formatter: support `TextEdit` LSP struct

[Sysix]

Starting on working to implement oxfmt into the language server, the first problem I found is that the service of oxfmt will check if the complete source code is changed and modifies it

oxc/apps/oxfmt/src/service.rs

Lines 67 to 70 in 78a1146

	let code = Formatter::new(&allocator, options).build(&ret.program);
	let elapsed = start_time.elapsed();
	let is_changed = source_text != code;

The Language Server Protocol supports formatting too, but tells the client what to change.
This happens normally with Range/Span and the new source text:
https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#textDocument_formatting

Feature request:

Implement a logic, so the server can send the partial source text, which should be modified, to the client.

Response:
result: TextEdit[] | null describing the modification to the document to be formatted.
error: code and message set in case an exception happens during the formatting request.

Other solution:

Just send the complete text file. Do not know how this will result into text cursor position and maybe other problems.

[leaysgur]

Thank you as always!

Let me just confirm my understanding.

There are 3 cases to be implemented for fully supporting LSP.

• textDocument/formatting
• textDocument/rangeFormatting
• textDocument/onTypeFormatting

And initially, we planned to implement only full-text formatting.

We are aware that there is currently no mechanism to keep the cursor position, and it is necessary.
(However, due to priority, it seems that work on it will start a little later.)

In this case, would it be fine to implement something like service::run_single() for LSP instead of using oxfmt/src/service::run()(for CLI)?

[camc314]

We are aware that there is currently no mechanism to keep the cursor position, and it is necessary.

I mentioned this last week. But due to the way the lsp protocol works, we actually don't have to care about this. When the editor asks us to format a text document, it asks us to return Result<Option<Vec<TextEdit>>>, which is effectivly the diff between the current text doc and the new text document. This means that the editor can correctly position the cursor based on these edits.

[leaysgur]

Thanks for the follow-up! It's really helpful.

I had convinced myself it was necessary because I knew there was a lot of code in Prettier's codebase that handled cursors. e.g. prettier.formatWithCursor() 😓

Then, it seems we should format the entire text and just implement minimalEdit in our LSP.

[Sysix]

In this case, would it be fine to implement something like service::run_single() for LSP instead of using oxfmt/src/service::run()(for CLI)?

I guess this will be the goal, we did the same inside linter::Runtime

Then, it seems we should format the entire text and just implement minimalEdit in our LSP.

I did not look how prettier done it :) Thanks for the link. This will be a good start 🥳
Do not know if the overhead of comparing both source texts (old and one) is fine for the long run.
I hoped for some functionality like the linter does it with the fix for CLI and LSP (see linter::Runtime again )