Best practices for tasks docs.gradle.org/current/userguide/best_practices_tasks.html#… shows this piece of code

inputs.file(tasks.named<SimplePrintingTask>("helloWorld").map { messageFile })

do you need that in addition to configuring the inputs of the new task or does gradle figure that out automatically if you use an input file with the same path as the other task's output file?

That code looks wrong. I don't think it works. 🤔 I assume it was meant to configure the inputs and should look like this IMO:

tasks.register("translateGood", SimpleTranslationTask) {
    messageFile.set(tasks.named("helloWorld", SimplePrintingTask).flatMap { it.messageFile })
}

Explanation: • First

messageFile

is the one from SimpleTranslationTask • You set that to the

messageFile

output of SimplePrintingTask, preserving both the information which file you want and which task produces it. It's also an unfortunate choice to call it

messageFile

in both example tasks.

exactly, that also confused me

Yes. The

flatMap

gives you a

Provider<RegularFile>

that not only points at the path, but also has the information which task produces the file.

It at most auto-detects under some conditions that you use the output of the other task without dependency or ordering constraint. That's the situation where you get the bad advice by Gradle to add one explicitly.

IIUC, this will work because the convention value is the same in both tasks, but Gradle won't automatically detect the dependency (actually, it will and tell you that it's wrong and won't be used and you should fix it (by explicitly configuring the task dependency as shown here): docs.gradle.org/current/userguide/validation_problems.html#…) so you have to tell it, and

inputs.file()

is finer-grained than `dependsOn()`; but this is a bad example anyway. What you should do is indeed configure the input property to the output property of the other task, with a provider value that carries the task dependency.

And someone™ should open a ticket or pull-request to update this bad example