[api breaking]Make some operators to accept SignalProducerConvertible conforming types #611

ra1028 · 2018-02-22T21:15:29Z

Continuation from #610

These operators now accept SignalProducerConvertible conforming types.
SignalProducer.merge(with:)
SignalProducer.concat
SignalProducer.prefix
SignalProducer.then
SignalProducer.and
SignalProducer.or
SignalProducer.zip(with:)
SignalProducer.sample(with:)
SignalProducer.sample(on:)
SignalProducer.take(until:)
SignalProducer.take(untilReplacement:)
SignalProducer.skip(until:)
SignalProducer.flatMap
SignalProducer.flatMapError
SignalProducer.combineLatest(with:)
Signal.flatMap
Signal.flatMapError
Signal.withLatest(from:)
Property.init(initial:then:)

Checklist

Updated CHANGELOG.md.

…rror, Signal.flatMapError are now accept SignalProducerConvertible conforming type

…onvertible conforming type

…conforming type

andersio · 2018-02-25T14:17:06Z

Sources/SignalProducer.swift

@@ -2143,7 +2143,7 @@ extension SignalProducer {
 	///
 	/// - returns: A producer that sends events from `self` and then from
 	///            `replacement` when `self` completes.
-	public func then<U>(_ replacement: SignalProducer<U, Error>) -> SignalProducer<U, Error> {
+	public func then<U, Replacement: SignalProducerConvertible>(_ replacement: Replacement) -> SignalProducer<U, Error> where Replacement.Value == U, Replacement.Error == Error {


U can be replaced by Replacement.Value.

andersio · 2018-02-25T14:17:19Z

Sources/SignalProducer.swift

 		return _then(replacement)
 	}

 	// NOTE: The method below is the shared implementation of `then(_:)`. The underscore
 	//       prefix is added to avoid self referencing in `then(_:)` overloads with
 	//       regard to the most specific rule of overload selection in Swift.

-	internal func _then<U>(_ replacement: SignalProducer<U, Error>) -> SignalProducer<U, Error> {
+	internal func _then<U, Replacement: SignalProducerConvertible>(_ replacement: Replacement) -> SignalProducer<U, Error> where Replacement.Value == U, Replacement.Error == Error {


andersio · 2018-02-25T14:17:55Z

Sources/SignalProducer.swift

@@ -2203,7 +2203,7 @@ extension SignalProducer where Error == NoError {
 	///
 	/// - returns: A producer that sends events from `self` and then from
 	///            `replacement` when `self` completes.
-	public func then<U, NewError>(_ replacement: SignalProducer<U, NewError>) -> SignalProducer<U, NewError> {
+	public func then<U, NewError, Replacement: SignalProducerConvertible>(_ replacement: Replacement) -> SignalProducer<U, NewError> where Replacement.Value == U, Replacement.Error == NewError {


Ditto. NewError can be replaced by Replacement.Error too.

andersio · 2018-02-25T14:18:23Z

Sources/SignalProducer.swift

+	///
+	/// - returns: A producer that sends events from `self` and then from
+	///            `replacement` when `self` completes.
+	public func then<Replacement: SignalProducerConvertible>(_ replacement: Replacement) -> SignalProducer<Value, NoError> where Replacement.Value == Value, Replacement.Error == NoError {


Why is there a new variant?

Probably because the type became ambiguous than before.
In the test, 4 errors occur including this line.

andersio · 2018-02-25T14:20:18Z

Sources/Flatten.swift

@@ -960,7 +963,7 @@ extension SignalProducer {
 	/// - parameters:
 	///   - transform: A closure that accepts emitted error and returns a signal
 	///                producer with a different type of error.
-	public func flatMapError<F>(_ transform: @escaping (Error) -> SignalProducer<Value, F>) -> SignalProducer<Value, F> {
+	public func flatMapError<F, Inner: SignalProducerConvertible>(_ transform: @escaping (Error) -> Inner) -> SignalProducer<Value, F> where Inner.Value == Value, Inner.Error == F {


F can be replaced by Inner.Error.

andersio · 2018-02-25T14:20:37Z

Sources/Flatten.swift

@@ -928,19 +928,22 @@ extension Signal {
 	/// - parameters:
 	///   - transform: A closure that accepts emitted error and returns a signal
 	///                producer with a different type of error.
-	public func flatMapError<F>(_ transform: @escaping (Error) -> SignalProducer<Value, F>) -> Signal<Value, F> {
+	public func flatMapError<F, Inner: SignalProducerConvertible>(_ transform: @escaping (Error) -> Inner) -> Signal<Value, F> where Inner.Value == Value, Inner.Error == F {


andersio · 2018-02-25T14:20:41Z

Sources/Flatten.swift

 		return Signal<Value, F> { observer, lifetime in
 			lifetime += self.observeFlatMapError(transform, observer, SerialDisposable())
 		}
 	}

