[BUG] [iOS] Unserializable objects in downloadFile call argument cause download failing

[AceOfWands]

Bug Report

Plugin(s)

• @capacitor/filesystem: 6.0.2

Capacitor Version

💊   Capacitor Doctor  💊 

Latest Dependencies:

  @capacitor/cli: 6.2.0
  @capacitor/core: 6.2.0
  @capacitor/android: 6.2.0
  @capacitor/ios: 6.2.0

Installed Dependencies:

  @capacitor/cli: 6.1.2
  @capacitor/core: 6.1.2
  @capacitor/android: 6.1.2
  @capacitor/ios: 6.1.2

[success] iOS looking great! 👌
[success] Android looking great! 👌

Platform(s)

• iOS

Current Behavior

When running the app on iOS, adding a webFetchExtra property containing an abort controller signal to the argument passed to the downloadFile method causes a DataCloneError exception to be thrown, resulting in the download failing.

Here is the problematic code snippet:

await Filesystem.downloadFile({
  path: path,
  url: downloadUrl,
  directory: directory,
  progress: true,
  webFetchExtra: { signal },
  readTimeout: 7000,
});

Expected Behavior

The downloadFile method should not throw a DataCloneError. Either:

• The argument passed to the downloadFile method should be fully serialized before being pushed to the web worker, or
• The webFetchExtra property should be removed entirely before the data is sent to native platforms if it's not used there.

Code Reproduction

Reproduce the issue by using the following code:

const controller = new AbortController();
const signal = controller.signal;
await Filesystem.downloadFile({
  path: "Download/logo.png",
  url: "https://upload.wikimedia.org/wikipedia/commons/thumb/8/80/Wikipedia-logo-v2.svg/1200px-Wikipedia-logo-v2.svg.png",
  directory: Directory.ExternalStorage,
  webFetchExtra: { signal }
});

Other Technical Details

• Error: DataCloneError
• Cause: The signal object is not serializable but is still pushed to the web worker.
• Notes: The error occurs because signal (part of AbortController) cannot be cloned or serialized for transfer between threads.

Additional Context

The downloadFile argument must either be fully serialized or have its webFetchExtra property stripped out before being sent to the native layer.

[Ionitron]

This issue needs more information before it can be addressed.
In particular, the reporter needs to provide a minimal sample app that demonstrates the issue.
If no sample app is provided within 15 days, the issue will be closed.

Please see the Contributing Guide for how to create a Sample App.

Thanks!
Ionitron 💙