Made File.Handle a non-copyable struct in the library to adopt Swift 6.4.

Tests/PlaydateKit/MockPlaydate.swift

@@ -422,6 +422,19 @@ enum Mock {
     private static func installJSON() {
         jsonAPI.initialize(to: playdate_json())
 
+        // Pulls one chunk through the reader, as the OS would, and decodes
+        // it as `null`.
+        jsonAPI.pointee.decode = { _, reader, outval in
+            var buffer = [UInt8](repeating: 0, count: 16)
+            let count = buffer.withUnsafeMutableBufferPointer { buffer in
+                reader.read?(reader.userdata, buffer.baseAddress, Int32(buffer.count)) ?? -1
+            }
+            Mock.record("decode(\(count))")
+            outval?.pointee = json_value()
+            outval?.pointee.type = CChar(kJSONNull.rawValue)
+            return 1
+        }
+
         jsonAPI.pointee.decodeString = { decoder, _, outval in
             guard let decoder else { return 0 }
 

Tests/PlaydateKit/WrapperTests.swift

@@ -345,6 +345,26 @@ struct WrapperTests {
         #expect(Mock.eventCount("close") == 1)
     }
 
+    @Test func jsonDecodeFileReadsThroughTheHandleAndClosesIt() throws {
+        Mock.fileReadLimit = 5
+        let value = try JSON.decodeFile(path: "save.json")
+        guard case .null = value else {
+            Issue.record("expected .null, got \(value)")
+            return
+        }
+        #expect(Mock.events.contains("decode(5)"))
+        #expect(Mock.eventCount("close") == 1)
+    }
+
+    @Test func fileHandleClosesWhenItGoesOutOfScope() throws {
+        do {
+            let handle = try File.Handle(path: "save.dat", mode: .write)
+            _ = try handle.write([1])
+            #expect(Mock.eventCount("close") == 0)
+        }
+        #expect(Mock.eventCount("close") == 1)
+    }
+
     @Test func fileHandleReadLengthReturnsOnlyTheBytesRead() throws {
         let handle = try File.Handle(path: "save.dat", mode: [.read, .readData])