Support batch range formatting

[c-claeys]

With Editor: Format On Save Mode set to modifications, VSCode will sequentially send requests to its rangeFormatting provider(s). It'd be nice if the whole list of ranges could be sent at once instead of sequentially, allowing the formatter to handle this batch as it sees fit. This could be achieved by modifying registerDocumentRangeFormattingEditProvider to take an additional optional metadata parameter that the provider can use to express support for this multiRange mode.

[VSCodeTriageBot]

This feature request is now a candidate for our backlog. The community has 60 days to upvote the issue. If it receives 20 upvotes we will move it to our backlog. If not, we will close it. To learn more about how we handle feature requests, please see our documentation.

Happy Coding!

[c-claeys]

Would the team be open to PR for this change? I'm happy to provide one.

[laurentlb]

To give additional context, we've had user reports like this:

Saving takes 5-15 seconds, and during the wait "Formatting via LSP" (or similar) is spinning in the status bar.
What is most surprising though is that (select whole file, and then "format range") gets it done 10x faster. So the task of formatting alone cannot explain the long delay.

When a file has lots of modified chunks, we see lots of round-trips to the server. Batching the requests can provide a very important performance improvement in some cases.

[VSCodeTriageBot]

This feature request has not yet received the 20 community upvotes it takes to make to our backlog. 10 days to go. To learn more about how we handle feature requests, please see our documentation.

Happy Coding!

[jrieken]

feedback from API sync, have explicit optional function

	export interface DocumentRangeFormattingEditProvider {
		provideDocumentRangeFormattingEdits(document: TextDocument, range: Range, options: FormattingOptions, token: CancellationToken): ProviderResult<TextEdit[]>;
		provideDocumentRangesFormattingEdits?(document: TextDocument, ranges: Range[], options: FormattingOptions, token: CancellationToken): ProviderResult<TextEdit[]>;
	}

[jrieken]

fyi @dbaeumer this is done and LSP adoption is welcome

[dbaeumer]

@c-claeys already provided a PR for LSP. https://insiders.vscode.dev/github/microsoft/vscode-languageserver-node/blob/main/protocol/src/common/protocol.ts#L3515

[jrieken]

To verify:

• make sure DocumentRangeFormattingEditProvider API has a new optional function provideDocumentRangesFormattingEdits and make sure it's properly documented
• (extra) write a dummy extension that implements this and make sure it's called