Fix cursor position following multibyte characters

CHANGELOG.md

@@ -10,6 +10,9 @@
 - Avoid creating public functions for callbacks which should be temporary.
 - Fix file edits in buffers that aren't current when the current buffer is
   shorter than the buffer being edited.
+- Fix character positions when the cursor is on a line following multibyte
+  characters for recent versions of vim. Older versions and neovim continue to
+  have incorrect positions.
 
 **Minor breaking changes**
 - Remove `noselect` from the default `completeopts` used during autocompletion.

autoload/lsc/complete.vim

@@ -63,7 +63,7 @@ function! s:isCompletable() abort
     return v:false
   endif
   if s:next_char !~# '\w' | return v:false | endif
-  let l:cur_col = col('.')
+  let l:cur_col = lsc#util#currentChar()
   let l:min_length = exists('g:lsc_autocomplete_length') ?
       \ g:lsc_autocomplete_length : 3
   if l:min_length == v:false | return v:false | endif
@@ -108,8 +108,8 @@ function! s:SuggestCompletions(items) abort
     return
   endif
   let l:start = s:FindStart(a:items)
-  let l:base = l:start != col('.')
-      \ ? getline('.')[l:start - 1:col('.') - 2]
+  let l:base = l:start != lsc#util#currentChar()
+      \ ? getline('.')[l:start - 1:lsc#util#currentChar() - 2]
       \ : ''
   let l:completion_items = s:CompletionItems(l:base, a:items)
   call s:SetCompleteOpt()
@@ -169,7 +169,7 @@ endfunction
 " Finds the 1-based index of the character after the last non word character
 " behind the cursor.
 function! s:GuessCompletionStart() abort
-  let l:search = col('.') - 2
+  let l:search = lsc#util#currentChar() - 2
   let l:line = getline('.')
   while l:search > 0
     let l:char = l:line[l:search]

autoload/lsc/cursor.vim

@@ -120,7 +120,7 @@ endfunction
 " not in any reference.
 function! lsc#cursor#isInReference(references) abort
   let l:line = line('.')
-  let l:col = col('.')
+  let l:col = lsc#util#currentChar()
   let l:idx = 0
   for l:reference in a:references
     for l:range in l:reference.ranges

autoload/lsc/diagnostics.vim

@@ -346,7 +346,7 @@ function! lsc#diagnostics#underCursor() abort
     return {}
   endif
   let l:diagnostics = l:file_diagnostics[l:line]
-  let l:col = col('.')
+  let l:col = lsc#util#currentChar()
   let l:closest_diagnostic = {}
   let l:closest_distance = -1
   let l:closest_is_within = v:false

autoload/lsc/params.vim

@@ -4,14 +4,19 @@ endfunction
 
 function! lsc#params#documentPosition() abort
   return { 'textDocument': {'uri': lsc#uri#documentUri()},
-      \ 'position': {'line': line('.') - 1, 'character': col('.') - 1}
+      \ 'position': {
+      \   'line': line('.') - 1,
+      \   'character': lsc#util#currentChar() - 1
       \ }
+      \}
 endfunction
-
 function! lsc#params#documentRange() abort
   return { 'textDocument': {'uri': lsc#uri#documentUri()},
       \ 'range': {
-      \   'start': {'line': line('.') - 1, 'character': col('.') - 1},
-      \   'end': {'line': line('.') - 1, 'character': col('.')}},
-      \ }
+      \   'start': {
+      \     'line': line('.') - 1,
+      \     'character': lsc#util#currentChar() - 1,
+      \    },
+      \  'end': {'line': line('.') - 1, 'character': lsc#util#currentChar()}},
+      \}
 endfunction

autoload/lsc/util.vim

@@ -170,3 +170,15 @@ function! s:IgnoreArgs(name, Callback, args, ...) abort
     let g:lsc_last_error_callback = [a:Callback, a:args]
   endtry
 endfunction
+
+if exists('*charcol')
+  function! lsc#util#currentChar()
+    return charcol('.')
+  endfunction
+else
+  function! lsc#util#currentChar()
+    " TODO - Can charcol be implemented manually?
+    " For now, vim without charcol does not handle multibyte characters
+    return col('.')
+  endfunction
+endif