fix(tree-sitter): backport treesit-{enabled-modes,major-mode-remap-alist}

And ignore `treesit-major-mode-remap-alist`, because they could
interfere with our UX improvements.

modules/tools/tree-sitter/autoload/compat-30.el

@@ -40,4 +40,32 @@ Tree-sitter grammar for `%s' is missing; install it?"
         ;; Check that the grammar was installed successfully
         (treesit-ready-p lang))))
 
+;;; Introduced in later commits of 31.X
+;;;###autoload
+(unless (boundp 'treesit-major-mode-remap-alist)
+  (defvar treesit-major-mode-remap-alist nil))
+
+;;;###autoload
+(defcustom treesit-enabled-modes nil
+  "Specify what treesit modes to enable by default.
+The value can be either a list of ts-modes to enable,
+or t to enable all ts-modes."
+  :type `(choice
+          (const :tag "Disable all automatic associations" nil)
+          (const :tag "Enable all available ts-modes" t)
+          (set :tag "List of enabled ts-modes"
+               ,@(when (treesit-available-p)
+                   (sort (mapcar (lambda (m) `(function-item ,m))
+                                 (seq-uniq (mapcar #'cdr treesit-major-mode-remap-alist)))))))
+  :initialize #'custom-initialize-default
+  :set (lambda (sym val)
+         (set-default sym val)
+         (when (treesit-available-p)
+           (dolist (m treesit-major-mode-remap-alist)
+             (setq major-mode-remap-alist
+                   (if (or (eq val t) (memq (cdr m) val))
+                       (cons m major-mode-remap-alist)
+                     (delete m major-mode-remap-alist))))))
+  :version "31.1")
+
 ;;; compat-30.el ends here

modules/tools/tree-sitter/autoload/tree-sitter.el

@@ -39,6 +39,8 @@ Note that COMMIT is only available in Emacs >=31."
                    ((and (fboundp 'treesit-available-p)
                          (treesit-available-p)
                          (fboundp ts-mode)
+                         (or (eq treesit-enabled-modes t)
+                             (memq ts-mode treesit-enabled-modes))
                          ;; Only prompt once, and log other times.
                          (cl-every (if ensured?
                                        (doom-rpartial #'treesit-ready-p 'message)

modules/tools/tree-sitter/config.el

@@ -7,7 +7,32 @@
   :when (fboundp 'treesit-available-p)
   :when (treesit-available-p)
   :defer t
+  :preface
+  (setq treesit-enabled-modes t)
+
+  ;; HACK: These *-ts-mode-maybe functions all treat `treesit-enabled-modes'
+  ;;   strangely in the event the language's grammar is unavailable. Plus, they
+  ;;   add yet-another-layer of complexity for users to be cognicent of. Get rid
+  ;;   of them.
+  ;; REVIEW: Handle this during the 'doom sync' process instead.
+  (setq auto-mode-alist
+        (save-match-data
+          (cl-loop for (src . fn) in auto-mode-alist
+                   unless (and (functionp fn)
+                               (string-match "-ts-mode-maybe$" (symbol-name fn)))
+                   collect (cons src fn))))
+
   :config
+  ;; HACK: The implementation of `treesit-enabled-modes's setter and
+  ;;   `treesit-major-mode-remap-alist' are intrusively opinionated, so I
+  ;;   disable it altogether as to not unexpectedly modify
+  ;;   `major-mode-remap-alist' at runtime. What's more, there's no guarantee
+  ;;   this will be populated correctly unless the user is on a particular
+  ;;   commit of Emacs 31 or newer. Best we simply ignore it.
+  (dolist (m treesit-major-mode-remap-alist)
+    (setq major-mode-remap-alist (delete m major-mode-remap-alist)))
+  (setq treesit-major-mode-remap-alist nil)
+
   ;; HACK: treesit lacks any way to dictate where to install grammars.
   (add-to-list 'treesit-extra-load-path (concat doom-profile-data-dir "tree-sitter"))
   (defadvice! +tree-sitter--install-grammar-to-local-dir-a (fn &rest args)