fix Operation.isExecuting (#1080)

Author: weissi

Foundation/Operation.swift

@@ -48,7 +48,13 @@ open class Operation : NSObject {
     }
 
     open func start() {
+        lock.lock()
+        _executing = true
+        lock.unlock()
         main()
+        lock.lock()
+        _executing = false
+        lock.unlock()
         finish()
     }
 
@@ -85,7 +91,12 @@ open class Operation : NSObject {
     }
 
     open var isExecuting: Bool {
-        return _executing
+        let wasExecuting: Bool
+        lock.lock()
+        wasExecuting = _executing
+        lock.unlock()
+
+        return wasExecuting
     }
 
     open var isFinished: Bool {

TestFoundation/TestNSOperationQueue.swift

@@ -23,7 +23,8 @@ class TestNSOperationQueue : XCTestCase {
         return [
             ("test_OperationPriorities", test_OperationPriorities),
             ("test_OperationCount", test_OperationCount),
-            ("test_AsyncOperation", test_AsyncOperation)
+            ("test_AsyncOperation", test_AsyncOperation),
+            ("test_isExecutingWorks", test_isExecutingWorks),
         ]
     }
 
@@ -68,6 +69,26 @@ class TestNSOperationQueue : XCTestCase {
         XCTAssertEqual(msgOperations[3], "Operation4 executed")
     }
 
+    func test_isExecutingWorks() {
+        class _OperationBox {
+            var operation: Operation?
+            init() {
+                self.operation = nil
+            }
+        }
+        let queue = OperationQueue()
+        let opBox = _OperationBox()
+        let op = BlockOperation(block: { XCTAssertEqual(true, opBox.operation?.isExecuting) })
+        opBox.operation = op
+        XCTAssertFalse(op.isExecuting)
+
+        queue.addOperation(op)
+        queue.waitUntilAllOperationsAreFinished()
+        XCTAssertFalse(op.isExecuting)
+
+        opBox.operation = nil /* break the reference cycle op -> <closure> -> opBox -> op */
+    }
+
     func test_AsyncOperation() {
         let operation = AsyncOperation()
         XCTAssertFalse(operation.isExecuting)