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Fix memory leaks in Promise whenAll #1016

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Merged
designatednerd merged 2 commits into from
Feb 13, 2020
Merged

Fix memory leaks in Promise whenAll #1016

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2da9049
Fix memory leaks in Promise whenAll
AnthonyMDev Feb 13, 2020
73ec450
Added unit test
AnthonyMDev Feb 13, 2020
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7 changes: 6 additions & 1 deletion Sources/Apollo/Promise.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -3,6 +3,7 @@ import Dispatch
func whenAll<Value>(_ promises: [Promise<Value>], notifyOn queue: DispatchQueue = .global()) -> Promise<[Value]> {
return Promise { (fulfill, reject) in
let group = DispatchGroup()
var rejected = false

for promise in promises {
group.enter()
Expand All @@ -11,11 +12,15 @@ func whenAll<Value>(_ promises: [Promise<Value>], notifyOn queue: DispatchQueue
group.leave()
}.catch { error in
reject(error)
rejected = true
group.leave()
}
}

group.notify(queue: queue) {
fulfill(promises.map { $0.result!.value! })
if !rejected {
fulfill(promises.map { $0.result!.value! })
}
}
}
}
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7 changes: 6 additions & 1 deletion Sources/Apollo/ResultOrPromise.swift
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Expand Up @@ -19,6 +19,7 @@ func whenAll<Value>(_ resultsOrPromises: [ResultOrPromise<Value>], notifyOn queu

return .promise(Promise { (fulfill, reject) in
let group = DispatchGroup()
var rejected = false

for resultOrPromise in resultsOrPromises {
group.enter()
Expand All @@ -27,11 +28,15 @@ func whenAll<Value>(_ resultsOrPromises: [ResultOrPromise<Value>], notifyOn queu
group.leave()
}.catch { error in
reject(error)
rejected = true
group.leave()
}
}

group.notify(queue: queue) {
fulfill(resultsOrPromises.map { $0.result!.value! })
if !rejected {
fulfill(resultsOrPromises.map { $0.result!.value! })
}
}
})
}
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30 changes: 30 additions & 0 deletions Tests/ApolloTests/PromiseTests.swift
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Expand Up @@ -249,4 +249,34 @@ class PromiseTests: XCTestCase {

waitForExpectations(timeout: 1)
}

func testWhenAllRejectsWhenAnyOfThePromisesRejectsAsync_doesNotCreateMemoryLeak() throws {
var executeReject: ((Error) -> Void)?

var promises: [Promise<String>] = [Promise(fulfilled: "foo"),
Promise<String> { _, reject in executeReject = reject },
Promise(fulfilled: "bar")]
weak var weakPromise0 = promises[0]
weak var weakPromise1 = promises[1]
weak var weakPromise2 = promises[2]

let expectation = self.expectation(description: "whenAll catch handler invoked")

whenAll(promises).catch { error in
XCTAssert(error is TestError)

expectation.fulfill()
}

promises = []
executeReject?(TestError())
executeReject = nil

waitForExpectations(timeout: 1)

XCTAssertNil(weakPromise0)
XCTAssertNil(weakPromise1)
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@designatednerd designatednerd Feb 13, 2020

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So before this fix, this particular assert would fail, correct?

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@AnthonyMDev AnthonyMDev Feb 13, 2020

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Actually, all three of the asserts were failing. The notify block references the entire array of promises, so all of them are retained.

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@designatednerd designatednerd Feb 13, 2020

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oof, ouch. well this is definitely an improvement.

XCTAssertNil(weakPromise2)
}

}
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