CODEWITHSUNDEEP
scalasbt
Klugscheißer
Klugscheißer

Reputation: 1624

List sbt `Task` tags

Is there a way to list the tags associated with a Task in sbt?

inspect and show don’t seem to have anything there.

Upvotes: 2

Views: 279

Answers (1)

Mario Galic
Mario Galic

Reputation: 48420

The cool and powerful aspect of sbt is that the build definition it generates is a regular Scala application meaning we can inspect its objects, like we would in any other Scala application, by simply invoking member methods to query their state. Executing sbt starts the REPL for the special DSL build language, however we can drop to a lower level by executing 

sbt consoleProject

to start true Scala REPL:

starts the Scala interpreter with access to your project definition and to sbt... consoleProject can be useful for creating and modifying your build in the same way that the Scala interpreter is normally used to explore writing code. Note that this gives you raw access to your build.

There exists a public tags method 

final case class Task[T](info: Info[T], work: Action[T]) {
  ...
  def tags: TagMap = info get tagsKey getOrElse TagMap.empty
}

so there must be a way to invoke it (even if there might not be a ready top level command for it such as inspect). Say we have the following tagged task definition in build.sbt

lazy val hello = taskKey[Unit]("Vulcan greeting")
hello := Def.task(println("Live long and prosper")).tag(Tags.CPU, Tags.Compile).value

After executing consoleProject our build definition is imported

scala> import _root_.scala.xml.{TopScope=>$scope}
import _root_.sbt._
import _root_.sbt.Keys._
import _root_.sbt.nio.Keys._
import _root_.sbt.ScriptedPlugin.autoImport._
import _root_.sbt.plugins.IvyPlugin
import _root_.sbt.plugins.JvmPlugin
import _root_.sbt.plugins.CorePlugin
import _root_.sbt.ScriptedPlugin
import _root_.sbt.plugins.SbtPlugin
import _root_.sbt.plugins.SemanticdbPlugin
import _root_.sbt.plugins.JUnitXmlReportPlugin
import _root_.sbt.plugins.Giter8TemplatePlugin
import $d408b7d79eabe42459a4.root
import currentState._
import extracted._
import cpHelpers._

Now we can make use of Extracted#get to get the TaskKey and explore it like so

scala> extracted.get(hello).tags
res1: sbt.ConcurrentRestrictions.TagMap = Map(Tag(cpu) -> 1, Tag(compile) -> 1)

Furthermore, note the import $d408b7d79eabe42459a4. We can use this object to access regular val/def members, for example, say we had defined in build.sbt

def helloTask = Def.task { println("Live long and prosper") } tag(Tags.CPU, Tags.Compile)

then we could access helloTask like so

scala> $d408b7d79eabe42459a4.helloTask.evaluate(structure.data).tags
res0: sbt.ConcurrentRestrictions.TagMap = Map(Tag(cpu) -> 1, Tag(compile) -> 1)

Both approaches show the required Map(Tag(cpu) -> 1, Tag(compile) -> 1).

Addressing the comment compileTask does not seem to be tagged thus

scala> get(Compile/compile).tags
res8: sbt.ConcurrentRestrictions.TagMap = Map()

however, for example, updateFull task is indeed tagged

updateFull := (updateTask tag (Tags.Update, Tags.Network)).value

hence

scala> get(updateFull).tags
res9: sbt.ConcurrentRestrictions.TagMap = Map(Tag(update) -> 1, Tag(network) -> 1)

Upvotes: 3

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