From da08aa2d7d9ca9197896e7988dc8785006796336 Mon Sep 17 00:00:00 2001
From: Henrik Lissner <git@henrik.io>
Date: Thu, 28 Nov 2024 16:09:44 -0500
Subject: [PATCH] feat(lib): backport major-mode-remap{,-alist}

Will be necessary for treesit.el support coming to the :tools
tree-sitter module later.
---
 lisp/doom-compat.el | 28 ++++++++++++++++++++++++++++
 1 file changed, 28 insertions(+)

diff --git a/lisp/doom-compat.el b/lisp/doom-compat.el
index fe9e5edb7..726332622 100644
--- a/lisp/doom-compat.el
+++ b/lisp/doom-compat.el
@@ -109,5 +109,33 @@ and return the value found in PLACE instead."
 (unless (fboundp 'bol) (defalias 'bol #'line-beginning-position))
 (unless (fboundp 'eol) (defalias 'eol #'line-end-position))
 
+;; Introduced in Emacs 29+
+(unless (boundp 'major-mode-remap-alist)
+  (defvar major-mode-remap-alist nil)
+  (defvar-local set-auto-mode--last nil)
+  (define-advice set-auto-mode-0 (:override (mode &optional keep-mode-if-same) backport-major-mode-remap)
+    (unless (and keep-mode-if-same
+                 (or (eq (indirect-function mode)
+                         (indirect-function major-mode))
+                     (and set-auto-mode--last
+                          (eq mode (car set-auto-mode--last))
+                          (eq major-mode (cdr set-auto-mode--last)))))
+      (when mode
+        (funcall (major-mode-remap mode))
+        (unless (eq mode major-mode)
+          (setq set-auto-mode--last (cons mode major-mode)))
+        mode))))
+
+
+;;; From Emacs 30+
+;; Introduced in Emacs 30+
+(unless (fboundp 'major-mode-remap)
+  (defvar major-mode-remap-defaults nil)
+  (defun major-mode-remap (mode)
+    "Return the function to use to enable MODE."
+    (or (cdr (or (assq mode major-mode-remap-alist)
+                 (assq mode major-mode-remap-defaults)))
+        mode)))
+
 (provide 'doom-compat)
 ;;; doom-compat.el ends here