From fdfb18c16d1d38a197bc1143d2704aefa7fe9daf 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     | 11 +++++++++++
 lisp/ielm.el | 15 +++++++++++++++
 2 files changed, 26 insertions(+)

diff --git a/etc/NEWS b/etc/NEWS
index bce33f96aee..c20d34b39ad 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -1243,6 +1243,17 @@ 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 variable 'ielm-history-file-name'.
+If non-nil, name of the file to read/write IELM input history.  Set to
+nil to revert IELM to the old behavior of not remembering input
+history between sessions.
+
 
 * New Modes and Packages in Emacs 30.1
 
diff --git a/lisp/ielm.el b/lisp/ielm.el
index 777aebb70cf..cfb51b7a94e 100644
--- a/lisp/ielm.el
+++ b/lisp/ielm.el
@@ -110,6 +110,13 @@ ielm-dynamic-multiline-inputs
 such as `edebug-defun' to work with such inputs."
   :type 'boolean)
 
+(defcustom ielm-history-file-name
+  (locate-user-emacs-file "ielm-history.eld")
+  "If non-nil, name of the file to read/write IELM input history."
+  :type '(choice (const :tag "nil" nil)
+		 file)
+  :version "30.1")
+
 (defvaralias 'inferior-emacs-lisp-mode-hook 'ielm-mode-hook)
 (defcustom ielm-mode-hook nil
   "Hooks to be run when IELM (`inferior-emacs-lisp-mode') is started."
@@ -605,6 +612,11 @@ 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 +643,9 @@ 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
-- 
2.42.0