From 3ac85190a90fd85bb7a960cd4895c3bd4e41b085 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Simen=20Heggest=C3=B8yl?= <simenheg@runbox.com>
Date: Wed, 8 Nov 2023 16:08:08 +0100
Subject: [PATCH] Add support for reading/writing IELM input history

* lisp/ielm.el (inferior-emacs-lisp-mode): Add support for
reading/writing input history.
(ielm--history-file-name): Name of the file to read/write IELM input
history.
---
 etc/NEWS     |  5 +++++
 lisp/ielm.el | 12 ++++++++++++
 2 files changed, 17 insertions(+)

diff --git a/etc/NEWS b/etc/NEWS
index 1cdb12c3958..f65d53e4827 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -1216,6 +1216,11 @@ chat buffers use by default.
 *** New command 'customize-dirlocals'.
 This command pops up a buffer to edit the settings in ".dir-locals.el".
 
+** IELM
+
+---
+*** IELM now remembers input history between sessions.
+
 
 * New Modes and Packages in Emacs 30.1
 
diff --git a/lisp/ielm.el b/lisp/ielm.el
index 777aebb70cf..46a2a1799da 100644
--- a/lisp/ielm.el
+++ b/lisp/ielm.el
@@ -152,6 +152,10 @@ ielm-header
 \\[describe-mode] for help.\n"
   "Message to display when IELM is started.")
 
+(defvar ielm--history-file-name
+  (locate-user-emacs-file "ielm-history.el")
+  "Name of the file to read/write IELM input history.")
+
 (defvaralias 'inferior-emacs-lisp-mode-map 'ielm-map)
 (defvar-keymap ielm-map
   :doc "Keymap for IELM mode."
@@ -605,6 +609,11 @@ inferior-emacs-lisp-mode
             #'ielm-indirect-setup-hook 'append t)
   (setq comint-indirect-setup-function #'emacs-lisp-mode)
 
+  ;; Input history
+  (setq-local comint-input-ring-file-name ielm--history-file-name)
+  (setq-local kill-buffer-hook #'comint-write-input-ring)
+  (comint-read-input-ring t)
+
   ;; A dummy process to keep comint happy. It will never get any input
   (unless (comint-check-proc (current-buffer))
     ;; Was cat, but on non-Unix platforms that might not exist, so
@@ -631,6 +640,9 @@ inferior-emacs-lisp-mode
     (set-marker comint-last-input-start (ielm-pm))
     (set-process-filter (get-buffer-process (current-buffer)) 'comint-output-filter)))
 
+(unless noninteractive
+  (add-hook 'kill-emacs-hook #'comint-write-input-ring))
+
 (defun ielm-get-old-input nil
   ;; Return the previous input surrounding point
   (save-excursion
-- 
2.39.2