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author | Viktor Klang <viktor.klang@gmail.com> | 2014-09-26 12:05:37 +0200 |
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committer | Viktor Klang <viktor.klang@gmail.com> | 2014-10-20 23:55:44 +0200 |
commit | fa0743c32338f147eaf7a5d69566bbc15d193f85 (patch) | |
tree | 24f6b6d5cbab337174d48f0d0876ac0de93141f5 /src/library/scala/concurrent/Promise.scala | |
parent | c0ceffb865ff4b2146aacec547cc42bb7605ee93 (diff) | |
download | scala-fa0743c32338f147eaf7a5d69566bbc15d193f85.tar.gz scala-fa0743c32338f147eaf7a5d69566bbc15d193f85.tar.bz2 scala-fa0743c32338f147eaf7a5d69566bbc15d193f85.zip |
Add missing canonical combinators:
- `def transform[S](f: Try[T] => Try[S])(implicit executor: ExecutionContext): Future[S]`
- `def transformWith[S](f: Try[T] => Future[S])(implicit executor: ExecutionContext): Future[S]`
- `def flatten[S](implicit ev: T <:< Future[S]): Future[S]`
- `def zipWith[U, R](that: Future[U])(f: (T, U) => R)(implicit executor: ExecutionContext): Future[R]`
Add missing utilities:
- `val unit: Future[Unit]` in `object Future`
- `object never extends Future[Nothing]` in `object Future`
- `def defaultBlockContext: BlockContext` in `object BlockContext`
- `def toString: String` on stdlib implementations of `Future`
Refactors:
- the `scala.concurrent.Future` trait to not explicit create any `Promises`,
so that implementations can control implementation type,
this is mainly facilitated through adding of the `transform` and `transformWith` methods.
- the implementation of `ExecutionContextImpl` has been cleaned up
- the `scala.concurrent.impl.DefaultPromise` has been reimplemented to not use `sun.misc.Unsafe`
Securing:
- Add a self-check in `completeWith` and `tryCompleteWith` to avoid cycles in trait Promise
- Capping the maximum number of threads for the global `ExecutionContext` to the max parallelism
- Implementing (almost) all `Future` combinators on `transformWith` and `transform` means
that `DefaultPromise` linking works on both `(flat)map` and `recover(With)`
- Nested `blocking {}` should not spawn extra threads beyond the first.
Removes:
- the private `internalExecutor` method in favor of an import in trait `Future`
- the private `internalExecutor` method in favor of an import in trait `Promise`
- the `AtomicReferenceFieldUpdater` in `AbstractPromise` since we're using `Unsafe`
- `scala.concurrent.impl.Future` is no longer needed
Deprecates:
- `Future.onSuccess` - discourage the use of callbacks
(and is also redundant considering `foreach` and `onComplete`)
- `Future.onFailure` - discourage the use of callbacks
(and is also redundant considering `onComplete` and `failed.foreach`)
- `ExecutionContext.prepare` - it was ill specced and it is too easy to forget to call it
(or even know when to call it or call it more times than needed)
- All classes in scala.concurrent.forkjoin. Scala 2.12 will be Java 8+ and as such the jsr166e
should be used as included in java.util.concurrent.
Reimplements:
- `failed` - in terms of `transform`
- `map` - in terms of `transform`
- `flatMap` - in terms of `transformWith`
- `recover` - in terms of `transform`
- `recoverWith` - in terms of `transformWith`
- `zip` - in terms of `flatMap` + `map`
- `fallbackTo` - in terms of `recoverWith` + `recoverWith`
- `andThen` - in terms of `transform`
Miscellaneous:
- Giving the threads of `ExecutionContext.global` sensible names
- Optimizes `object Future.successful` and `object Future.failed` are now separate implementations,
to optimize for the result, avoiding doing work for the "other branch".
- Optimizes `compressedRoot()` by avoiding double-calls to volatile get.
Documentation:
- Almost all methods on `Future` and `Promise` have been revisited and had their ScalaDoc updated
Tests:
- Yes
Diffstat (limited to 'src/library/scala/concurrent/Promise.scala')
-rw-r--r-- | src/library/scala/concurrent/Promise.scala | 16 |
1 files changed, 7 insertions, 9 deletions
diff --git a/src/library/scala/concurrent/Promise.scala b/src/library/scala/concurrent/Promise.scala index eb8044ed3b..dc4376eba4 100644 --- a/src/library/scala/concurrent/Promise.scala +++ b/src/library/scala/concurrent/Promise.scala @@ -26,12 +26,6 @@ import scala.util.{ Try, Success, Failure } * Note: Using this method may result in non-deterministic concurrent programs. */ trait Promise[T] { - - // used for internal callbacks defined in - // the lexical scope of this trait; - // _never_ for application callbacks. - private implicit def internalExecutor: ExecutionContext = Future.InternalCallbackExecutor - /** Future containing the value of this promise. */ def future: Future[T] @@ -67,7 +61,9 @@ trait Promise[T] { * @return This promise */ final def completeWith(other: Future[T]): this.type = { - other onComplete { this complete _ } + if (other ne this.future) { // this completeWith this doesn't make much sense + other.onComplete(this complete _)(Future.InternalCallbackExecutor) + } this } @@ -76,7 +72,9 @@ trait Promise[T] { * @return This promise */ final def tryCompleteWith(other: Future[T]): this.type = { - other onComplete { this tryComplete _ } + if (other ne this.future) { // this tryCompleteWith this doesn't make much sense + other.onComplete(this tryComplete _)(Future.InternalCallbackExecutor) + } this } @@ -142,5 +140,5 @@ object Promise { * @tparam T the type of the value in the promise * @return the newly created `Promise` object */ - def fromTry[T](result: Try[T]): Promise[T] = new impl.Promise.KeptPromise[T](result) + def fromTry[T](result: Try[T]): Promise[T] = impl.Promise.KeptPromise[T](result) } |