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Konrad Malawski
bfe8dbca59
Pending swift evolution discussion: https://github.com/swiftlang/swift-evolution/pull/3133 replaces #87171 update new error message according to proposal also handle untyped throws in _nonDiscardableWhenThrowing attr Rename the internal attr _nonDiscardableWhenThrowingOperation
49 lines
1.4 KiB
Markdown
49 lines
1.4 KiB
Markdown
# Unused throwing unstructured task creation (NoUseUnstructuredThrowingTask)
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## Overview
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Creating a throwing unstructured `Task` without storing or discarding its result means any error thrown
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by the task body will be silently ignored. Resolve this warning by explicitly storing or discarding the
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task reference.
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For example:
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```swift
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func example() {
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Task { throw MyError() }
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}
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```
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Building this code produces a warning about the unused unstructured task:
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```
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| func example() {
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| Task { throw MyError() }
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| `- warning: unstructured throwing task created by 'init(name:priority:operation:)' is not used, which may accidentally ignore errors thrown inside the task
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| note: to silence this warning, handle the error inside the task, or store/discard the task value explicitly
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| }
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```
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By storing the task reference and awaiting it, you won't miss the error thrown by the task operation because awaiting `task.value` will be forced to acknowledge the thrown error with `try`:
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```swift
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let task = Task { throw MyError() }
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try await task.value
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```
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Alternatively, ignore the thrown error explicitly:
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```swift
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_ = Task { throw MyError() }
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```
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### Cancelling unstructured tasks
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Another reason to keep references to unstructured tasks is to be able to cancel them explicitly:
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```swift
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let task = Task { try Task.sleep(for: .seconds(10)) }
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task.cancel() // cancel and wake-up the sleeping task
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try await task.value
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```
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