"Workspace folder was undefined" message in Tasks Output channel when new workspace uses FileSystemProvider

[gjsjohnmurray]

Type: Bug

1. Install https://marketplace.visualstudio.com/items?itemName=jrieken.vscode-memfs from Marketplace which is a packaged version of fsprovider-sample
2. Open Panel, switch to Output tab and choose Tasks channel.
3. With no folder or workspace open, run the MemFS: Setup Workspace command.
4. Observe the "Workspace folder was undefined" message.

The message come from here:

vscode/src/vs/workbench/contrib/tasks/browser/abstractTaskService.ts

Line 2373 in 6de0c23

problemReporter.fatal(nls.localize('TaskSystem.workspaceFolderError', 'Workspace folder was undefined'));

I think the task system is trying to do something (an onFolderOpen task?) for the memfs scheme before the task system for that scheme has been registered.

As a minimum change I think the message should become "Task system for ${workspaceFolder.uri.scheme} is unavailable".

Better, the message could be suppressed.

Best, the sequencing could be revised so the task system registration for the FSP's scheme happens before it is first used.

Further observation is that running Developer: Reload Window does not produce the message again.

VS Code version: Code 1.82.0 (8b617bd, 2023-09-06T22:07:07.438Z)
OS version: Windows_NT x64 10.0.22621
Modes:

[gjsjohnmurray]

Note, this is not a new 1.82 problem. It also happened in 1.81.1.

[gjsjohnmurray]

I started looking at fixing this, but didn't find a path that calls registerTaskSystem for any schemes other than Schemas.vscodeRemote and Schemas.file.

Should it also be getting called for schemes that FileSystemProviders implement?

[gjsjohnmurray]

The "Workspace folder was undefined" message was introduced by #168209

Pinging @meganrogge and @alexr00 about what should happen for a scheme contributed by a FSP.

[gjsjohnmurray]

Pinging @meganrogge and @alexr00 about what should happen for a scheme contributed by a FSP.

Scratch that - I believe I have answered my own question in the PR I just submitted.