From 043cb51802b096a56133667fc63e89d3861591a7 Mon Sep 17 00:00:00 2001
From: Yuan Fu <casouri@gmail.com>
Date: Sun, 21 Apr 2024 21:25:19 -0700
Subject: [PATCH] Add tree-sitter comment-indent-new-line (bug#70074)

* lisp/progmodes/c-ts-common.el:
(c-ts-common-comment-indent-new-line): New function.
(c-ts-common-comment-setup): Setup comment-line-break-function and
comment-multi-line.

(cherry picked from commit 81391ae3f52a41f30137642976ae06dd49572bfe)
---
 lisp/progmodes/c-ts-common.el | 50 +++++++++++++++++++++++++++++++++--
 1 file changed, 48 insertions(+), 2 deletions(-)

diff --git a/lisp/progmodes/c-ts-common.el b/lisp/progmodes/c-ts-common.el
index e48bcc64f14..298fb3cd074 100644
--- a/lisp/progmodes/c-ts-common.el
+++ b/lisp/progmodes/c-ts-common.el
@@ -221,7 +221,9 @@ Set up:
  - `adaptive-fill-first-line-regexp'
  - `paragraph-start'
  - `paragraph-separate'
- - `fill-paragraph-function'"
+ - `fill-paragraph-function'
+ - `comment-line-break-function'
+ - `comment-multi-line'"
   (setq-local comment-start "// ")
   (setq-local comment-end "")
   (setq-local comment-start-skip (rx (or (seq "/" (+ "/"))
@@ -267,7 +269,51 @@ Set up:
                            eol)
                       "\f")))
   (setq-local paragraph-separate paragraph-start)
-  (setq-local fill-paragraph-function #'c-ts-common--fill-paragraph))
+  (setq-local fill-paragraph-function #'c-ts-common--fill-paragraph)
+
+  (setq-local comment-line-break-function
+              #'c-ts-common-comment-indent-new-line)
+  (setq-local comment-multi-line t))
+
+(defun c-ts-common-comment-indent-new-line (&optional soft)
+  "Break line at point and indent, continuing comment if within one.
+
+This is like `comment-indent-new-line', but specialized for C-style //
+and /* */ comments.  SOFT works the same as in
+`comment-indent-new-line'."
+  ;; I want to experiment with explicitly listing out all each cases and
+  ;; handle them separately, as opposed to fiddling with `comment-start'
+  ;; and friends.  This will have more duplicate code and will be less
+  ;; generic, but in the same time might save us from writting cryptic
+  ;; code to handle all sorts of edge cases.
+  ;;
+  ;; For this command, let's try to make it basic: if the current line
+  ;; is a // comment, insert a newline and a // prefix; if the current
+  ;; line is in a /* comment, insert a newline and a * prefix.  No
+  ;; auto-fill or other smart features.
+  (cond
+   ((save-excursion
+      (beginning-of-line)
+      (looking-at (rx "//" (group (* " ")))))
+    (let ((whitespaces (match-string 1)))
+      (if soft (insert-and-inherit ?\n) (newline 1))
+      (delete-region (point) (line-end-position))
+      (insert "//" whitespaces)))
+
+   ((save-excursion
+      (beginning-of-line)
+      (looking-at (rx "/*")))
+    (if soft (insert-and-inherit ?\n) (newline 1))
+    (delete-region (point) (line-end-position))
+    (insert " *"))
+
+   ((save-excursion
+      (beginning-of-line)
+      (looking-at (rx (group (* " ") (or "*" "|") (* " ")))))
+    (let ((prefix (match-string 1)))
+      (if soft (insert-and-inherit ?\n) (newline 1))
+      (delete-region (point) (line-end-position))
+      (insert prefix)))))
 
 ;;; Statement indent
 
-- 
2.39.5