bug#27281: Fix nlinum missing line numbers.

[npostavs]

Alex <agrambot@gmail.com> writes:
>>
>> This sounds like a workaround, possibly to a bug in jit-lock.  Or
>> perhaps we need to return a list of the form (jit-lock-bounds BEG END)
>> from nlinum--region?
>
> FWIW I've encountered this issue before and this diff does not solve the
> problem for me. I mostly see it when using the 3rd-party package
> macroexpand with nlinum. Expanding and closing a macro will leave
> several lines with no line number (from the 2nd line of the macro until
> the last line of the macro).
>
> I've tried to use edebug on nlinum--region to figure out what's going
> on, but it doesn't seem to be triggering for some reason.

I suspect the debugger is suppressed while jit-lock occurs.  You would
need to log things silently and print it later.  I think
'jit-lock--run-functions' and 'jit-lock-fontify-now' would be
interesting targets.  Something easy to check would be if there are
certain values of 'jit-lock-functions' needed to trigger this (apart
from nlinum--region of course).  Here's my guess as to a fix (untested):

--- i/packages/nlinum/nlinum.el
+++ w/packages/nlinum/nlinum.el
@@ -296,7 +296,8 @@ (defun nlinum--region (start limit)
   (save-excursion
     ;; Text may contain those nasty intangible properties, but
     ;; that shouldn't prevent us from counting those lines.
-    (let ((inhibit-point-motion-hooks t))
+    (let ((inhibit-point-motion-hooks t)
+          (end start))
       (goto-char start)
       (unless (bolp) (forward-line 1))
       (remove-overlays (point) limit 'nlinum t)
@@ -320,9 +321,10 @@ (defun nlinum--region (start limit)
                    ;;   (run-with-idle-timer 0.5 nil #'nlinum--flush-overlays
                    ;;                        (current-buffer)))
                    (setq line (1+ line))
-                   (zerop (forward-line 1))))))))
-  ;; (setq nlinum--desc (format "-%d" (nlinum--ol-count)))
-  nil)
+                   (setq end (line-end-position))
+                   (zerop (forward-line 1)))))))
+    ;; (setq nlinum--desc (format "-%d" (nlinum--ol-count)))
+    `(jit-lock-bounds ,start . ,end)))
 
 ;;;###autoload
 (define-globalized-minor-mode global-nlinum-mode nlinum-mode