How to work with FileSystemProvider file systems in Visual Studio Code - visual-studio-code

Question

I've noticed the new FileSystemProvider API which looks great, but it seems that there is an expectation for plugins to be able to handle files within any custom file system created using this interface.
I've tried using node’s built in fs, which won't work, because the path within a Uri doesn't relate to the filesystem on the host machine, but to the arbitrary filesystem defined in another extension.
I've also tried the following (with the test memfs extension in use):
let uri = new vscode.Uri('memfs', '', fileName);
let fsp = new vscode.FileSystemProvider();
fsp.writeFile(uri)
.then(() => {
console.log('written file');
});
But it doesn't seem that FileSystemProvider exposes itself in the way I was expecting.
How, if at all, can a plugin make use of and perform file operations on URIs which are in the custom schemes that these arbitrary file systems can possess?

Answer 1

I ran into the same problem. It turns out FileSystemProvider is an interface that a provider should implement.
There is a great sample from Microsoft on GitHub.
The crux of it is this:
First, they create a new class called MemFS, which implements vscode.FileSystemProvider.
Then they register it like this:
const memFs = new MemFS();
context.subscriptions.push(
vscode.workspace.registerFileSystemProvider('memfs', memFs, {
isCaseSensitive: true
}));
The first parameter to registerFileSystemProvider is the scheme, which means that file system provider will be used whenever you use a URI starting with memfs://.
So you use fs as normal, and the scheme determines the FileSystemProvider that will actually be used. This is great, because it really makes it transparent to you whether the file being manipulated is on the disk, some server on the other side of the world, or dynamically generated by the provider.