bug#69003: 29.2; IELM: Improve ielm-dynamic-return when electric-pair-mode is enabled

[Sean Devlin]

Hi folks,

This is a feature request.

IELM has an existing customization ielm-dynamic-return with DWIM
behavior when typing RET. If there is a complete sexp at the prompt, it
is evaluated; otherwise, it inserts a newline and indents.

This is a great feature, but it doesn't work as well if you have
electric-pair-mode (or similar) enabled. Since the closing parenthesis
is inserted automatically, you almost always have a complete sexp at the
prompt.

Here's a recipe to reproduce a frustrating interaction:

1. Emacs -Q
2. M-x electric-pair-mode
3. M-x ielm
4. Type the text: "(defun my-function ()"
5. Due to electric-pair-mode, this is what the prompt now looks like
(with the "|" character representing the point):

IELM> (defun my-function ()|)

6. Type RET
7. IELM evaluates the input

What I really wanted was to continue editing the function, but since
electric-pair-mode and ielm-dynamic-return are both enabled, IELM
evaluated the function prematurely.

It would be great to extend ielm-dynamic-return to improve handling of
this case. In my own configuration, I have RET bound to a function that
also checks whether point is at the end of the line:

(defun my-ielm-return ()
  (interactive)
  (if (eolp)
      (ielm-return)
    (newline-and-indent)))

Maybe ielm-dynamic-return could accept some third option that implements
similar logic.

Thanks!

In GNU Emacs 29.2 (build 1, aarch64-apple-darwin21.6.0, NS
appkit-2113.60 Version 12.6.6 (Build 21G646)) of 2024-01-18 built on
armbob.lan
Windowing system distributor 'Apple'
System Description:  macOS 14

Configured using:
'configure --with-ns '--enable-locallisppath=/Library/Application
Support/Emacs/${version}/site-lisp:/Library/Application
Support/Emacs/site-lisp' --with-modules 'CFLAGS=-DFD_SETSIZE=10000
-DDARWIN_UNLIMITED_SELECT' --with-x-toolkit=no'

Configured features:
ACL GLIB GMP GNUTLS JPEG JSON LIBXML2 MODULES NOTIFY KQUEUE NS PDUMPER
PNG RSVG SQLITE3 THREADS TIFF TOOLKIT_SCROLL_BARS TREE_SITTER ZLIB

Important settings:
  value of $LANG: en_US.UTF-8
  locale-coding-system: utf-8-unix

Major mode: IELM

Minor modes in effect:
  electric-pair-mode: t
  comint-fontify-input-mode: t
  tooltip-mode: t
  global-eldoc-mode: t
  eldoc-mode: t
  show-paren-mode: t
  electric-indent-mode: t
  mouse-wheel-mode: t
  tool-bar-mode: t
  menu-bar-mode: t
  file-name-shadow-mode: t
  global-font-lock-mode: t
  font-lock-mode: t
  blink-cursor-mode: t
  line-number-mode: t
  indent-tabs-mode: t
  transient-mark-mode: t
  auto-composition-mode: t
  auto-encryption-mode: t
  auto-compression-mode: t

Load-path shadows:
None found.

Features:
(help-mode shadow sort mail-extr emacsbug message mailcap yank-media
puny dired dired-loaddefs rfc822 mml mml-sec password-cache epa derived
epg rfc6068 epg-config gnus-util text-property-search mm-decode
mm-bodies mm-encode mail-parse rfc2231 mailabbrev gmm-utils mailheader
sendmail rfc2047 rfc2045 ietf-drums mm-util mail-prsvr mail-utils
elec-pair time-date subr-x tabify cus-edit cus-start cus-load icons
wid-edit cl-print byte-opt gv bytecomp byte-compile ielm pp cl-loaddefs
cl-lib comint ansi-osc ansi-color ring rmc iso-transl tooltip cconv
eldoc paren electric uniquify ediff-hook vc-hooks lisp-float-type
elisp-mode mwheel term/ns-win ns-win ucs-normalize mule-util
term/common-win tool-bar dnd fontset image regexp-opt fringe
tabulated-list replace newcomment text-mode lisp-mode prog-mode register
page tab-bar menu-bar rfn-eshadow isearch easymenu timer select
scroll-bar mouse jit-lock font-lock syntax font-core term/tty-colors
frame minibuffer nadvice seq simple cl-generic indonesian philippine
cham georgian utf-8-lang misc-lang vietnamese tibetan thai tai-viet lao
korean japanese eucjp-ms cp51932 hebrew greek romanian slovak czech
european ethiopic indian cyrillic chinese composite emoji-zwj charscript
charprop case-table epa-hook jka-cmpr-hook help abbrev obarray oclosure
cl-preloaded button loaddefs theme-loaddefs faces cus-face macroexp
files window text-properties overlay sha1 md5 base64 format env
code-pages mule custom widget keymap hashtable-print-readable backquote
threads kqueue cocoa ns multi-tty make-network-process emacs)

Memory information:
((conses 16 74075 12853)
(symbols 48 7865 3)
(strings 32 21108 1243)
(string-bytes 1 631584)
(vectors 16 14461)
(vector-slots 8 201600 14743)
(floats 8 34 30)
(intervals 56 461 6)
(buffers 984 17))