-	fileprivate func observeFlatMapError<F>(_ handler: @escaping (Error) -> SignalProducer<Value, F>, _ observer: Signal<Value, F>.Observer, _ serialDisposable: SerialDisposable) -> Disposable? {


andersio · 2018-02-25T14:22:32Z

CHANGELOG.md

@@ -5,7 +5,7 @@
 1. New property operator: `filter` (#586, kudos to @iv-mexx)
 1. New operator `merge(with:)` (#600, kudos to @ra1028)
 1. New operator `map(value:)` (#601, kudos to @ra1028)
-1. `SignalProducer.merge` now accepts any combination of `SignalProducerConvertible` conforming types (#610, kudos to @1028)
+1. `SignalProducer.merge`, `SignalProducer.concat`, `SignalProducer.prefix`, `SignalProducer.then`, `SignalProducer.flatMapError` `Signal.flatMapError`, `Signal.withLatest` and `Property.init(initial:values:)` are now accept `SignalProducerConvertible` conforming types (#610, #611, kudos to @1028)


Property.init(initial:then:).

ra1028 · 2018-02-25T15:54:51Z

@andersio
Amended 👍

NachoSoto · 2018-02-25T16:11:39Z

Tests/ReactiveSwiftTests/SignalProducerSpec.swift

@@ -3012,7 +3012,7 @@ class SignalProducerSpec: QuickSpec {
 					.combineLatest(SignalProducer<Int, NoError>.never.promoteError(),
 					               SignalProducer<Double, TestError>.never,
 					               SignalProducer<Float, NoError>.never.promoteError(),
-					               SignalProducer<UInt, POSIXError>.never.flatMapError { _ in .empty })
+					               SignalProducer<UInt, POSIXError>.never.flatMapError { _ in SignalProducer.empty })


I'd say this is a regression. I use this very often, so it's unfortunate it doesn't compile anymore... I wonder if adding static var empty to the protocol would still allow this?

Do you mean adding static var empty to the SignalProducerConvertible?
I think it can't be resolved without a contextual types😢

@NachoSoto
One of solution is to overload SignalProducer.flatMapError as below.
But I don't prefer this.

public func flatMapError<Inner: SignalProducerConvertible>(_ transform: @escaping (Error) -> Inner) -> SignalProducer<Value, Inner.Error> where Inner.Value == Value { return flatMapError { transform($0).producer } } public func flatMapError<NewError>(_ transform: @escaping (Error) -> SignalProducer<Value, NewError>) -> SignalProducer<Value, NewError> { return SignalProducer<Value, NewError> { observer, lifetime in let serialDisposable = SerialDisposable() lifetime += serialDisposable self.startWithSignal { signal, signalDisposable in serialDisposable.inner = signalDisposable _ = signal.observeFlatMapError(transform, observer, serialDisposable) } } }

@ra1028 I think it is a reasonable solution & should be applied to existing operators anticipating SignalProducerConvertible too. Contextual lookup plays an important role in expressivity.

That's said, please try if a default implementation of static var empty: SignalProducer<Value, Error> on the protocol works.

@andersio
Such protocol works to occur errors like the below.

extension SignalProducerConvertible { /// A producer for a Signal that immediately completes without sending any values. public static var empty: SignalProducer<Value, Error> { return .empty } }

Therefore, I'll overload existing operators anticipating SignalProducerConvertible.

I added an overloaded operator to flatMap and flatMapError for contextual lookup.
Is it also necessary for other operators that will passed SignalProducerConvertible?
IMO, there aren't many cases to pass empty directly like below.

producer.then(.empty)

It is not just .empty but also .init and generic expressions which is handful when contextual lookup & type inference work. So yes.

@andersio
done 👍

mdiep · 2018-03-19T12:35:01Z

CHANGELOG.md

@@ -5,7 +5,7 @@
 1. New property operator: `filter` (#586, kudos to @iv-mexx)
 1. New operator `merge(with:)` (#600, kudos to @ra1028)
 1. New operator `map(value:)` (#601, kudos to @ra1028)
-1. `SignalProducer.merge` now accepts any combination of `SignalProducerConvertible` conforming types (#610, kudos to @1028)
+1. `SignalProducer.merge`, `SignalProducer.concat`, `SignalProducer.prefix`, `SignalProducer.then`, `SignalProducer.flatMapError` `Signal.flatMapError`, `Signal.withLatest` and `Property.init(initial:then:)` are now accept `SignalProducerConvertible` conforming types (#610, #611, kudos to @1028)


The are should be removed.

