Expose 'reading' API for file system providers

[jrieken]

With #47475 we will finalise the file system provider API. With that the only (reading) client of that API will be VS Code itself. We should also allow extensions to use the API, e.g. read a file/folder that's served via a contributed file system provider.

[lostintangent]

This would be extremely compelling for Live Share, since it would allow extensions to access files even on the “guest” side.

[eamodio]

This would also be very valuable for my new proof-of-concept extension RemoteHub

[smikitky]

If I understand correctly, even with this, will each extension developer still have to write something like this?

async function writeToAnywhere(uri, blob) {
  if (uri.scheme === 'file')
    await require('fs.promise').writeFile(uri.fsPath(), blob);
  else
    await vscode.workspace.getFileSystemProviderByScheme(uri.scheme).write(uri, blob);
}

I'm writing an extension that deals with binary files, and I'd love to see an abstraction layer that works transparently with any URI regardless of the scheme, as suggested in #51528. There is already a Node's fs-based FileSystemProvider, which may be used to achieve this.

[jrieken]

If I understand correctly, even with this, will each extension developer still have to write something like this?

No. The goal is to enable something like this await vscode.workspace.writeFile(uri, blob)