bug#36564: 27.0.50; Wrong number of errors in compilation mode-line

[Juri Linkov]

>> --- a/lisp/progmodes/compile.el
>> +++ b/lisp/progmodes/compile.el
>> @@ -2245,6 +2250,8 @@ compilation-filter
>>                (unless comint-inhibit-carriage-motion
>>                  (comint-carriage-motion (process-mark proc) (point)))
>>                (set-marker (process-mark proc) (point))
>> +              ;; Update the number of errors in compilation-mode-line-errors
>> +              (font-lock-ensure compilation-filter-start (point))
>
> I worry that doing it there will slow down processing too much.
> But even if we want to do it there, I think font-lock-ensure is wrong
> because we shouldn't *highlight* (e.g. the user may prefer font-lock to
> be disabled).
>
> Does compilation--ensure-parse do what you want?

I tried compilation--ensure-parse, and it updates the number of errors,
so I replaced font-lock-ensure with compilation--ensure-parse.