[cross_file_darwin] iOS/macOS implementation of cross_file

[bparrishMines]

Part of flutter/flutter#91869

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[gemini-code-assist]

Code Review

This pull request introduces the cross_file_darwin package, providing a Darwin-specific implementation for the cross_file plugin, including support for security-scoped resources and PhotoKit assets. The implementation uses Pigeon for communication between Dart and native code, along with FFI for native asset resource management. The review identified several critical issues, including a missing delegate assignment in AssetResourceReader, incorrect URI-to-file-path conversions in canRead methods, a missing return statement in lastModified, and inconsistent parameter usage in helper methods within darwin_scoped_storage_cross_file.dart.

[gemini-code-assist]

The delegate parameter passed to openRead is never assigned to self.delegate. As a result, self.delegate remains nil, and the callbacks onDataReceived and onCompletion are never triggered.

  func openRead(localIdentifier: String, delegate: AssetResourceReaderDelegate) -> Bool {
    self.delegate = delegate
    let assets = PHAsset.fetchAssets(withLocalIdentifiers: [localIdentifier], options: nil)

[bparrishMines]

very good catch. This is the down side of not being able to write tests when the api requires out of app user interactions.

[stuartmorgan-g]

LGTM