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And to make things even more interesting: There could be a file with the version string in a sub-project which should be used over the "general" version file, so the hierarchy would be: Generic version file < Project-specific version file < Environment variable < Gradle property.

You would express that in a

Provider

chain, starting at the most important one and then do a

Provider.orElse

chain.

Thanks, Louis! I thought along those lines, too. How would that work with

RegularFileProperty

and checking that the files (don't) exist? I think something like this wouldn't work, would it?

def myVersion = project.objects.fileProperty().fileValue(project.file("specific"))
  .orElse(project.objects.fileProperty().fileValue(project.file("global")))
  .map(file -> "read version string from file")
  .orElse("default")

I did not try the code, but it should work. However, you have to begin with the Gradle property, since it wins when present, then go down in priority order, finishing with the files and possibly a default convention.

It's all working as advertised, thanks! 🙂

ext {
    def env = providers.environmentVariable("MY_VERSION")
    def specificFile = providers.fileContents(layout.projectDirectory.file("specific")).asText
    def globalFile = providers.fileContents(layout.projectDirectory.file("global")).asText

    myVersion = env.orElse(specificFile.orElse(globalFile)).getOrElse("default")
}

tasks.register('printVersion') {
    it.doLast {
        project.println(myVersion)
    }
}

Example:

# MY_VERSION=env ./gradlew -q printVersion
env
# ./gradlew -q printVersion
specific
# rm specific && ./gradlew -q printVersion
global
# rm global && ./gradlew -q printVersion
default