Subject: 27.0.91; [PATCH] Eldoc describes the wrong function when reading an expression from the minibuffer

From: Daniel Koning <[email-masked]>
Date: Tue, 09 Jun 2020 21:56:14 -0500

Severity: minor
Tags: patch

The Eldoc message shows the documentation for the wrong function (or no
documentation at all) in this specific situation:

(a) You're typing an elisp expression into `read-from-minibuffer', and
(b) the function name contains punctuation, such as ! or ?, whose
character class is "punctuation" and not "symbol" in the standard syntax
table.

Function names as described in (b) are not only legal but quite common
in third-party code. There aren't many in the standard distribution, but
you'll notice a few here and there. Try this:

(require 'pcvs)
(call-interactively #'eval-expression)
-----
Eval: (cvs-mode!
-----

The mode line shows the documentation for `cvs-mode' (without the !),
which is a different function and has a different lambda list.

This is happening because the syntax table in the minibuffer never gets
changed to the elisp table, which acknowledges all the valid symbol
characters as part of the "symbol" class.

There are a couple different spots in the code to which you could
attribute this lapse. For one, the elisp-mode.el function
`elisp--current-symbol' isn't wrapped in a `with-syntax-table', unlike
other similar definitions in the same file. I think anyone invoking this
function could reasonably expect it to observe elisp syntax, so that's
what my tiny patch addresses. This fixes the Eldoc problem.

But here's another weird thing further down the call stack.
`read--expression' has a FIXME comment saying to turn on
`emacs-lisp-mode' in the minibuffer -- which would also set the
appropriate syntax table -- but it doesn't actually do it. I guess that
must not work for whatever reason (since it has to have taken longer to
write the comment than it would have taken to add the code). Should it
be changed now so that it does set the major mode? Is there a problem
with specialized major modes in the minibuffer? I hereby kick the can
over to whoever knows more.

Daniel

>From 1d4ed0e89b4ebc040609b7476128062685843c7f Mon Sep 17 00:00:00 2001
From: Daniel Koning <[email-masked]>
Date: Tue, 9 Jun 2020 19:24:11 -0500
Subject: [PATCH] lisp/progmodes/elisp-mode.el (elisp--current-symbol): Set
 syntax table.

Even if `elisp-current-symbol' is called from a buffer with a different
active syntax table (such as the minibuffer in `read-from-minibuffer'),
use `emacs-lisp-mode-syntax-table' to determine the symbol boundaries.

Copyright-paperwork-exempt: yes
---
 lisp/progmodes/elisp-mode.el | 9 +++++----
 1 file changed, 5 insertions(+), 4 deletions(-)

diff --git a/lisp/progmodes/elisp-mode.el b/lisp/progmodes/elisp-mode.el
index f39ecf9b7b..65c01b2ce1 100644
--- a/lisp/progmodes/elisp-mode.el
+++ b/lisp/progmodes/elisp-mode.el
@@ -1615,10 +1615,11 @@ elisp--beginning-of-sexp
 
 ;; returns nil unless current word is an interned symbol.
 (defun elisp--current-symbol ()
-  (let ((c (char-after (point))))
-    (and c
-         (memq (char-syntax c) '(?w ?_))
-         (intern-soft (current-word)))))
+  (with-syntax-table emacs-lisp-mode-syntax-table
+    (let ((c (char-after (point))))
+      (and c
+           (memq (char-syntax c) '(?w ?_))
+           (intern-soft (current-word))))))
 
 (defun elisp-function-argstring (arglist)
   "Return ARGLIST as a string enclosed by ().
-- 
2.20.1