On Sun, 31 Jan 2021 20:08:18 +0100 Stephen Berman <stephen.berman@gmx.net> wrote:

> 0. emacs -Q
> 1. In the following find-dired invocation adjust `<emacs/lisp>' to the
> emacs lisp source directory and then evaluate the sexp:
> (find-dired "<emacs/lisp>" "-name \"*.el\" -exec grep 'const' {} \";\"")
> => error in process filter: Invalid use of ‘\’ in replacement text
>
> This also happens with Emacs 27 but not with Emacs 26.
[...]

It occurred to me that invoking `(dired--align-all-files)' in
find-dired-sentinel might render the realigning code in
find-dired-filter superfluous.  But it turns out -- if I didn't make a
mistake or overlook something in testing -- that simply removing the
realigning code in find-dired-filter, without adding
`(dired--align-all-files)' to find-dired-sentinel, fixes all the
problems reported in this bug as well as in Bug#29803.  That is, I am
now proposing the following patch instead of the one in my previous
post: