fs module should support writing from Blob and web ReadableStream sources

What is the problem this feature will solve?

Currently, all Node.js fs module methods for writing data (such as fs.write, fs.createWriteStream) only accept Buffers or strings. There is no built-in support for writing data directly from Blob or web ReadableStream sources. This limits interoperability with web platform APIs and makes working with large files or streaming data @less seamless, especially when trying to move data efficiently from web contexts into the filesystem. Furthermore, Node.js provides fs.readableWebStream, but no corresponding fs.createWritableStream that would allow writing from web streams or Blobs directly.

What is the feature you are proposing to solve the problem?

Extend the Node.js fs module with the following capabilities:

• Allow fs.write and related write methods to accept Blob objects as a valid input, making it possible to write the entirety of a Blob's contents to a file without manual conversion to Buffer.
• Introduce fs.createWritableStream (web-compatible), which would be a direct counterpart to fs.readableWebStream and support writing from web ReadableStream sources to files.

This would improve ease-of-use when working with large binary/web platform data and make fs more aligned with modern web standards.

What alternatives have you considered?

Current workarounds involve manually converting Blobs and web streams into Buffers or converting web streams into node:streams

The only solution we have today is to use the fs.promise.writeFile(path, webStream) which luckily supports async iterable

able to write Blob's would enable efficient native copy operations (like using openAsBlob(path) and writing directly to another file) without data passing through the JS runtime.

able to write blobs avoids extra conversions/allocations in JS, reduces memory footprint and GC pressure

the solution i'm looking for is something like:

blob = new Blob(['hello world'])
await filehandle.write(blob)

await blob.stream().pipeTo(fs.createWritableStream(dest))

// using fetch is becoming more popular, so a web writable stream is highly requested
await new Response('...').body.pipeTo(fs.createWritableStream(dest))

Read the existing fs.write, fs.promises.writeFile, fs.readableWebStream, and filehandle.appendFile behavior first, then compare it with the Blob and web ReadableStream cases in the issue. Done means the supported scope is agreed and the requested write APIs handle the stated Blob and web-stream use cases.