bug#40992: 27.0.90; Evaluating a function while using edebug breaks

[Noam Postavsky <npostavs@gmail.com>]

Lars Ingebrigtsen <larsi@gnus.org> writes:

> Alan Mackenzie <acm@muc.de> writes:
>
>> There doesn't appear to be a good way of solving this bug.  A workable
>> workaround would be to check that the 'edebug property value is a list
>> in edebug--overlay-breakpoints, and just to remove the breakpoint
>> highlights when it's not a list.  When it's not a list, it's a marker
>> pointing to the start of the function, from which the end of the
>> function can be found, to serve as the END argument to
>> edebug--overlay-breakpoints-remove.
>>
>> Or something like that.  :-(
>
> I think that sounds like a good solution on master, but the patch that
> introduced this should probably be reverted on emacs-27 -- it wasn't a
> bug fix, but a new feature, so reverting it should be safe, I think.

I don't understand; the fix looks trivial to me (leaving out
indentation), and only touches a new function.  Surely this is okay for
emacs-27?

--- i/lisp/emacs-lisp/edebug.el
+++ w/lisp/emacs-lisp/edebug.el
@@ -3236,8 +3236,9 @@ 'edebug-breakpoint
   "\x3c\x7e\xff\xff\xff\xff\x7e\x3c")
 
 (defun edebug--overlay-breakpoints (function)
-  (let* ((data (get function 'edebug))
-         (start (nth 0 data))
+  (let ((data (get function 'edebug)))
+    (when (listp data)
+      (let* ((start (nth 0 data))
          (breakpoints (nth 1 data))
          (offsets (nth 2 data)))
     ;; First remove all old breakpoint overlays.
@@ -3264,6 +3265,7 @@ edebug--overlay-breakpoints
                          (propertize
                           "x" 'display
                           `(left-fringe edebug-breakpoint ,face)))))))))
+    ))
 
 (defun edebug--overlay-breakpoints-remove (start end)
   (dolist (overlay (overlays-in start end))