Capture filename in partialdiff uri

[Coteh]

Hi, I noticed that when I use the swapdiff VS Code extension to swap two sides of a diff generated with PartialDiff, the filenames in the tab name change.

I believe this is because PartialDiff actually saves the filenames as "text/reg1" and "text/reg2" respectively based on this configuration:

vscode-partial-diff/src/lib/const.ts

Lines 8 to 9 in cda95b9

	REGISTER1: 'reg1',
	REGISTER2: 'reg2',

Here's a couple of screenshots that illustrate my point:

You can see below that the uri for the first PartialDiff file contains just the "reg1" name.

And the swapdiff extension simply does a swap of the two diffs based on visible editor uris:

https://github.com/shalimski/swapdiff/blob/0a5e83288a9c7ef57b663fb55a0a9b0c18323ccf/src/extension.ts#L22

It seems like there's an open VS Code issue at the moment to allow access to the editor tab label via API microsoft/vscode#41909 so I think the best approach is to capture the original filename (edit: and the line number too) within the PartialDiff filename, whether it's an actual file or an "untitled" file, and then other extensions such as swapdiff can make use of those original filenames.

Is this something that's possible to implement? I would be interested in taking a crack at it myself too if possible. :)

[ryu1kn]

@Coteh Thanks for reporting 🙏 Now VSCode seems to natively support diff swap, though that swap button doesn't appear in Partial Diff's diff view (which is just vscode's diff view). I'll see how it can use it and how the diff labels will then look like 👁️

[ryu1kn]

Dug into the VS Code source to understand why the swap button doesn't show up.

The button's visibility is controlled by the activeCompareEditorCanSwap context key, set in editorGroupView.ts.

It requires all of these to be true:

1. The active editor is a DiffEditorInput
2. The original (left) side is not read-only
3. Both sides have a registered FileSystemProvider for their URI scheme (or use the untitled scheme)

Partial Diff fails on (2) and (3):

• Read-only: We use TextDocumentContentProvider, which produces read-only documents by design.
• No FileSystemProvider: The partialdiff scheme is backed by TextDocumentContentProvider, not FileSystemProvider. VS Code's fileService.hasProvider() only checks for FileSystemProvider registrations.

So enabling the native swap button would require migrating from TextDocumentContentProvider to FileSystemProvider — a bigger change than just preserving filenames in URIs. That said, this migration would also unblock other features like editable diffs.