Change treesit-parser-list from variable to function

Effectively making the list internal.  Now Emacs user cannot shoot
themselves in the foot by removing a parser from the list, make
chaanges to buffer and add that parser back to the list.

* doc/lispref/parsing.texi (Language Definitions, Using Parser)
(Retrieving Node, Multiple Languages): Change variable to function.
* lisp/treesit.el (treesit-language-at, treesit-node-on)
(treesit-buffer-root-node, treesit-indent, treesit-check-indent)
(treesit-search-forward, treesit-search-beginning)
(treesit-end-of-defun, treesit-inspect-mode): Change variable to
function.
* src/buffer.c (bset_ts_parser_list, reset_buffer, init_buffer_once):
Add ts_parser_list.
* src/buffer.h (struct buffer): Add ts_parser_list.
* src/treesit.c (ts_record_change, Ftreesit_parser_create): Use the
buffer field instead of the old buffer local variable.
(Ftreesit_parser_delete, Ftreesit_parser_list): New functions.
(syms_of_treesit): Remove treesit-parser-list.
* test/src/treesit-tests.el (treesit-basic-parsing): Use the new
function.

6 files changed, 107 insertions, 51 deletions

diff --git a/doc/lispref/parsing.texi b/doc/lispref/parsing.texi
index b077f557432..27755e0caa5 100644
--- a/doc/lispref/parsing.texi
+++ b/doc/lispref/parsing.texi
@@ -184,7 +184,7 @@ of a node, then the mode-line only displays the smallest node that
 spans point, and its immediate parent.
 
 This minor mode doesn't create parsers on its own.  It simply uses the
-first parser in @var{treesit-parser-list} (@pxref{Using Parser}).
+first parser in @code{(treesit-parser-list)} (@pxref{Using Parser}).
 @end deffn
 
 @heading Reading the grammar definition
@@ -407,15 +407,19 @@ Tree-sitter can only handle buffer no larger than about 4GB.  If the
 size exceeds that, Emacs signals @var{treesit-buffer-too-large}
 with signal data being the buffer size.
 
-@vindex treesit-parser-list
 Once a parser is created, Emacs automatically adds it to the
-buffer-local variable @var{treesit-parser-list}.  Every time a
-change is made to the buffer, Emacs updates parsers in this list so
-they can update their syntax tree incrementally.  Therefore, one must
-not remove parsers from this list and put the parser back in: if any
-change is made when that parser is absent, the parser will be
-permanently out-of-sync with the buffer content, and shouldn't be used
-anymore.
+buffer-local parser list.  Every time a change is made to the buffer,
+Emacs updates parsers in this list so they can update their syntax
+tree incrementally.
+
+@defun treesit-parser-list &optional buffer
+This function returns the parser list of @var{buffer}.  And
+@var{buffer} defaults to the current buffer.
+@end defun
+
+@defun treesit-parser-delete parser
+This function deletes @var{parser}.
+@end defun
 
 @cindex tree-sitter narrowing
 @anchor{tree-sitter narrowing} Normally, a parser ``sees'' the whole
@@ -477,10 +481,10 @@ the @var{point}.  In other words, the start of the node is equal or
 greater than @var{point}.
 
 When @var{parser-or-lang} is nil, this function uses the first parser
-in @var{treesit-parser-list} in the current buffer.  If
+in @code{(treesit-parser-list)} in the current buffer.  If
 @var{parser-or-lang} is a parser object, it use that parser; if
 @var{parser-or-lang} is a language, it finds the first parser using
-that language in @var{treesit-parser-list} and use that.
+that language in @code{(treesit-parser-list)} and use that.
 
 If @var{named} is non-nil, this function looks for a named node
 instead (@pxref{tree-sitter named node, named node}).
@@ -507,10 +511,10 @@ smallest node that covers that empty line.  You probably want to use
 @code{treesit-node-at} instead.
 
 When @var{parser-or-lang} is nil, this function uses the first parser
-in @var{treesit-parser-list} in the current buffer.  If
+in @code{(treesit-parser-list)} in the current buffer.  If
 @var{parser-or-lang} is a parser object, it use that parser; if
 @var{parser-or-lang} is a language, it finds the first parser using
-that language in @var{treesit-parser-list} and use that.
+that language in @code{(treesit-parser-list)} and use that.
 
 If @var{named} is non-nil, this function looks for a named node
 instead (@pxref{tree-sitter named node, named node}).
@@ -523,7 +527,7 @@ This function returns the root node of the syntax tree generated by
 
 @defun treesit-buffer-root-node &optional language
 This function finds the first parser that uses @var{language} in
-@var{treesit-parser-list} in the current buffer, and returns the
+@code{(treesit-parser-list)} in the current buffer, and returns the
 root node of that buffer.  If it cannot find an appropriate parser, it
 returns nil.
 @end defun
@@ -1267,7 +1271,7 @@ Like @code{treesit-parser-set-included-ranges}, this function sets
 the ranges of @var{parser-or-lang} to @var{ranges}.  Conveniently,
 @var{parser-or-lang} could be either a parser or a language.  If it is
 a language, this function looks for the first parser in
-@var{treesit-parser-list} for that language in the current buffer,
+@code{(treesit-parser-list)} for that language in the current buffer,
 and set range for it.
 @end defun
 
@@ -1301,7 +1305,7 @@ Like other query functions, this function raises an
 @defun treesit-language-at point
 This function tries to figure out which language is responsible for
 the text at @var{point}.  It goes over each parser in
-@var{treesit-parser-list} and see if that parser's range covers
+@code{(treesit-parser-list)} and see if that parser's range covers
 @var{point}.
 @end defun
 
diff --git a/lisp/treesit.el b/lisp/treesit.el
index 5b65e00e078..3cfafd0d156 100644
--- a/lisp/treesit.el
+++ b/lisp/treesit.el
@@ -75,7 +75,7 @@ Return the root node of the syntax tree."
 
