[Concurrency] Don't lose name information from completion-handler arguments #34394
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…uments. When a completion handler parameter has a selector piece that ends with "WithCompletion(Handler)", prepend the text before that suffix to the base name or previous argument label, as appropriate. This ensures that we don't lose information from the name, particularly with delegate names.
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@swift-ci please smoke test |
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While you're here, would it make sense to add |
FWIW, it doesn't show up in the iOS or macOS SDKs at all, and a general web search finds relatively few uses. |
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| -(void)doSomethingConflicted:(NSString *)operation completionHandler:(void (^)(NSInteger))handler; | |||
| -(NSInteger)doSomethingConflicted:(NSString *)operation; | |||
| -(void)server:(NSString *)name restartWithCompletionHandler:(void (^)(void))block; | |||
| -(void)server:(NSString *)name atPriority:(double)priority restartWithCompletionHandler:(void (^)(void))block; | |||
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Suggestion: I'm not sure what real-life APIs you're looking at, but at least rationalizing based on this example, it may make the most sense to translate these APIs by prepending the information to the base name at all times: await is really taking the place of the completion handler, and it lives on the opposite side of the expression as compared to a trailing closure.
server:atPriority:restartWithCompletionHandler:
// ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ trailing closures are ergonomic
await server.server("localhost", atPriorityRestart: 0.8)
// ^^^^^ ^^^^^^^ await ... wait for it ... restart
If the Objective-C importer were to translate these names by first logically shuffling this information to the front, then it seems to me like it'd be a consistently better result:
// Original
thing:frobnicateWithCompletionHandler:
// Rearrange to pull name information next to `await` use site
frobnicateWithCompletionHandler:thing:
// Eliminate "WithCompletionHandler"
frobnicateThing:
When the design for async/await is eventually shared, I hope you'll devote some text to translation from legacy APIs for discussion and possible enhancement, just like the review process that the original Objective-C-to-Swift translation went through.
When a completion handler parameter has a selector piece that ends with
"WithCompletion(Handler)", prepend the text before that suffix to the
base name or previous argument label, as appropriate. This ensures that
we don't lose information from the name, particularly with delegate names.