fix(folds): update fold boundaries after headline edits (#1078)

* fix(foldtext): invalidate cache on buffer changes

The foldtext highlight cache was keyed by line number but never
invalidated when buffer content changed. After edits that insert
or remove lines, cached entries mapped to wrong content.

Track changedtick per buffer and clear the cache in on_win when
it changes. This is checked once per window per redraw cycle.

* fix(folds): update boundaries after edits

Neovim's treesitter foldexpr only re-evaluates fold levels for
lines reported in on_changedtree, which typically covers just the
edited headline. But fold boundaries extend to the end of the
section, so they go stale after TODO, priority or tag changes.

Capture the section range before the edit (TS nodes become stale
after buffer changes), then schedule vim._foldupdate for the full
section range after treesitter has reparsed.

Author: seflue

lua/orgmode/colors/highlighter/foldtext.lua

@@ -6,19 +6,32 @@ local config = require('orgmode.config')
 ---@field highlighter OrgHighlighter
 ---@field namespace number
 ---@field cache table<number, table<number, OrgFoldtextLineValue>>
+---@field cache_tick table<number, number>
 local OrgFoldtext = {}
 
 ---@param opts { highlighter: OrgHighlighter }
 function OrgFoldtext:new(opts)
   local data = {
     highlighter = opts.highlighter,
     cache = setmetatable({}, { __mode = 'k' }),
+    cache_tick = {},
   }
   setmetatable(data, self)
   self.__index = self
   return data
 end
 
+---Invalidate cache for a buffer if its content has changed since the last render.
+---Call this once per redraw from on_win, not per line.
+---@param bufnr number
+function OrgFoldtext:check_cache(bufnr)
+  local tick = vim.api.nvim_buf_get_changedtick(bufnr)
+  if self.cache_tick[bufnr] ~= tick then
+    self.cache[bufnr] = nil
+    self.cache_tick[bufnr] = tick
+  end
+end
+
 ---@param bufnr number
 ---@param line number
 ---@param value OrgFoldtextLineValue
@@ -101,6 +114,7 @@ end
 
 function OrgFoldtext:on_detach(bufnr)
   self.cache[bufnr] = nil
+  self.cache_tick[bufnr] = nil
 end
 
 return OrgFoldtext

lua/orgmode/colors/highlighter/init.lua

@@ -78,6 +78,7 @@ function OrgHighlighter:_on_win(_, win, bufnr, topline, botline)
       end,
     })
   else
+    self.foldtext:check_cache(bufnr)
     self:_parse_tree(bufnr, win, { topline, botline + 1 })
     if self.parsing[win] then
       for line = topline, botline do

lua/orgmode/org/mappings.lua

@@ -17,6 +17,25 @@ local Promise = require('orgmode.utils.promise')
 local Input = require('orgmode.ui.input')
 local Footnote = require('orgmode.objects.footnote')
 
+---Schedule a fold update for the given range. Call after buffer edits.
+---OrgRange is 1-indexed; vim._foldupdate expects 0-indexed lines.
+---@param range OrgRange
+local function schedule_fold_update(range)
+  local bufnr = vim.api.nvim_get_current_buf()
+  vim.schedule(function()
+    if not vim.api.nvim_buf_is_valid(bufnr) then
+      return
+    end
+    local start_line = range.start_line - 1
+    local end_line = math.min(range.end_line, vim.api.nvim_buf_line_count(bufnr))
+    for _, win in ipairs(vim.fn.win_findbuf(bufnr)) do
+      if vim.wo[win].foldmethod == 'expr' then
+        vim._foldupdate(win, start_line, end_line)
+      end
+    end
+  end)
+end
+
 ---@class OrgMappings
 ---@field capture OrgCapture
 ---@field agenda OrgAgenda
@@ -50,6 +69,8 @@ function OrgMappings:set_tags(tags)
   local headline = self.files:get_closest_headline()
   local headline_tags = headline:get_own_tags()
   local current_tags = utils.tags_to_string(headline_tags)
+  -- Capture range before promise chain — TS nodes become stale after edits
+  local range = headline:get_range()
 
   return Promise.resolve()
     :next(function()
@@ -69,14 +90,17 @@ function OrgMappings:set_tags(tags)
         return
       end
 
-      return headline:set_tags(new_tags)
+      headline:set_tags(new_tags)
+      schedule_fold_update(range)
     end)
 end
 
 ---@return nil
 function OrgMappings:toggle_archive_tag()
   local headline = self.files:get_closest_headline()
+  local range = headline:get_range()
   headline:toggle_tag('ARCHIVE')
+  schedule_fold_update(range)
 end
 
 function OrgMappings:cycle()
@@ -344,7 +368,9 @@ function OrgMappings:set_priority(direction)
     end
   end
 
+  local range = headline:get_range()
   headline:set_priority(new_priority)
+  schedule_fold_update(range)
 end
 
 function OrgMappings:todo_next_state()
@@ -419,6 +445,9 @@ function OrgMappings:_todo_change_state(direction)
   local headline = self.files:get_closest_headline()
   local old_state = headline:get_todo()
   local was_done = headline:is_done()
+
+  local range = headline:get_range()
+
   local changed = self:_change_todo_state(direction, true)
 
   if not changed then
@@ -428,6 +457,8 @@ function OrgMappings:_todo_change_state(direction)
   local item = self.files:get_closest_headline()
   EventManager.dispatch(events.TodoChanged:new(item, old_state, was_done))
 
+  schedule_fold_update(range)
+
   local is_done = item:is_done() and not was_done
   local is_undone = not item:is_done() and was_done