feat(treesitter): table of contents for checkhealth, markdown (#32282)

Problem: It's difficult to navigate large structured text files (vim
help, checkhealth, Markdown).

Solution: Support `gO` for table of contents and `]]`/`[[` for moving
between headings for all these filetypes using treesitter queries.

Refactor: colorization of highlight groups is moved to the `help` ftplugin
while headings-related functionality is implemented in a private
`vim.treesitter` module for possible future use for other filetypes.

1 files changed, 0 insertions, 71 deletions

diff --git a/runtime/lua/vim/vimhelp.lua b/runtime/lua/vim/vimhelp.lua
deleted file mode 100644
index a494d311b1..0000000000
--- a/runtime/lua/vim/vimhelp.lua
+++ /dev/null
@@ -1,71 +0,0 @@
--- Extra functionality for displaying Vim help.
-
-local M = {}
-
---- Apply current colorscheme to lists of default highlight groups
----
---- Note: {patterns} is assumed to be sorted by occurrence in the file.
---- @param patterns {start:string,stop:string,match:string}[]
-function M.highlight_groups(patterns)
-  local ns = vim.api.nvim_create_namespace('nvim.vimhelp')
-  vim.api.nvim_buf_clear_namespace(0, ns, 0, -1)
-
-  local save_cursor = vim.fn.getcurpos()
-
-  for _, pat in pairs(patterns) do
-    local start_lnum = vim.fn.search(pat.start, 'c')
-    local end_lnum = vim.fn.search(pat.stop)
-    if start_lnum == 0 or end_lnum == 0 then
-      break
-    end
-
-    for lnum = start_lnum, end_lnum do
-      local word = vim.api.nvim_buf_get_lines(0, lnum - 1, lnum, true)[1]:match(pat.match)
-      if vim.fn.hlexists(word) ~= 0 then
-        vim.api.nvim_buf_set_extmark(0, ns, lnum - 1, 0, { end_col = #word, hl_group = word })
-      end
-    end
-  end
-
-  vim.fn.setpos('.', save_cursor)
-end
-
---- Show a table of contents for the help buffer in a loclist
-function M.show_toc()
-  local bufnr = vim.api.nvim_get_current_buf()
-  local parser = assert(vim.treesitter.get_parser(bufnr, 'vimdoc', { error = false }))
-  local query = vim.treesitter.query.parse(
-    parser:lang(),
-    [[
-    (h1 (heading) @h1)
-    (h2 (heading) @h2)
-    (h3 (heading) @h3)
-    (column_heading (heading) @h4)
-  ]]
-  )
-  local root = parser:parse()[1]:root()
-  local headings = {}
-  for id, node, _, _ in query:iter_captures(root, bufnr) do
-    local text = vim.treesitter.get_node_text(node, bufnr)
-    local capture = query.captures[id]
-    local row, col = node:start()
-    -- only column_headings at col 1 are headings, otherwise it's code examples
-    local is_code = (capture == 'h4' and col > 0)
-    -- ignore tabular material
-    local is_table = (capture == 'h4' and (text:find('\t') or text:find('  ')))
-    -- ignore tag-only headings
-    local is_tag = node:child_count() == 1 and node:child(0):type() == 'tag'
-    if not (is_code or is_table or is_tag) then
-      table.insert(headings, {
-        bufnr = bufnr,
-        lnum = row + 1,
-        text = (capture == 'h3' or capture == 'h4') and '  ' .. text or text,
-      })
-    end
-  end
-  vim.fn.setloclist(0, headings, ' ')
-  vim.fn.setloclist(0, {}, 'a', { title = 'Help TOC' })
-  vim.cmd.lopen()
-end
-
-return M