Resolve syntax highlighting group in neovim/treesitter (#160)

Co-authored-by: Junegunn Choi <junegunn.c@gmail.com>

README.md

@@ -406,7 +406,7 @@ highlighted as code comments or strings are ignored.
 ```vim
 " Default:
 "   If a delimiter is in a highlight group whose name matches
-"   any of the followings, it will be ignored.
+"   any of the following regular expressions, it will be ignored.
 let g:easy_align_ignore_groups = ['Comment', 'String']
 ```
 
@@ -463,6 +463,19 @@ If a pattern in `ignore_groups` is prepended by a `!`, it will have the opposite
 meaning. For instance, if `ignore_groups` is given as `['!Comment']`, delimiters
 that are *not* highlighted as Comment will be ignored during the alignment.
 
+To make `ignore_groups` work, and to debug the related issues, it is useful to
+know which highlight group a certain location in a file belongs to. A special
+function exists for this purpose, returning exactly the name of the highlight
+group that is used by the easy align plugin.
+
+```vim
+" Highlight group name of the cursor position
+echo easy_align#get_highlight_group_name()
+
+" Highlight group name of the line 10, column 20
+echo easy_align#get_highlight_group_name(10, 20)
+```
+
 ### Ignoring unmatched lines
 
 `ignore_unmatched` option determines how EasyAlign command processes lines that

autoload/easy_align.vim

@@ -89,9 +89,30 @@ function! s:floor2(v)
   return a:v % 2 == 0 ? a:v : a:v - 1
 endfunction
 
+function! s:get_highlight_group_name(line, col)
+  let hl = synIDattr(synID(a:line, a:col, 0), 'name')
+
+  if hl == '' && has('nvim-0.9.0')
+    let insp = luaeval('vim.inspect_pos and vim.inspect_pos( nil, ' .. (a:line-1) .. ', ' .. (a:col-1) .. ' ) or { treesitter = {} }')
+    if !empty(insp.treesitter)
+      let hl = insp.treesitter[0].hl_group_link
+    endif
+  endif
+
+  " and, finally
+  return hl
+endfunction
+
+function! easy_align#get_highlight_group_name(...)
+  let l  = get(a:, 1, line('.'))
+  let c  = get(a:, 2, col('.'))
+  let hl = s:get_highlight_group_name(l, c)
+  return { 'line': l, 'column': c, 'group': hl }
+endfunction
+
 function! s:highlighted_as(line, col, groups)
   if empty(a:groups) | return 0 | endif
-  let hl = synIDattr(synID(a:line, a:col, 0), 'name')
+  let hl = s:get_highlight_group_name(a:line, a:col)
   for grp in a:groups
     if grp[0] == '!'
       if hl !~# grp[1:-1]
@@ -1146,3 +1167,4 @@ endfunction
 let &cpo = s:cpo_save
 unlet s:cpo_save
 
+" vim: set et sw=2 :

doc/easy_align.txt

@@ -517,7 +517,7 @@ highlighted as code comments or strings are ignored.
 >
     " Default:
     "   If a delimiter is in a highlight group whose name matches
-    "   any of the followings, it will be ignored.
+    "   any of the following regular expressions, it will be ignored.
     let g:easy_align_ignore_groups = ['Comment', 'String']
 <
 For example, the following paragraph
@@ -567,6 +567,17 @@ opposite meaning. For instance, if `ignore_groups` is given as `['!Comment']`,
 delimiters that are not highlighted as Comment will be ignored during the
 alignment.
 
+To make `ignore_groups` work, and to debug the related issues, it is useful to
+know which highlight group a certain location in a file belongs to. A special
+function exists for this purpose, returning exactly the name of the highlight
+group that is used by the easy align plugin.
+>
+    " Highlight group name of the cursor position
+    echo easy_align#get_highlight_group_name()
+
+    " Highlight group name of the line 10, column 20
+    echo easy_align#get_highlight_group_name(10, 20)
+<
 
 < Ignoring unmatched lines >__________________________________________________~
                                            *easy-align-ignoring-unmatched-lines*

plugin/easy_align.vim

@@ -140,3 +140,4 @@ vnoremap <silent> <Plug>(EasyAlignRepeat) :<C-U>call <SID>repeat_in_visual()<Ent
 " Backward-compatibility (deprecated)
 nnoremap <silent> <Plug>(EasyAlignOperator) :set opfunc=<SID>easy_align_op<Enter>g@
 
+" vim: set et sw=2 :