Creating an untitled paw draw file will not open the paw draw editor

[rchiodo]

• VSCode Version: Version: 1.47.0-insider (user setup)
• OS Version: Windows_NT x64 10.0.19041

Steps to Reproduce:

1. Modify the custom-editor-sample to have a 'create new pawdraw' file.
2. Change extension.ts to have code like so:

import * as vscode from 'vscode';
import * as path from 'path';
import * as os from 'os';
import { CatScratchEditorProvider } from './catScratchEditor';
import { PawDrawEditorProvider } from './pawDrawEditor';

export function activate(context: vscode.ExtensionContext) {
	// Register our custom editor providers
	context.subscriptions.push(CatScratchEditorProvider.register(context));

	if (+vscode.version.match(/1\.(\d+)/)![1] >= 45) {
		context.subscriptions.push(PawDrawEditorProvider.register(context));
	}

	vscode.commands.registerCommand('catCustoms.createnew', newPawDraw);
}

function newPawDraw() {
	const file = path.join(os.tmpdir(), 'test-1.pawdraw');
	const uri = vscode.Uri.file(file);
	const untitled = uri.with({ scheme: 'untitled', path: uri.fsPath });
	vscode.commands.executeCommand('vscode.openWith', untitled, 'catCustoms.pawDraw' );
}

3. Modify the package.json to support the new 'catCustoms.pawDraw' command:

"commands": [
            {
                "command": "catCustoms.createnew",
				"title": "Create new Paw Draw",
				"category": "Paw Draw"
            }
		],

4. Run the extension
5. Attempt to run the command
6. This comes up instead of the paw draw editor:

Does this issue occur when all extensions are disabled?: N/A

Note this might be related to:
#93441

[rebornix]

I am seeing exceptions after running this command

Unable to open 'test-1.pawdraw': No file system provider found for resource 'untitled:/var/folders/j7/py1_06vs0y3bbcdpsn0pd66h0000gn/T/test-1.pawdraw'.

I'm wondering if we should always recommend creating untitled file by #98992 (comment)

[connor4312]

reopening due to -found tag

[mjbvz]

Should be fixed by cf0094f

[mjbvz]

Actually never mind, that was for a different issue.

I think the bug here is that the example extension does not handle untitled files properly. The root problem is that we try using the vscode.fs with an untitled: uri, which is not supported. That limitation probably makes sense considering how fs works, but makes handling untitled custom editors more difficult

[rchiodo]

Creating a new file works, but you can't close it.

When I attempt to close the file this happens:

[rchiodo]

@mjbvz is this a known limitation or should I open a separate bug? You kinda made it sound like untitled files just aren't supported.

[mjbvz]

A separate issue would be best. We haven't focused on support for untitled files, in part be because we're still seeing how people use custom editors. We also need proper apis for creating untitled files in the first place