bug#34506: 27.0.50: push-button bug with basic text-property button

[Basil L. Contovounesios]

Robert Weiner <rswgnu@gmail.com> writes:

>> On Feb 19, 2019, at 10:26 AM, Basil L. Contovounesios <contovob@tcd.ie> 
>> wrote:
>> 
>> I don't see why anyone
>>   would mix widgets and buttons in the same buffer and run the risk of
>>   such gotchas.  I believe this contributed in part to Robert's
>>   confusion.
>
> If buttons and widgets are wholly incompatible and separate then button-at
> should return nil when on a widget even if both buttons and widgets use the 
> same
> underlying mechanism.

How's the following?

diff --git a/lisp/button.el b/lisp/button.el
index c46f3d9a52..921e84dfa6 100644
--- a/lisp/button.el
+++ b/lisp/button.el
@@ -382,10 +382,12 @@ button-at
 If the button at POS is a text property button, the return value
 is a marker pointing to POS."
   (let ((button (get-char-property pos 'button)))
-    (if (or (overlayp button) (null button))
-       button
-      ;; Must be a text-property button; return a marker pointing to it.
-      (copy-marker pos t))))
+    (and button (get-char-property pos 'category)
+         (if (overlayp button)
+             button
+           ;; Must be a text-property button;
+           ;; return a marker pointing to it.
+           (copy-marker pos t)))))
 
 (defun next-button (pos &optional count-current)
   "Return the next button after position POS in the current buffer.
diff --git a/lisp/wid-edit.el b/lisp/wid-edit.el
index 52c0b5b74d..b9f98cdc4c 100644
--- a/lisp/wid-edit.el
+++ b/lisp/wid-edit.el
@@ -1163,8 +1163,9 @@ widget-field-list
 
 (defun widget-at (&optional pos)
   "The button or field at POS (default, point)."
-  (or (get-char-property (or pos (point)) 'button)
-      (widget-field-at pos)))
+  (let ((widget (or (get-char-property (or pos (point)) 'button)
+                    (widget-field-at pos))))
+    (and (widgetp widget) widget)))
 
 ;;;###autoload
 (defun widget-setup ()

-- 
Basil