-
Notifications
You must be signed in to change notification settings - Fork 166
Introduce mapError function #324
New issue
Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.
By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.
Already on GitHub? Sign in to your account
Open
clive819
wants to merge
11
commits into
apple:main
Choose a base branch
from
clive819:mapError
base: main
Could not load branches
Branch not found: {{ refName }}
Loading
Could not load tags
Nothing to show
Loading
Are you sure you want to change the base?
Some commits from the old base branch may be removed from the timeline,
and old review comments may become outdated.
Open
Changes from 2 commits
Commits
Show all changes
11 commits
Select commit
Hold shift + click to select a range
5fff2c6
Implement AsyncMapErrorSequence
clive819 e54d1fd
Address PR comments
clive819 79ef6cd
fix rookie mistake
clive819 4ba9c84
Adopt Failure type + add pitch doc
clive819 201c84c
fix typo
clive819 9d490f4
remove extra empty line
clive819 0193e84
address forums feedback
clive819 28938ea
address comments
clive819 cf62ea1
address comment
clive819 e3a0e1b
rename
clive819 8cb9ea8
clean up
clive819 File filter
Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
There are no files selected for viewing
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,99 @@ | ||
//===----------------------------------------------------------------------===// | ||
// | ||
// This source file is part of the Swift.org open source project | ||
// | ||
// Copyright (c) 2024 Apple Inc. and the Swift project authors | ||
// Licensed under Apache License v2.0 with Runtime Library Exception | ||
// | ||
// See https://swift.org/LICENSE.txt for license information | ||
// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors | ||
// | ||
//===----------------------------------------------------------------------===// | ||
|
||
extension AsyncSequence { | ||
|
||
/// Converts any failure into a new error. | ||
/// | ||
/// - Parameter transform: A closure that takes the failure as a parameter and returns a new error. | ||
/// - Returns: An asynchronous sequence that maps the error thrown into the one produced by the transform closure. | ||
/// | ||
/// Use the ``mapError(_:)`` operator when you need to replace one error type with another. | ||
public func mapError<ErrorType>(transform: @Sendable @escaping (Error) -> ErrorType) -> AsyncMapErrorSequence<Self, ErrorType> { | ||
.init(base: self, transform: transform) | ||
} | ||
} | ||
|
||
/// An asynchronous sequence that converts any failure into a new error. | ||
public struct AsyncMapErrorSequence<Base: AsyncSequence, ErrorType: Error>: AsyncSequence { | ||
|
||
public typealias AsyncIterator = Iterator | ||
public typealias Element = Base.Element | ||
|
||
private let base: Base | ||
private let transform: @Sendable (Error) -> ErrorType | ||
|
||
init( | ||
base: Base, | ||
transform: @Sendable @escaping (Error) -> ErrorType | ||
) { | ||
self.base = base | ||
self.transform = transform | ||
} | ||
|
||
public func makeAsyncIterator() -> Iterator { | ||
Iterator( | ||
base: base.makeAsyncIterator(), | ||
transform: transform | ||
) | ||
} | ||
} | ||
|
||
extension AsyncMapErrorSequence { | ||
|
||
/// The iterator that produces elements of the map sequence. | ||
public struct Iterator: AsyncIteratorProtocol { | ||
|
||
public typealias Element = Base.Element | ||
|
||
private var base: Base.AsyncIterator | ||
|
||
private let transform: @Sendable (Error) -> ErrorType | ||
|
||
init( | ||
base: Base.AsyncIterator, | ||
transform: @Sendable @escaping (Error) -> ErrorType | ||
) { | ||
self.base = base | ||
self.transform = transform | ||
} | ||
|
||
#if compiler(>=6.0) | ||
public mutating func next() async throws(ErrorType) -> Element? { | ||
do { | ||
return try await base.next() | ||
} catch { | ||
throw transform(error) | ||
} | ||
} | ||
|
||
@available(macOS 15.0, iOS 18.0, watchOS 11.0, tvOS 18.0, visionOS 2.0, *) | ||
public mutating func next(isolation actor: isolated (any Actor)?) async throws(ErrorType) -> Element? { | ||
do { | ||
return try await base.next(isolation: actor) | ||
} catch { | ||
throw transform(error) | ||
} | ||
} | ||
#else | ||
public mutating func next() async throws -> Element? { | ||
clive819 marked this conversation as resolved.
Show resolved
Hide resolved
|
||
do { | ||
return try await base.next() | ||
} catch { | ||
throw transform(error) | ||
} | ||
} | ||
#endif | ||
} | ||
} | ||
|
||
extension AsyncMapErrorSequence: Sendable where Base: Sendable, Base.Element: Sendable {} |
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
Original file line number | Diff line number | Diff line change |
---|---|---|
@@ -0,0 +1,89 @@ | ||
import AsyncAlgorithms | ||
import XCTest | ||
|
||
final class TestMapError: XCTestCase { | ||
|
||
func test_mapError() async throws { | ||
let array = [URLError(.badURL)] | ||
let sequence = array.async | ||
.map { throw $0 } | ||
.mapError { _ in | ||
MyAwesomeError() | ||
} | ||
|
||
do { | ||
for try await _ in sequence { | ||
XCTFail("sequence should throw") | ||
} | ||
} catch { | ||
#if compiler(>=6.0) | ||
// NO-OP | ||
// The compiler already checks that for us since we're using typed throws. | ||
// Writing that assert will just give compiler warning. | ||
clive819 marked this conversation as resolved.
Show resolved
Hide resolved
|
||
#else | ||
XCTAssert(error is MyAwesomeError) | ||
#endif | ||
} | ||
} | ||
|
||
func test_nonThrowing() async throws { | ||
let array = [1, 2, 3, 4, 5] | ||
let sequence = array.async | ||
.mapError { _ in | ||
MyAwesomeError() | ||
} | ||
|
||
var actual: [Int] = [] | ||
for try await value in sequence { | ||
actual.append(value) | ||
} | ||
XCTAssertEqual(array, actual) | ||
} | ||
|
||
func test_cancellation() async throws { | ||
let source = Indefinite(value: "test").async | ||
let sequence = source.mapError { _ in MyAwesomeError() } | ||
|
||
let finished = expectation(description: "finished") | ||
let iterated = expectation(description: "iterated") | ||
|
||
let task = Task { | ||
var firstIteration = false | ||
for try await el in sequence { | ||
XCTAssertEqual(el, "test") | ||
|
||
if !firstIteration { | ||
firstIteration = true | ||
iterated.fulfill() | ||
} | ||
} | ||
finished.fulfill() | ||
} | ||
|
||
// ensure the other task actually starts | ||
await fulfillment(of: [iterated], timeout: 1.0) | ||
// cancellation should ensure the loop finishes | ||
// without regards to the remaining underlying sequence | ||
task.cancel() | ||
await fulfillment(of: [finished], timeout: 1.0) | ||
} | ||
|
||
func test_empty() async throws { | ||
let array: [Int] = [] | ||
let sequence = array.async | ||
.mapError { _ in | ||
MyAwesomeError() | ||
} | ||
|
||
var actual: [Int] = [] | ||
for try await value in sequence { | ||
actual.append(value) | ||
} | ||
XCTAssert(actual.isEmpty) | ||
} | ||
} | ||
|
||
private extension TestMapError { | ||
|
||
struct MyAwesomeError: Error {} | ||
} |
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Uh oh!
There was an error while loading. Please reload this page.