SR-13822: FileHandle closeOnDealloc is not respected

Author: spevans

Sources/Foundation/FileHandle.swift

@@ -477,7 +477,9 @@ open class FileHandle : NSObject {
         // - deinit tries to .sync { … } to serialize the work on the handle queue, _which we're already on_
         // - deadlock! DispatchQueue's deadlock detection triggers and crashes us.
         // since all operations on the handle queue retain the handle during use, if the handle is being deinited, then there are no more operations on the queue, so this is serial with respect to them anyway. Just close the handle immediately.
-        try? _immediatelyClose()
+        if _closeOnDealloc {
+            try? _immediatelyClose()
+        }
     }
 
     // MARK: -

Tests/Foundation/Tests/TestFileHandle.swift

@@ -579,7 +579,40 @@ class TestFileHandle : XCTestCase {
             XCTAssertTrue(notificationReceived, "Notification should be sent")
         }
     }
-    
+
+#if NS_FOUNDATION_ALLOWS_TESTABLE_IMPORT
+    func test_closeOnDealloc() throws {
+        try withTemporaryDirectory() { (url, path) in
+            let data = try XCTUnwrap("hello".data(using: .utf8))
+
+            // closeOnDealloc: true, 2nd write should throw.
+            do {
+                let fileUrl = url.appendingPathComponent("testfile")
+                let fd = try FileHandle._openFileDescriptorForURL(fileUrl, flags: O_CREAT | O_RDWR, reading: false)
+                do {
+                    let fh = FileHandle(fileDescriptor: fd, closeOnDealloc: true)
+                    XCTAssertNoThrow(try fh.write(contentsOf: data))
+                }
+                let fh2 = FileHandle(fileDescriptor: fd, closeOnDealloc: true)
+                XCTAssertThrowsError(try fh2.write(contentsOf: data))
+            }
+
+            // closeOnDealloc: false, 2nd write shoud succeed.
+            do {
+                let fileUrl = url.appendingPathComponent("testfile2")
+                let fd = try FileHandle._openFileDescriptorForURL(fileUrl, flags: O_CREAT | O_RDWR, reading: false)
+                do {
+                    let fh = FileHandle(fileDescriptor: fd, closeOnDealloc: false)
+                    XCTAssertNoThrow(try fh.write(contentsOf: data))
+                }
+                // Close the file handle after this write, dont leave it open after this test.
+                let fh2 = FileHandle(fileDescriptor: fd, closeOnDealloc: true)
+                XCTAssertNoThrow(try fh2.write(contentsOf: data))
+            }
+        }
+    }
+#endif
+
     static var allTests : [(String, (TestFileHandle) -> () throws -> ())] {
         var tests: [(String, (TestFileHandle) -> () throws -> ())] = [
             ("testReadUpToCount", testReadUpToCount),
@@ -607,6 +640,7 @@ class TestFileHandle : XCTestCase {
             ("test_nullDevice", test_nullDevice),
             ("testHandleCreationAndCleanup", testHandleCreationAndCleanup),
             ("testOffset", testOffset),
+            ("test_closeOnDealloc", test_closeOnDealloc),
         ])
 #endif