Setting cannot depend on a task when adding logging to setting key - scala

Question

I am updating an sbt plugin which has a SettingKey from the fm-sbt-s3-resolver. I have made some progress on explicitly adding the needed setting as a side effect of the question here:
Logging from an sbt plugin
object MyPlugin {
override def requires = S3ResolverPlugin
override def trigger = allRequirements
override lazy val globalSettings = Seq(
resolvers ++= repos,
publishMavenStyle := true,
S3ResolverPlugin.autoImport.s3CredentialsProvider := {bucket: String =>
new AWSCredentialsProviderChain(
new EnvironmentVariableCredentialsProvider(),
PropertyFilesCredentialProvider.create(bucket, streams.value.log)
)
}
)
}
When I try to add logging using streams.value.log, sbt throws an error:
[error] A setting cannot depend on a task
[error] PropertyFilesCredentialProvider.create(bucket, streams.value.log)

Answer 1

In this case, you need to depend on setting sLog instead of task streams.
import sbt._
import sbt.Keys._
object Logs extends AutoPlugin {
object autoImport {
val settingLog = settingKey[Unit]("Uses setting sLog")
val taskLog = taskKey[Unit]("Uses task streams log")
}
import autoImport._
override def trigger = allRequirements
override def projectSettings: Seq[Def.Setting[_]] = Seq(
settingLog := { sLog.value.info("Logging on settings execution") },
taskLog := { streams.value.log.info("Logging on task execution") }
)
}
The difference with settingLog is the it will log when sbt boots.
~/w/t/stackoverflow $ sbt
[info] Logging on settings execution
Repeated calls to settingLog will not produce any logging anymore. But taskLog will print a log every time you call it