fix: storage instance issue (#118)

Author: liuyang1520

Sources/Amplitude/Utilities/OutputFileStream.swift

@@ -50,14 +50,21 @@ internal class OutputFileStream {
         if fileHandle != nil { return }
         do {
             fileHandle = try FileHandle(forWritingTo: fileURL)
+            if #available(macOS 10.15.4, iOS 13.4, macCatalyst 13.4, tvOS 13.4, watchOS 6.2, *) {
+                _ = try? fileHandle?.seekToEnd()
+            } else if #available(tvOS 13.0, *) {
+                try? fileHandle?.seek(toOffset: .max)
+            } else {
+                fileHandle?.seekToEndOfFile()
+            }
         } catch {
             throw OutputStreamError.unableToOpen(fileURL.path)
         }
     }
 
     func write(_ data: Data) throws {
         guard data.isEmpty == false else { return }
-        if #available(macOS 10.15.4, iOS 13.4, macCatalyst 13.4, tvOS 13.4, watchOS 13.4, *) {
+        if #available(macOS 10.15.4, iOS 13.4, macCatalyst 13.4, tvOS 13.4, watchOS 6.2, *) {
             do {
                 try fileHandle?.write(contentsOf: data)
             } catch {

Tests/AmplitudeTests/Storages/PersistentStorageTests.swift

@@ -50,6 +50,33 @@ final class PersistentStorageTests: XCTestCase {
         persistentStorage.reset()
     }
 
+    func testWriteWithTwoInstances() {
+        let persistentStorage1 = PersistentStorage(storagePrefix: "xxx-instance")
+        try? persistentStorage1.write(
+            key: StorageKey.EVENTS,
+            value: BaseEvent(eventType: "test1")
+        )
+        let persistentStorage2 = PersistentStorage(storagePrefix: "xxx-instance")
+        try? persistentStorage2.write(
+            key: StorageKey.EVENTS,
+            value: BaseEvent(eventType: "test2")
+        )
+        // Only read from second instance, reading from first instance insert the "]" at the wrong cursor.
+        let eventFiles2: [URL]? = persistentStorage2.read(key: StorageKey.EVENTS)
+        XCTAssertEqual(eventFiles2?[0].absoluteString.contains("xxx-instance.events.index"), true)
+        XCTAssertNotEqual(eventFiles2?[0].pathExtension, PersistentStorage.TEMP_FILE_EXTENSION)
+
+        XCTAssertEqual(eventFiles2?.count, 1)
+
+        let eventString2 = persistentStorage2.getEventsString(eventBlock: (eventFiles2?[0])!)
+        let decodedEvents = BaseEvent.fromArrayString(jsonString: eventString2!)
+        XCTAssertEqual(decodedEvents!.count, 2)
+        XCTAssertEqual(decodedEvents![0].eventType, "test1")
+        XCTAssertEqual(decodedEvents![1].eventType, "test2")
+        persistentStorage1.reset()
+        persistentStorage2.reset()
+    }
+
     #if os(macOS)
     func testMacOsStorageDirectorySandboxedWhenAppSandboxDisabled() {
         let persistentStorage = PersistentStorage(storagePrefix: "mac-instance")