Copy binary files for each target in FileSystemPublisher.initFiles() #63

Summary

• Goal: FileSystemPublisher.initFiles(files, binaryFiles) delivers binary files to every target and keeps the caller's buffers usable, like writeFile().
• Current gap: initFiles() passes the same transfer list, which holds the caller's ArrayBuffers, to the postMessage() of every target.
  • The first call transfers the buffers, which detaches them.
  • With two or more targets, the next call therefore throws a DataCloneError.
  • With one target, the caller's buffers end up detached.
• Effect:
  • With two targets, such as a Web Worker and a Service Worker, initFiles() throws after only the first target has received the files.
  • With any number of targets, the caller loses its ArrayBuffers.
• Request: Copy each binary file for each target, as writeFile() does since #61.
• Verification status: Reproduced in Node.js v24.21.0 with MessageChannel ports and the built package (see Details). Not checked in a browser. Transferring a detached ArrayBuffer throws a DataCloneError there as well.
• Related: Found while implementing #42, which fixed the same problem in writeFile(). Vrowzer itself does not call initFiles(), but @vrowzer/fs/watcher exports it.

Details

const first = new MessageChannel()
const second = new MessageChannel()
const publisher = createFileSystemPublisher([first.port1, second.port1])
const buffer = new Uint8Array([1, 2, 3]).buffer

publisher.initFiles(undefined, { '/a.bin': buffer })
// throws DataCloneError: Cannot transfer object of unsupported type.
buffer.byteLength // 0

const single = new MessageChannel()
const other = new Uint8Array([4, 5]).buffer
createFileSystemPublisher([single.port1]).initFiles(undefined, { '/b.bin': other })
other.byteLength // 0