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[Async Refactoring] Wrap code in a continuation if conversion doesn't yield reasonable results

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If we are requested to convert a function to async, but the call in the function’s body that eventually calls the completion handler doesn’t have an async alternative, we are currently copying the call as-is, replacing any calls to the completion handler by placeholders.

For example,
```swift
func testDispatch(completionHandler: @escaping (Int) -> Void) {
  DispatchQueue.global.async {
     completionHandler(longSyncFunc())
  }
}
```
becomes
```swift
func testDispatch() async -> Int  {
  DispatchQueue.global.async {
     <#completionHandler#>(longSyncFunc())
  }
}
```

and

```swift
func testUrlSession(completionHandler: @escaping (Data) -> Void) {
  let task = URLSession.shared.dataTask(with: request) { data, response, error in
    completion(data!)
  }
  task.resume()
}
```
becomes
```swift
func testUrlSession() async -> Data {
  let task = URLSession.shared.dataTask(with: request) { data, response, error in
    <#completion#>(data!)
  }
  task.resume()
}
```

Both of these are better modelled using continuations. Thus, if we find an expression that contains a call to the completion handler and can’t be hoisted to an await statement, we are wrapping the rest of the current scope in a `withChecked(Throwing)Continuation`, producing the following results:

```swift
func testDispatch() async -> Int {
  return await withCheckedContinuation { (continuation: CheckedContinuation<Int, Never>) in
    DispatchQueue.global.async {
      continuation.resume(returning: syncComputation())
    }
  }
}
```

and

```swift
func testDataTask() async -> Int?
  return await withCheckedContinuation { (continuation: CheckedContinuation<Data, Never>) in
    let task = URLSession.shared.dataTask { data, response, error in
      continuation.resume(returning: data!)
    }
    task.resume()
  }
}
```

I think both are much closer to what the developer is actually expecting.

Resolves rdar://79304583
This commit is contained in:
Alex Hoppen
2021-07-01 15:57:49 +02:00
parent d0472e1b21
commit 54fcc90841
3 changed files with 685 additions and 73 deletions
Download Patch File Download Diff File Expand all files Collapse all files

