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Remove fixme part about guards and pattern matching from StyleGuide (#30787)

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Muskan Gupta 2021-10-25 21:30:41 +05:30 • committed by GitHub
parent 33052e3abc
commit 4d14c6f977
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2 changed files with 3 additions and 47 deletions
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39
akka-actor-typed-tests/src/test/scala/docs/akka/typed/StyleGuideDocExamples.scala
View file

@ -460,46 +460,13 @@ object StyleGuideDocExamples {
final case class GetValue(replyTo: ActorRef[Value]) extends Command
final case class Value(n: Int)
//#messages-sealed
def apply(countDownFrom: Int, notifyWhenZero: ActorRef[Done]): Behavior[Command] =
new CountDown(notifyWhenZero).counterWithGuard(countDownFrom)
}
private class CountDown(notifyWhenZero: ActorRef[Done]) {
class CountDown() {
import CountDown._
private def counterWithGuard(remaining: Int): Behavior[Command] = {
//#pattern-match-guard
// no exhaustiveness check because of guard condition
// FIXME not true anymore since Scala 2.13.5
Behaviors.receiveMessagePartial {
case Down if remaining == 1 =>
notifyWhenZero.tell(Done)
zero
case Down =>
counter(remaining - 1)
}
//#pattern-match-guard
}
@nowarn
private def counter(remaining: Int): Behavior[Command] = {
//#pattern-match-without-guard
// `@unchecked` for Scala 3, which doesn't support @nowarn
Behaviors.receiveMessage(x =>
(x: @unchecked) match {
case Down =>
if (remaining == 1) {
notifyWhenZero.tell(Done)
zero
} else
counter(remaining - 1)
})
//#pattern-match-without-guard
}
//#pattern-match-unhandled
private val zero: Behavior[Command] = {
val zero: Behavior[Command] = {
Behaviors.receiveMessage {
case GetValue(replyTo) =>
replyTo ! Value(0)
@ -513,7 +480,7 @@ object StyleGuideDocExamples {
@nowarn
object partial {
//#pattern-match-partial
private val zero: Behavior[Command] = {
val zero: Behavior[Command] = {
Behaviors.receiveMessagePartial {
case GetValue(replyTo) =>
replyTo ! Value(0)

11
akka-docs/src/main/paradox/typed/style-guide.md
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@ -390,17 +390,6 @@ in the pattern match and return `Behaviors.unhandled`.
Scala
: @@snip [StyleGuideDocExamples.scala](/akka-actor-typed-tests/src/test/scala/docs/akka/typed/StyleGuideDocExamples.scala) { #pattern-match-unhandled }
One thing to be aware of is the exhaustiveness check is not enabled when there is a guard condition in any of the
pattern match cases.
Scala
: @@snip [StyleGuideDocExamples.scala](/akka-actor-typed-tests/src/test/scala/docs/akka/typed/StyleGuideDocExamples.scala) { #pattern-match-guard }
Therefore, for the purposes of exhaustivity checking, it is be better to not use guards and instead move the `if`s after the `=>`.
Scala
: @@snip [StyleGuideDocExamples.scala](/akka-actor-typed-tests/src/test/scala/docs/akka/typed/StyleGuideDocExamples.scala) { #pattern-match-without-guard }
It's recommended to use the `sealed` trait and total functions with exhaustiveness check to detect mistakes
of forgetting to handle some messages. Sometimes that can be inconvenient and then you can use a `PartialFunction`
with `Behaviors.receivePartial` or `Behaviors.receiveMessagePartial`