I am getting the character under the cursor in vimscript the following way:
getline(\'.\')[col(\'.\')-1]
It works exactly like it should,
nr2char(strgetchar(getline('.')[col('.') - 1:], 0))
or
strcharpart(getline('.')[col('.') - 1:], 0, 1)
Though I cannot reproduce the problem you're describing, there's another problem with your code: Because of the string indexing (and this is one of the uglier sides of Vimscript), it only works with single-byte characters, but will fail to capture chars like Ä
or
Another way to get the character index under cursor that deal with both ASCII and non-ASCII characters is the like the following:
function! CharAtIdx(str, idx) abort
" Get char at idx from str. Note that this is based on character index
" instead of the byte index.
return strcharpart(a:str, a:idx, 1)
endfunction
function! CursorCharIdx() abort
" A more concise way to get character index under cursor.
let cursor_byte_idx = col('.')
if cursor_byte_idx == 1
return 0
endif
let pre_cursor_text = getline('.')[:col('.')-2]
return strchars(pre_cursor_text)
endfunction
Then if you want to get char under cursor, use the following command:
let cur_char_idx = CursorCharIdx()
let cur_char = CharAtIdx(getline('.'), cur_char_idx)
See also this post on how to get pre-cursor char.