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Implement ZManaged.memoize #5347

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Merged
merged 1 commit into from
Aug 9, 2021
Merged

Implement ZManaged.memoize #5347

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53 changes: 53 additions & 0 deletions core-tests/shared/src/test/scala/zio/ZManagedSpec.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -1515,6 +1515,59 @@ object ZManagedSpec extends ZIOBaseSpec {
} yield res1 && res2 && res3
} @@ zioTag(interruption)
),
suite("memoize")(
testM("resources are properly acquired and released") {
for {
ref <- Ref.make[Map[Int, (Int, Int)]](Map.empty)
acquire = (n: Int) =>
ref.update { map =>
map.getOrElse(n, (0, 0)) match {
case (acquired, released) => map + (n -> ((acquired + 1, released)))
}
}
release = (n: Int) =>
ref.update { map =>
map.getOrElse(n, (0, 0)) match {
case (acquired, released) => map + (n -> ((acquired, released + 1)))
}
}
managed = (n: Int) => ZManaged.make_(acquire(n))(release(n))
_ <- ZManaged.memoize(managed).use { memoized =>
ZIO.foreachPar_(0 to 100)(n => memoized(n % 8))
}
map <- ref.get
} yield assert(map.keys)(equalTo(Set(0, 1, 2, 3, 4, 5, 6, 7))) &&
assert(map.values.map(_._1))(forall(equalTo(1))) &&
assert(map.values.map(_._2))(forall(equalTo(1)))
},
testM("resources are properly released in the event of interruption") {
for {
ref <- Ref.make[Map[Int, (Int, Int)]](Map.empty)
acquire = (n: Int) =>
ref.update { map =>
map.getOrElse(n, (0, 0)) match {
case (acquired, released) => map + (n -> ((acquired + 1, released)))
}
}
release = (n: Int) =>
ref.update { map =>
map.getOrElse(n, (0, 0)) match {
case (acquired, released) => map + (n -> ((acquired, released + 1)))
}
}
managed = (n: Int) => ZManaged.make_(acquire(n))(release(n))
fiber <- ZManaged
.memoize(managed)
.use { memoized =>
ZIO.foreachPar_(0 to 100)(n => memoized(n % 8) *> ZIO.never)
}
.fork
_ <- fiber.interrupt
map <- ref.get
} yield assert(map.values.map(_._1))(forall(equalTo(1))) &&
assert(map.values.map(_._2))(forall(equalTo(1)))
}
),
suite("merge")(
testM("on flipped result") {
val managed: Managed[Int, Int] = ZManaged.succeed(1)
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23 changes: 23 additions & 0 deletions core/shared/src/main/scala/zio/ZManaged.scala
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Original file line number Diff line number Diff line change
Expand Up @@ -2204,6 +2204,29 @@ object ZManaged extends ZManagedPlatformSpecific {
f(a, b, c, d)
}

/**
* Returns a memoized version of the specified resourceful function in the
* context of a managed scope. Each time the memoized function is evaluated
* a new resource will be acquired, if the function has not already been
* evaluated with that input, or else the previously acquired resource will
* be returned. All resources acquired by evaluating the function will be
* released at the end of the scope.
*/
def memoize[R, E, A, B](f: A => ZManaged[R, E, B]): ZManaged[Any, Nothing, A => ZIO[R, E, B]] =
for {
fiberId <- ZIO.fiberId.toManaged_
ref <- Ref.makeManaged[Map[A, Promise[E, B]]](Map.empty)
scope <- ZManaged.scope
} yield a =>
ref.modify { map =>
map.get(a) match {
case Some(promise) => (promise.await, map)
case None =>
val promise = Promise.unsafeMake[E, B](fiberId)
(scope(f(a)).map(_._2).to(promise) *> promise.await, map + (a -> promise))
}
}.flatten

/**
* Merges an `Iterable[ZManaged]` to a single `ZManaged`, working sequentially.
*/
Expand Down