fix(files): handle stale treesitter nodes gracefully

[seflue]

Summary

This PR fixes intermittent "Index out of bounds" errors when treesitter nodes become stale after buffer modifications.

The error occurs when:

1. Buffer is parsed, nodes are cached
2. Buffer content changes (user edits)
3. Cached nodes are accessed via async callback (e.g., vim.schedule)
4. Node positions now point to invalid ranges → crash

Example error:

Error executing vim.schedule lua callback: .../treesitter.lua:195: Index out of bounds
stack traceback:
        [C]: in function 'nvim_buf_get_text'
        .../treesitter.lua:195: in function 'get_node_text'
        .../orgmode/files/headline.lua:545: in function 'get_property'

Related Issues

Changes

• Wrap get_node_text() in pcall to gracefully handle stale nodes
• Return empty string on failure instead of crashing
• Add _parse_tick field to track buffer state at parse time
• Add OrgFile:is_tree_stale() for callers that need explicit staleness checks

Checklist

I confirm that I have:

• Followed the Conventional Commits specification (e.g., feat: add new feature, fix: correct bug, docs: update documentation).
• My PR title also follows the conventional commits specification.
• Updated relevant documentation, if necessary.
• Thoroughly tested my changes.
• Added tests (if applicable) and verified existing tests pass with make test.
• Checked for breaking changes and documented them, if any.

[kristijanhusak]

Thanks for the PR! It seems unfinished though.

[kristijanhusak]

Do you know how can I reproduce this? Cache should revalidate when node changes, and I'm curious if we could handle it differently.

[kristijanhusak]

Thanks for the PR, and sorry for the delay.
I left a comment on the logic, we can simplify it a bit.

[kristijanhusak]

No need to parse here, the method that is being called should do the parsing when it's really called. We just need to make sure that the cache is invalidated. We can append the changedtick to the id, and that does the trick. This works for me:

local memoize = Memoize:new(OrgFile, function(self)
  local tick = 0
  local bufnr = self:bufnr()
  if bufnr and bufnr > -1 then
    tick = vim.api.nvim_buf_get_changedtick(bufnr)
  end
  return {
    file = self,
    id = table.concat({ 'file', self.root and self.root:id() or '', tick }, '_'),
  }
end)

We also don't need to track the _parse_tick any more.