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Fix OperationQueue scheduling logic to prevent disruption of operation lists #2930

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Merged
merged 1 commit into from
Dec 4, 2020
Merged

Fix OperationQueue scheduling logic to prevent disruption of operation lists #2930

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2 changes: 1 addition & 1 deletion Sources/Foundation/Operation.swift
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Original file line number Diff line number Diff line change
Expand Up @@ -993,7 +993,7 @@ open class OperationQueue : NSObject, ProgressReporting {
// if the cached state is possibly not valid then the isReady value needs to be re-updated
if Operation.__NSOperationState.enqueued == operation._state && operation._fetchCachedIsReady(&retest) {
if let previous = prev?.takeUnretainedValue() {
previous.__nextOperation = next
previous.__nextPriorityOperation = next
} else {
_setFirstPriorityOperation(prio, next)
}
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27 changes: 27 additions & 0 deletions Tests/Foundation/Tests/TestOperationQueue.swift
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Expand Up @@ -34,6 +34,7 @@ class TestOperationQueue : XCTestCase {
("test_CancelWhileSuspended", test_CancelWhileSuspended),
("test_OperationOrder", test_OperationOrder),
("test_OperationOrder2", test_OperationOrder2),
("test_ExecutionOrder", test_ExecutionOrder),
("test_WaitUntilFinished", test_WaitUntilFinished),
("test_OperationWaitUntilFinished", test_OperationWaitUntilFinished),
("test_CustomOperationReady", test_CustomOperationReady),
Expand Down Expand Up @@ -531,6 +532,32 @@ class TestOperationQueue : XCTestCase {
XCTAssertEqual(array, [5, 4, 3, 2, 1])
}

func test_ExecutionOrder() {
let queue = OperationQueue()

let didRunOp1 = expectation(description: "Did run first operation")
let didRunOp1Dependency = expectation(description: "Did run first operation dependency")
let didRunOp2 = expectation(description: "Did run second operation")
var didRunOp1DependencyFirst = false

let op1 = BlockOperation {
didRunOp1.fulfill()
XCTAssertTrue(didRunOp1DependencyFirst, "Dependency should be executed first")
}
let op1Dependency = BlockOperation {
didRunOp1Dependency.fulfill()
didRunOp1DependencyFirst = true
}
op1.addDependency(op1Dependency)
queue.addOperations([op1, op1Dependency], waitUntilFinished: false)

queue.addOperation {
didRunOp2.fulfill()
}

waitForExpectations(timeout: 1.0)
}

func test_WaitUntilFinished() {
let queue1 = OperationQueue()
let queue2 = OperationQueue()
Expand Down