SignalProducer.merge, SignalProducer.concat, SignalProducer.prefix, SignalProducer.then, SignalProducer.flatMapError Signal.flatMapError, Signal.withLatest and Property.init(initial:then:) now accept SignalProducerConvertible conforming types (#610, #611, kudos to @1028)

@mdiep
Sorry for the late response.
Done:+1:

mdiep · 2018-03-19T12:36:10Z

Sources/Flatten.swift

+	/// - returns: A producer that will start `self` and then on completion of
+	///            `self` - will start `next`.
+	public func concat<Next: SignalProducerConvertible>(_ next: Next) -> SignalProducer<Value, Error> where Next.Value == Value, Next.Error == Error {
+		return concat(next.producer)
 	}


Why do we need 2 versions of all these operators?

To disambiguate when contextual lookup is used with these operators. Context: #611 (comment)

Ideally there should be a way of saying Next by default would be SignalProducer, for example. But there wasn't so the only option is relying on overloading.

mdiep · 2018-04-09T13:28:31Z

I think we'd want tests that exercise each of these at least once—for type inference if nothing else.

I'm going go to leave this for @andersio to review since he'll be more much familiar with any traps here.

…hen)

…lacement:), sample(with:), sample(on:), withLatest(from:), combineLatest(with:) and zip(with:)

ra1028 · 2018-04-26T20:04:47Z

@mdiep @andersio
I added tests for check able to use contextual lookup.

ra1028 added 5 commits February 23, 2018 05:49

SignalProducer.concat, SignalProducer.prefix, SignalProducer.flatMapE…

d95b7f2

…rror, Signal.flatMapError are now accept SignalProducerConvertible conforming type

Signal.withLatest, SignalProducer.then are now accept SignalProducerC…

b3a870b

…onvertible conforming type

Property.init(initial:then:) is now accept SignalProducerConvertible …

12b2280

…conforming type

Merge branch 'master' into feature/accept-SignalProducerConvertible

ffc84fa

Update CHANGELOG

756ecff

ra1028 changed the title ~~[wip][api breaking]Make some operators to accept SignalProducerConvertible conforming types~~ [api breaking]Make some operators to accept SignalProducerConvertible conforming types Feb 23, 2018

andersio added the api breaking label Feb 25, 2018

andersio requested changes Feb 25, 2018

View reviewed changes

ra1028 added 3 commits February 26, 2018 00:40

Remove unnecessary generic types

642bacc

Update CHANGELOG

efbbc56

Remove unnecessary generic type in SignalProducer.withLatest

a4e3572

NachoSoto reviewed Feb 25, 2018

View reviewed changes

ra1028 added 5 commits February 28, 2018 19:28

flatMapError contextual lookup

b4a83ff

flatMap contextual lookup

87e2b66

contextual lookup

f48faf1

and/or contextual lookup

95f677d

Remove unneeded white space

79841bb

andersio self-requested a review March 2, 2018 22:41

mdiep reviewed Mar 19, 2018

View reviewed changes

Update CHANGELOG

7abfae0

andersio added this to the 4.0 milestone Apr 15, 2018

ra1028 added 7 commits April 27, 2018 01:49

Add tests for prefix and concat

f676f11

Add tests for SignalProducer.flatMap and Signal.flatMap

9e0755b

Add tests for SignalProducer.flatMapError and Property.init(initial:t…

7338e5e

…hen)

Add tests for merge(with:), skip(until:), take(until:), take(untilRep…

980e690

…lacement:), sample(with:), sample(on:), withLatest(from:), combineLatest(with:) and zip(with:)

Add tests for then

b655947

Add tests for and, or

cf57671

Update ChangeLog

4b4da12

Remove empty line spaces

f5ca560

ra1028 force-pushed the feature/accept-SignalProducerConvertible branch from 182bda5 to f5ca560 Compare April 26, 2018 19:42

ra1028 added 2 commits April 27, 2018 04:49

Refactor

4f68145

Typo

2922cb8

andersio approved these changes May 27, 2018

View reviewed changes

andersio merged commit 9889269 into ReactiveCocoa:master May 27, 2018

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[api breaking]Make some operators to accept SignalProducerConvertible conforming types #611

[api breaking]Make some operators to accept SignalProducerConvertible conforming types #611

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[api breaking]Make some operators to accept SignalProducerConvertible conforming types #611

[api breaking]Make some operators to accept SignalProducerConvertible conforming types #611

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