Make EventLoopFuture.wait() unavailable from async #2331
Merged
Conversation
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
Motivation: ELF.wait() waits for a condition variable to become true, which can frequently lead to extremely long waits. This is a bad thing to call on a Swift Concurrency thread, especially as we have ELF.get() which is preferable. Modifications: Make ELF.wait() unavailable from async. Result: Users are encouraged to use the correct primitive.
dnadoba
reviewed
Dec 12, 2022
| /// - returns: The value of the `EventLoopFuture` when it completes. | ||
| /// - throws: The error value of the `EventLoopFuture` if it errors. | ||
| @available(*, noasync, message: "threads can change between suspension points and therefore the thread specific value too") |
There was a problem hiding this comment.
Suggested change
| @available(*, noasync, message: "threads can change between suspension points and therefore the thread specific value too") | |
| @available(*, noasync, message: "threads can change between suspension points and therefore the thread specific value too", renamed: "get()") |
This will produce a fixit that will allow users to easily replace it with .get()
warning: instance method 'wait' is unavailable from asynchronous contexts; threads can change between suspension points and therefore the thread specific value too; this is an error in Swift 6
try future.wait()
^~~~
get
Users still need to add await infront but the compiler will nicely provide a fixit for that too.
error: expression is 'async' but is not marked with 'await'
try future.get()
^~~~~~~~~~~~~~~~
await
I understand that we want to encourage users to use get() but I'm not sure I quite understand the message:
threads can change between suspension points and therefore the thread specific value too
wait() doesn't use any thread specific value and AFAIK it is "safe" to use in an async context (except deadlocks) but is just not performant.
There was a problem hiding this comment.
Yeah that is just an overhang from a previous usage I didn't replace.
|
LGTM :) |
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
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.
Motivation:
ELF.wait() waits for a condition variable to become true, which can frequently lead to extremely long waits. This is a bad thing to call on a Swift Concurrency thread, especially as we have ELF.get() which is preferable.
Modifications:
Make ELF.wait() unavailable from async.
Result:
Users are encouraged to use the correct primitive.