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'vtable-update-object' can now be called with one argument

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It's often necessary to update the representation of a single
object in a table (e.g a struct, whose identity does not change
when its slots'
values are changed).  To do so, now the function may be called
like this:

  (vtable-update-object table object)

Instead of like this:

  (vtable-update-object table object object)

This also documents the behavior of the just-discovered limitation filed
as bug#69837.
* lisp/emacs-lisp/vtable.el (vtable-update-object): Make 'old-object'
argument optional.  (Bug#69666)

* doc/misc/vtable.texi (Interface Functions): Update documentation.

* etc/NEWS: Add news entry.
This commit is contained in:
Adam Porter 2024-03-08 23:43:14 -06:00 • committed by Eli Zaretskii
parent fe24a8c3c0
commit 393f58c85a
3 changed files with 32 additions and 5 deletions
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15
lisp/emacs-lisp/vtable.el
View file

@ -283,8 +283,16 @@ If it can't be found, return nil and don't move point."
(goto-char (prop-match-beginning match))
(end-of-line)))
(defun vtable-update-object (table object old-object)
"Replace OLD-OBJECT in TABLE with OBJECT."
(defun vtable-update-object (table object &optional old-object)
"Update OBJECT's representation in TABLE.
If OLD-OBJECT is non-nil, replace OLD-OBJECT with OBJECT and display it.
In either case, if the existing object is not found in the table (being
compared with `equal'), signal an error. Note a limitation: if TABLE's
buffer is not in a visible window, or if its window has changed width
since it was updated, updating the TABLE is not possible, and an error
is signaled."
(unless old-object
(setq old-object object))
(let* ((objects (vtable-objects table))
(inhibit-read-only t))
;; First replace the object in the object storage.
@ -300,6 +308,9 @@ If it can't be found, return nil and don't move point."
(error "Can't find the old object"))
(setcar (cdr objects) object))
;; Then update the cache...
;; FIXME: If the table's buffer has no visible window, or if its
;; width has changed since the table was updated, the cache key will
;; not match and the object can't be updated. (Bug #69837).
(if-let ((line-number (seq-position (car (vtable--cache table)) old-object
(lambda (a b)
(equal (car a) b))))