How to set gradle subproject artifact as task input? - gradle

Question

My gradle build has a subproject with a task that produces a file
$ ./gradlew :strings:tokenizeStrings # creates strings/string_tokens.csv
then in my root project I have a task which consumes that file
tasks.generateLocalizationFiles {
inputTokensCsvFile.set(layout.projectDirectory.file("strings/string_tokens.csv"))
}
this works, but since gradle doesn't know about the dependency, it only works if I run the two tasks manually in the right order
$ ./gradlew :strings:tokenizeStrings
$ ./gradlew :generateLocalizationFiles
I want to add the proper dependency to gradle so that I can run just :generateLocalizationFiles and it will go into the subproject and do whatever it needs to. But I can't figure out the right way to do it.
What I've tried:
Following Simple sharing of artifacts between projects, I tried adding a consumable configuration to the suproject build script
val localizationData by configurations.creating {
isCanBeConsumed = true
isCanBeResolved = false
}
tasks.tokenizeStrings {
artifacts {
add("localizationData", outputTokensCsvFile) {
builtBy(this)
}
}
}
and then a resolvable configuration plus the dependency to the root project build script
val localizedStringData by configurations.creating {
isCanBeConsumed = false
isCanBeResolved = true
}
// hook up our resolvable configuration to the strings' consumable configuration
dependencies {
localizedStringData(project(mapOf(
"path" to ":strings",
"configuration" to "localizationData")
))
}
tasks.generateLocalizationFiles {
dependsOn(localizedStringData)
inputTokensCsvFile.set(localizedStringData.singleFile)
}
but that fails, seemingly because the consumable configuration is not populated?
Caused by: java.lang.IllegalStateException: Expected configuration ':localizedStringData' to contain exactly one file, however, it contains no files.

Answer 1

You need to add the outgoing artifact directly in the subproject build script, not inside the task configuration (which is only run lazily). You also don't need builtBy if you're using a RegularFileProperty for the artifact.
val localizationData by configurations.creating {
isCanBeConsumed = true
isCanBeResolved = false
}
artifacts {
add("localizationData", tasks.tokenizeStrings.flatMap { it.outputTokensCsvFile })
}
The trick is to use flatMap to lazily access the task. You should similarly use map when passing it to the task resolving the data. That allows for lazy task creation and implicitly tells gradle about the dependency between the two:
tasks.generateLocalizationFiles {
inputTokensCsvFile.set(localizedStringData.elements.map { it.first().asFile })
}
This still feels somewhat hacky, since it would be very clumsy if you wanted to repeat this for many artifacts, but it does seem to be the idiomatic way of doing it in gradle since it doesn't require any explicit dependency creation via builtBy/dependsOn.