80
test/refactoring/ConvertAsync/convert_function.swift
View File

@@ -129,8 +129,8 @@ func asyncResNewErr(arg: String, _ completion: (Result<String, Error>) -> Void)
// ASYNC-ERR-NEXT: }
// ASYNC-ERR-NEXT: }
// RUN: %refactor -add-async-alternative -dump-text -source-filename %s -pos=%(line+1):1 | %FileCheck -check-prefix=ASYNC-UNHANDLED %s
func asyncUnhandledCompletion(_ completion: (String) -> Void) {
// RUN: %refactor -add-async-alternative -dump-text -source-filename %s -pos=%(line+1):1 | %FileCheck -check-prefix=CALL-NON-ASYNC-IN-ASYNC %s
func callNonAsyncInAsync(_ completion: (String) -> Void) {
simple { str in
let success = run {
completion(str)
@@ -141,19 +141,21 @@ func asyncUnhandledCompletion(_ completion: (String) -> Void) {
}
}
}
// ASYNC-UNHANDLED: func asyncUnhandledCompletion() async -> String {
// ASYNC-UNHANDLED-NEXT: let str = await simple()
// ASYNC-UNHANDLED-NEXT: let success = run {
// ASYNC-UNHANDLED-NEXT: <#completion#>(str)
// ASYNC-UNHANDLED-NEXT: {{^}} return true{{$}}
// ASYNC-UNHANDLED-NEXT: }
// ASYNC-UNHANDLED-NEXT: if !success {
// ASYNC-UNHANDLED-NEXT: {{^}} return "bad"{{$}}
// ASYNC-UNHANDLED-NEXT: }
// ASYNC-UNHANDLED-NEXT: }
// CALL-NON-ASYNC-IN-ASYNC: func callNonAsyncInAsync() async -> String {
// CALL-NON-ASYNC-IN-ASYNC-NEXT: let str = await simple()
// CALL-NON-ASYNC-IN-ASYNC-NEXT: return await withCheckedContinuation { continuation in
// CALL-NON-ASYNC-IN-ASYNC-NEXT: let success = run {
// CALL-NON-ASYNC-IN-ASYNC-NEXT: continuation.resume(returning: str)
// CALL-NON-ASYNC-IN-ASYNC-NEXT: {{^}} return true{{$}}
// CALL-NON-ASYNC-IN-ASYNC-NEXT: }
// CALL-NON-ASYNC-IN-ASYNC-NEXT: if !success {
// CALL-NON-ASYNC-IN-ASYNC-NEXT: continuation.resume(returning: "bad")
// CALL-NON-ASYNC-IN-ASYNC-NEXT: }
// CALL-NON-ASYNC-IN-ASYNC-NEXT: }
// CALL-NON-ASYNC-IN-ASYNC-NEXT: }
// RUN: %refactor -add-async-alternative -dump-text -source-filename %s -pos=%(line+1):1 | %FileCheck -check-prefix=ASYNC-UNHANDLED-COMMENT %s
func asyncUnhandledCommentedCompletion(_ completion: (String) -> Void) {
// RUN: %refactor -add-async-alternative -dump-text -source-filename %s -pos=%(line+1):1 | %FileCheck -check-prefix=CALL-NON-ASYNC-IN-ASYNC-COMMENT %s
func callNonAsyncInAsyncComment(_ completion: (String) -> Void) {
// a
simple { str in // b
// c
@@ -174,28 +176,30 @@ func asyncUnhandledCommentedCompletion(_ completion: (String) -> Void) {
}
// k
}
// ASYNC-UNHANDLED-COMMENT: func asyncUnhandledCommentedCompletion() async -> String {
// ASYNC-UNHANDLED-COMMENT-NEXT: // a
// ASYNC-UNHANDLED-COMMENT-NEXT: let str = await simple()
// ASYNC-UNHANDLED-COMMENT-NEXT: // b
// ASYNC-UNHANDLED-COMMENT-NEXT: // c
// ASYNC-UNHANDLED-COMMENT-NEXT: let success = run {
// ASYNC-UNHANDLED-COMMENT-NEXT: // d
// ASYNC-UNHANDLED-COMMENT-NEXT: <#completion#>(str)
// ASYNC-UNHANDLED-COMMENT-NEXT: // e
// ASYNC-UNHANDLED-COMMENT-NEXT: {{^}} return true{{$}}
// ASYNC-UNHANDLED-COMMENT-NEXT: // f
// ASYNC-UNHANDLED-COMMENT-NEXT: }
// ASYNC-UNHANDLED-COMMENT-NEXT: // g
// ASYNC-UNHANDLED-COMMENT-NEXT: if !success {
// ASYNC-UNHANDLED-COMMENT-NEXT: // h
// ASYNC-UNHANDLED-COMMENT-NEXT: {{^}} return "bad"{{$}}
// ASYNC-UNHANDLED-COMMENT-NEXT: // i
// ASYNC-UNHANDLED-COMMENT-NEXT: }
// ASYNC-UNHANDLED-COMMENT-NEXT: // j
// ASYNC-UNHANDLED-COMMENT-NEXT: {{ }}
// ASYNC-UNHANDLED-COMMENT-NEXT: // k
// ASYNC-UNHANDLED-COMMENT-NEXT: }
// CALL-NON-ASYNC-IN-ASYNC-COMMENT: func callNonAsyncInAsyncComment() async -> String {
// CALL-NON-ASYNC-IN-ASYNC-COMMENT-NEXT: // a
// CALL-NON-ASYNC-IN-ASYNC-COMMENT-NEXT: let str = await simple()
// CALL-NON-ASYNC-IN-ASYNC-COMMENT-NEXT: // b
// CALL-NON-ASYNC-IN-ASYNC-COMMENT-NEXT: // c
// CALL-NON-ASYNC-IN-ASYNC-COMMENT-NEXT: return await withCheckedContinuation { continuation in
// CALL-NON-ASYNC-IN-ASYNC-COMMENT-NEXT: let success = run {
// CALL-NON-ASYNC-IN-ASYNC-COMMENT-NEXT: // d
// CALL-NON-ASYNC-IN-ASYNC-COMMENT-NEXT: continuation.resume(returning: str)
// CALL-NON-ASYNC-IN-ASYNC-COMMENT-NEXT: // e
// CALL-NON-ASYNC-IN-ASYNC-COMMENT-NEXT: {{^}} return true{{$}}
// CALL-NON-ASYNC-IN-ASYNC-COMMENT-NEXT: // f
// CALL-NON-ASYNC-IN-ASYNC-COMMENT-NEXT: }
// CALL-NON-ASYNC-IN-ASYNC-COMMENT-NEXT: // g
// CALL-NON-ASYNC-IN-ASYNC-COMMENT-NEXT: if !success {
// CALL-NON-ASYNC-IN-ASYNC-COMMENT-NEXT: // h
// CALL-NON-ASYNC-IN-ASYNC-COMMENT-NEXT: continuation.resume(returning: "bad")
// CALL-NON-ASYNC-IN-ASYNC-COMMENT-NEXT: // i
// CALL-NON-ASYNC-IN-ASYNC-COMMENT-NEXT: }
// CALL-NON-ASYNC-IN-ASYNC-COMMENT-NEXT: // j
// CALL-NON-ASYNC-IN-ASYNC-COMMENT-NEXT: {{ }}
// CALL-NON-ASYNC-IN-ASYNC-COMMENT-NEXT: // k
// CALL-NON-ASYNC-IN-ASYNC-COMMENT-NEXT: }
// CALL-NON-ASYNC-IN-ASYNC-COMMENT-NEXT: }
// RUN: %refactor -add-async-alternative -dump-text -source-filename %s -pos=%(line+1):1 | %FileCheck -check-prefix VOID-AND-ERROR-HANDLER %s
func voidAndErrorCompletion(completion: (Void?, Error?) -> Void) {
@@ -289,7 +293,9 @@ func testReturnHandling3(_ completion: (String?, Error?) -> Void) {
return (completion("", nil))
}
// RETURN-HANDLING3: func testReturnHandling3() async throws -> String {
// RETURN-HANDLING3-NEXT: {{^}} return (<#completion#>("", nil)){{$}}
// RETURN-HANDLING3-NEXT: return try await withCheckedThrowingContinuation { continuation in
// RETURN-HANDLING3-NEXT: (continuation.resume(returning: ""))
// RETURN-HANDLING3-NEXT: }
// RETURN-HANDLING3-NEXT: }
// RUN: %refactor -convert-to-async -dump-text -source-filename %s -pos=%(line+1):1 | %FileCheck -check-prefix=RDAR78693050 %s