Improve documentation of 'expand-abbrev' and wrapper hooks

* lisp/simple.el (filter-buffer-substring-functions)
(buffer-substring--filter): Add a link to 'with-wrapper-hook' as
the place to look for documentation of wrapper hooks.
* lisp/minibuffer.el (completion-in-region-functions)
(completion--in-region): Add a link to 'with-wrapper-hook' as the
place to look for documentation of wrapper hooks.
* lisp/abbrev.el (expand-abbrev, abbrev--default-expand): Clarify
the doc strings.  (Bug#24540)

* doc/lispref/text.texi (Buffer Contents): Mention
'with-wrapper-hook's doc string as the place to learn about that
obsolete facility.

1 files changed, 5 insertions, 4 deletions

diff --git a/lisp/abbrev.el b/lisp/abbrev.el
index d181d97703e..8c4f6eb01b2 100644
--- a/lisp/abbrev.el
+++ b/lisp/abbrev.el
@@ -837,16 +837,17 @@ Takes no argument and should return the abbrev symbol if expansion took place.")
   "Expand the abbrev before point, if there is an abbrev there.
 Effective when explicitly called even when `abbrev-mode' is nil.
 Before doing anything else, runs `pre-abbrev-expand-hook'.
-Calls `abbrev-expand-function' with no argument to do the work,
-and returns whatever it does.  (This should be the abbrev symbol
-if expansion occurred, else nil.)"
+Calls the value of `abbrev-expand-function' with no argument to do
+the work, and returns whatever it does.  (That return value should
+be the abbrev symbol if expansion occurred, else nil.)"
   (interactive)
   (run-hooks 'pre-abbrev-expand-hook)
   (funcall abbrev-expand-function))
 
 (defun abbrev--default-expand ()
   "Default function to use for `abbrev-expand-function'.
-This respects the wrapper hook `abbrev-expand-functions'.
+This also respects the obsolete wrapper hook `abbrev-expand-functions'.
+\(See `with-wrapper-hook' for details about wrapper hooks.)
 Calls `abbrev-insert' to insert any expansion, and returns what it does."
   (with-wrapper-hook abbrev-expand-functions ()
     (pcase-let ((`(,sym ,name ,wordstart ,wordend) (abbrev--before-point)))