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promoteError type inference. #413

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Merged
merged 3 commits into from
May 30, 2017
Merged

promoteError type inference. #413

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a706140
`promoteError` type inferrence.
andersio May 26, 2017
11f9322
Merge branch 'master' into promoteerror-v2
andersio May 29, 2017
90e438b
Test cases for `promoteError` type inference.
andersio May 30, 2017
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2 changes: 2 additions & 0 deletions CHANGELOG.md
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Original file line number Diff line number Diff line change
@@ -1,5 +1,7 @@
# master
*Please add new entries at the top.*
1. `promoteError` can now infer the new error type from the context. (#xxx, kudos to @andersio)

1. `promoteErrors(_:)` has been renamed to `promoteError(_:)`. (#408, kudos to @andersio)

# 1.1.3
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17 changes: 16 additions & 1 deletion Sources/Signal.swift
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Expand Up @@ -2405,7 +2405,7 @@ extension Signal where Error == NoError {
/// - _ An `ErrorType`.
///
/// - returns: A signal that has an instantiatable `ErrorType`.
public func promoteError<F: Swift.Error>(_: F.Type) -> Signal<Value, F> {
public func promoteError<F: Swift.Error>(_: F.Type = F.self) -> Signal<Value, F> {
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@NachoSoto NachoSoto May 27, 2017

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Awesome

return Signal<Value, F> { observer in
return self.observe { event in
switch event {
Expand All @@ -2422,6 +2422,21 @@ extension Signal where Error == NoError {
}
}

/// Promote a signal that does not generate failures into one that can.
///
/// - note: This does not actually cause failures to be generated for the
/// given signal, but makes it easier to combine with other signals
/// that may fail; for example, with operators like
/// `combineLatestWith`, `zipWith`, `flatten`, etc.
///
/// - parameters:
/// - _ An `ErrorType`.
///
/// - returns: A signal that has an instantiatable `ErrorType`.
public func promoteError(_: Error.Type = Error.self) -> Signal<Value, Error> {
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@NachoSoto NachoSoto May 27, 2017

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Wait why is this overload necessary?

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@andersio andersio May 27, 2017 •
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It isn't necessary, just that it allows one adds promoteError to everything in a brute force manner, while not yielding extra Signals in cases with the identical error types. Say if you do:

SignalProducer<Int, CocoaError>.combineLatest(
    SignalProducer<Int, CocoaError>.empty.promoteError(),
    SignalProducer<Int, NoError>.empty.promoteError()
)

The resulting Signal graph would be equivalent to:

SignalProducer<Int, CocoaError>.combineLatest(
    SignalProducer<Int, CocoaError>.empty,
    SignalProducer<Int, NoError>.empty.promoteError()
)

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@NachoSoto NachoSoto May 28, 2017

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I'm very much 👎 for that. Since when has RAC promoted brainless thinking? :P A user calling this operator when they shouldn't is likely an error and shouldn't be silenced IMO.

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@andersio andersio May 28, 2017 •
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Perhaps I should be more careful about my wordings. The overload does not add any capability, and is just a fast path when the compiler knows Self.Error is the Error of the return producer.

Say SignalProducer<Int, CocoaError>.empty.promoteError(CocoaError.self).

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@NachoSoto NachoSoto May 29, 2017

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Oooh that's right, because it's not possible to do negative conditions on extensions. This is a great idea then 👍

return self
}

/// Forward events from `self` until `interval`. Then if signal isn't
/// completed yet, fails with `error` on `scheduler`.
///
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17 changes: 16 additions & 1 deletion Sources/SignalProducer.swift
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Expand Up @@ -1397,10 +1397,25 @@ extension SignalProducer where Error == NoError {
/// - _ An `ErrorType`.
///
/// - returns: A producer that has an instantiatable `ErrorType`.
public func promoteError<F: Swift.Error>(_: F.Type) -> SignalProducer<Value, F> {
public func promoteError<F: Swift.Error>(_: F.Type = F.self) -> SignalProducer<Value, F> {
return lift { $0.promoteError(F.self) }
}

/// Promote a producer that does not generate failures into one that can.
///
/// - note: This does not actually cause failers to be generated for the
/// given producer, but makes it easier to combine with other
/// producers that may fail; for example, with operators like
/// `combineLatestWith`, `zipWith`, `flatten`, etc.
///
/// - parameters:
/// - _ An `ErrorType`.
///
/// - returns: A producer that has an instantiatable `ErrorType`.
public func promoteError(_: Error.Type = Error.self) -> SignalProducer<Value, Error> {
return self
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@NachoSoto NachoSoto May 27, 2017

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Ditto

}

/// Forward events from `self` until `interval`. Then if producer isn't
/// completed yet, fails with `error` on `scheduler`.
///
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