Is it possible to support tree cursor to goto_previous_sibling?

[HerringtonDarkholme]

Hi tree-sitter community! I'm using tree-sitter to build a command line search app. Thanks for maintaining this awesome library!

I'm writing a method prev_all to extract all sibling nodes before a node. Currently, my implementation requires repeated calls of prev_sibling, link.

I want to optimize this pattern to make full use of tree_cursor but looks like it only supports goto_next_sibling at the moment. Is it possible to support traversing siblings backward?

Thanks

[ahlinc]

It's possible but requires a lot of work on the C level + Rust & Wasm bindings + tests.

[daumantas-kavolis-sensmetry]

https://github.com/daumantas-kavolis-sensmetry/tree-sitter/tree/api-extensions but lacks tests

[HerringtonDarkholme]

WOW, that's fast... Thank @daumantas-kavolis-sensmetry! @ahlinc would you consider review this change? It seems to add more than two methods of prev_siblings though.

[daumantas-kavolis-sensmetry]

I had the changes sitting locally for a while but it may take some time before I can add tests for all the new methods.

[ahlinc]

I'm impressed! And definitely want to test the LookaheadIterator concept by myself.

[daumantas-kavolis-sensmetry]

It would be very useful for language servers and generating error messages, together with bidirectional cursors, and completion suggestions. Lookahead iterator already existed internally but was missing public API though it may need to be renamed to something like SymbolIterator as it iterates through symbols at a specified parse state, I just went with the internal name.

[HerringtonDarkholme]

@daumantas-kavolis-sensmetry may I ask if you want to submit a pull request for this?

[daumantas-kavolis-sensmetry]

Not until I have added tests for the new API methods. C API should be mostly fine from my limited manual testing.

[daumantas-kavolis-sensmetry]

@HerringtonDarkholme #2324 Fixed some issues and added tests, should be all good now.

[HerringtonDarkholme]

OMG it looks fantastic 😍