name "*.properties"
zsh: no matches found: *.properties
$sbt run
// ...
$find . -name "*.properties"
./target/scala-2.11/resource_managed/main/demo/myapp.properties
./target/scala-2.11/classes/demo/myapp.properties