use scratchpad for IW working copy

[amunger]

• Remove the Interactive file scheme and FS provider as they will now be untitled files
• Use the notebook serializer for the IW to simplify saving as an ipynb
  • save as will save and re-open as an ipynb
• Stop registering the notebook editor for *.interactive to prevent overwriting the interactive contributions
• Use untyped input for editorService.OpenEditor to adopt the editor resolver, rather than creating the editorInput ourselves
  • required for letting the WCS handle backup recovery

[bpasero]

I am not deep in any of the code of this PR, is there something specifically you want me to review here? Otherwise I would yield for Pung.

[amunger]

@bpasero - mostly the change in editor registration and usage of the editor service resolver, though I think I have it pretty figured out. Plus you added the 👀, so I figured you wanted to review

[rebornix]

I wonder if we can have better name to indicate that we only want to register the notebook provider info (for resolving notebook model) but we don't want to register an editor.

[amunger]

Actually @bpasero, there is a remaining issue that I will probably want your review on, but I didn't manage to get it done today:

When closing without hot exit:

• Reverting doesn't drop the IW backup. I think that's because we don't fire onDidChangeDirty for scratchpads (so might end up needing a new event pipeline)
• Saving doesn't save the editor in Editor.SaveAll because it only looks for dirty editors to save. It saves on the working copy instead, which doesn't use the suggested target, and also leaves the old editor tab open.

[bpasero]

@amunger is that something for a follow up issue or blocking this PR? if its not blocking then maybe we can do that in a new issue to get this change rolling?

Reverting doesn't drop the IW backup. I think that's because we don't fire onDidChangeDirty for scratchpads (so might end up needing a new event pipeline)

I think my expectation for a reverted scratchpad is that it disposes because there is no other state to revert to. And when it does, we would drop the backup as well:

vscode/src/vs/workbench/services/workingCopy/common/workingCopyBackupTracker.ts

Lines 122 to 135 in 1eabca5

	private onDidUnregister(workingCopy: IWorkingCopy): void {
	// Remove from content version map
	this.mapWorkingCopyToContentVersion.delete(workingCopy);
	// Check suspended
	if (this.suspended) {
	this.logService.warn(`[backup tracker] suspended, ignoring unregister event`, workingCopy.resource.toString(), workingCopy.typeId);
	return;
	}
	// Discard backup
	this.discardBackup(workingCopy);
	}

Looking at the code, that should already happen today:

vscode/src/vs/workbench/services/workingCopy/common/untitledFileWorkingCopy.ts

Lines 303 to 306 in 1eabca5

	// A reverted untitled file working copy is invalid
	// because it has no actual source on disk to revert to.
	// As such we dispose the model.
	this.dispose();

Saving doesn't save the editor in Editor.SaveAll because it only looks for dirty editors to save.

Maybe we need to add a new option for saveAll to even include scratchpads only for this case because here we know we really need to save all editors, including scratchpads.

[amunger]

it would definitely make sense to put it in a separate change, so I'll follow up with that fix after this is merged