From 0ee966dcb0d40ee347c1a8ea1a50609aa3aa1e28 Mon Sep 17 00:00:00 2001
From: Pierre Neidhardt <mail@ambrevar.xyz>
Date: Fri, 22 Jan 2021 21:16:03 +0100
Subject: [PATCH] SLY: Fix prompt navigation.

---
 .emacs.d/lisp/init-sly.el | 39 ++++++++++++++++++++++++++-------------
 1 file changed, 26 insertions(+), 13 deletions(-)

diff --git a/.emacs.d/lisp/init-sly.el b/.emacs.d/lisp/init-sly.el
index 5600b4f1..36d5b9b1 100644
--- a/.emacs.d/lisp/init-sly.el
+++ b/.emacs.d/lisp/init-sly.el
@@ -272,22 +272,35 @@ returns a string."
             #'ambrevar/sly-new-prompt)
     (advice-add 'sly-mrepl--insert-prompt :around #'ambrevar/sly-prepare-prompt)))
 
+(defun ambrevar/sly-end-of-prompt-p ()
+  (and (not (= (point) (point-min)))
+       (not (get-text-property (point) 'sly-mrepl--prompt))
+       (get-text-property (1- (point)) 'sly-mrepl--prompt)))
+
+(defun ambrevar/sly-prompt-line-p ()
+  (or (ambrevar/sly-end-of-prompt-p)
+      (save-excursion
+        (goto-char (line-beginning-position))
+        (ambrevar/sly-end-of-prompt-p))))
+
 (defun ambrevar/sly-mrepl-previous-prompt ()
   "Go to the beginning of the previous REPL prompt."
   (interactive)
-  ;; This has two wrinkles around the first prompt: (1) when going to
-  ;; the first prompt it leaves point at column 0 (1) when called from
-  ;; frist prompt goes to beginning of buffer.  The correct fix is to
-  ;; patch comint.el's comint-next-prompt and comint-previous-prompt
-  ;; anyway...
-  (let* ((inhibit-field-text-motion t)
-         (pos (previous-single-char-property-change
-               (previous-single-char-property-change (point)
-                'sly-mrepl--prompt)
-               'sly-mrepl--prompt)))
-    (goto-char pos)
-    (goto-char (line-beginning-position)))
-  (end-of-line))
+  (cl-flet ((go-back ()
+                     (goto-char
+                      (previous-single-char-property-change
+                       (point) 'sly-mrepl--prompt))))
+    (if (ambrevar/sly-prompt-line-p)
+        (progn
+          (unless (ambrevar/sly-end-of-prompt-p)
+            (goto-char (line-beginning-position)))
+          (go-back)
+          (go-back))
+      (go-back))
+    (unless (ambrevar/sly-prompt-line-p)
+      ;; We did not end up on a prompt, means we are above the first prompt.
+      ;; Return back.
+      (ambrevar/sly-mrepl-next-prompt))))
 
 (defun ambrevar/sly-mrepl-next-prompt ()
   "Go to the beginning of the next REPL prompt."