Repository: CodeEditApp/CodeEdit
File: CodeEditModules/Modules/CodeFile/src/CodeFile.swift (Swift)

Code before:
    */
    public var typeOfFile: UTType? {
        if !self.content.isEmpty {
            return UTType.text
        }
        guard let fileType = fileType, let type = UTType(filenameExtension: fileType) else {
            return nil
        }
        if type.conforms(to: UTType.image) {
            return UTType.image
        }
        if type.conforms(to: UTType.text) {
            return UTType.text
        }
        return nil
    }

    /*
     This is the QLPreviewItemURL
     */
    public var previewItemURL: URL {
        guard let fileURL = self.fileURL else {
            return URL(string: "")!
        }
        return fileURL
    }

    // MARK: - NSDocument

    override public class var autosavesInPlace: Bool {
        true
    }

    override public func makeWindowControllers() {
        // Returns the Storyboard that contains your Document window.
        let contentView = CodeFileView(codeFile: self)
        let window = NSWindow(
            contentRect: NSRect(x: 0, y: 0, width: 1400, height: 600),
            styleMask: [.titled, .closable, .miniaturizable, .resizable, .fullSizeContentView],
            backing: .buffered, defer: false
        )
        window.center()
        window.contentView = NSHostingView(rootView: contentView)
        let windowController = NSWindowController(window: window)
        addWindowController(windowController)
    }

    override public func data(ofType _: String) throws -> Data {
        guard let data = content.data(using: .utf8) else { throw CodeFileError.failedToEncode }
        return data
    }

Review comment (bug):
I believe that `URL(string: "")` will return `nil`, so force unwrapping in line 57 will produce a crash. I would suggest changing the `URL` type of this property to `URL?`. 
```suggestion
    public var previewItemURL: URL? {
        fileURL
    }
```
After this change, probably `OtherFileView` also will require changes. IMO presenting an empty view could be a better way than crashing. To achieve that we can change `makeNSView(context:)` method to something like this:
```diff
public func makeNSView(context: Context) -> QLPreviewView {
    let qlPreviewView = QLPreviewView()
-   qlPreviewView.previewItem = otherFile.previewItemURL as QLPreviewItem
+   if let previewItemURL = otherFile.previewItemURL {
+       qlPreviewView.previewItem = previewItemURL as QLPreviewItem
+   }
    return qlPreviewView
}
```
and similary `updateNSView(_:)` method:
```diff
public func updateNSView(_ nsView: QLPreviewView, context: Context) {
-    nsView.previewItem = otherFile.previewItemURL as QLPreviewItem
+    if let previewItemURL = otherFile.previewItemURL {
+        nsView.previewItem = previewItemURL as QLPreviewItem
+    }
}
```


Code after:
            return UTType.text
        }
        guard let fileType = fileType, let type = UTType(filenameExtension: fileType) else {
            return nil
        }
        if type.conforms(to: UTType.image) {
            return UTType.image
        }
        if type.conforms(to: UTType.text) {
            return UTType.text
        }
        return nil
    }

    /*
     This is the QLPreviewItemURL
     */
    public var previewItemURL: URL? {
        fileURL
    }

    // MARK: - NSDocument

    override public class var autosavesInPlace: Bool {
        true
    }

    override public func makeWindowControllers() {
        // Returns the Storyboard that contains your Document window.
        let contentView = CodeFileView(codeFile: self)
        let window = NSWindow(
            contentRect: NSRect(x: 0, y: 0, width: 1400, height: 600),
            styleMask: [.titled, .closable, .miniaturizable, .resizable, .fullSizeContentView],
            backing: .buffered, defer: false
        )
        window.center()
        window.contentView = NSHostingView(rootView: contentView)
        let windowController = NSWindowController(window: window)
        addWindowController(windowController)
    }

    override public func data(ofType _: String) throws -> Data {
        guard let data = content.data(using: .utf8) else { throw CodeFileError.failedToEncode }
        return data
    }

    /// This fuction is used for decoding files.
    /// It should not throw error as unsupported files can still be opened by QLPreviewView.
    override public func read(from data: Data, ofType _: String) throws {
        guard let content = String(data: data, encoding: .utf8) else { return }
        self.content = content