 (defun treesit-language-at (point)
   "Return the language used at POINT."
-  (cl-loop for parser in treesit-parser-list
+  (cl-loop for parser in (treesit-parser-list)
            if (treesit-node-on point point parser)
            return (treesit-parser-language parser)))
 
@@ -122,7 +122,7 @@ greater or larger than POINT.  Return nil if none find.  If NAMED
 non-nil, only look for named node.
 
 If PARSER-OR-LANG is nil, use the first parser in
-`treesit-parser-list'; if PARSER-OR-LANG is a parser, use
+(`treesit-parser-list'); if PARSER-OR-LANG is a parser, use
 that parser; if PARSER-OR-LANG is a language, find a parser using
 that language in the current buffer, and use that."
   (let ((node (if (treesit-parser-p parser-or-lang)
@@ -150,7 +150,7 @@ Return nil if none find.  If NAMED non-nil, only look for named
 node.
 
 If PARSER-OR-LANG is nil, use the first parser in
-`treesit-parser-list'; if PARSER-OR-LANG is a parser, use
+(`treesit-parser-list'); if PARSER-OR-LANG is a parser, use
 that parser; if PARSER-OR-LANG is a language, find a parser using
 that language in the current buffer, and use that."
   (let ((root (if (treesit-parser-p parser-or-lang)
@@ -160,13 +160,13 @@ that language in the current buffer, and use that."
 
 (defun treesit-buffer-root-node (&optional language)
   "Return the root node of the current buffer.
-Use the first parser in `treesit-parser-list', if LANGUAGE is
+Use the first parser in (`treesit-parser-list'), if LANGUAGE is
 non-nil, use the first parser for LANGUAGE."
   (if-let ((parser
             (or (if language
                     (or (treesit-parser-create language)
                         (error "Cannot find a parser for %s" language))
-                  (or (car treesit-parser-list)
+                  (or (car (treesit-parser-list))
                       (error "Buffer has no parser"))))))
       (treesit-parser-root-node parser)))
 
@@ -770,7 +770,7 @@ of the current line.")
                 (skip-chars-forward " \t")
                 (point)))
          (smallest-node
-          (cl-loop for parser in treesit-parser-list
+          (cl-loop for parser in (treesit-parser-list)
                    for node = (treesit-node-at bol parser)
                    if node return node))
          (node (treesit-parent-while
@@ -856,7 +856,7 @@ This is a more primitive function, you might want to use
 
 QUERY has to capture the node to match.  LANG specifies the
 language in which we search for nodes.  If LANG is nil, use the
-first parser in `treesit-parser-list'.
+first parser in (`treesit-parser-list').
 
 Move forward/backward ARG times, positive ARG means go forward,
 negative ARG means go backward.
@@ -875,7 +875,7 @@ the tree."
   (cl-loop for idx from 1 to (abs arg)
            for parser = (if lang
                             (treesit-parser-create lang)
-                          (car treesit-parser-list))
+                          (car (treesit-parser-list)))
            for node =
            (if-let ((starting-point (point))
                     (node (treesit-node-at (point) parser t)))
@@ -914,7 +914,7 @@ Stops at the beginning of matched node.
 
 QUERY has to capture the node to match.  LANG specifies the
 language in which we search for nodes.  If LANG is nil, use the
-first parser in `treesit-parser-list'.
+first parser in (`treesit-parser-list').
 
 Move forward/backward ARG times, positive ARG means go forward,
 negative ARG means go backward.
@@ -937,7 +937,7 @@ Stops at the end of matched node.
 
 QUERY has to capture the node to match.  LANG specifies the
 language in which we search for nodes.  If LANG is nil, use the
-first parser in `treesit-parser-list'.
+first parser in (`treesit-parser-list').
 
 Move forward/backward ARG times, positive ARG means go forward,
 negative ARG means go backward.
@@ -993,7 +993,7 @@ ARGth preceding end of defun.  Defun is defined according to
 If called interactively, show in echo area, otherwise set
 `treesit--inspect-name' (which will appear in the mode-line
 if `treesit-inspect-mode' is enabled).  Uses the first parser
-in `treesit-parser-list'."
+in (`treesit-parser-list')."
   (interactive "p")
   ;; NODE-LIST contains all the node that starts at point.
   (let* ((node-list
@@ -1053,7 +1053,7 @@ node, then we just display the smallest node that spans point and
 its immediate parent.
 
 This minor mode doesn't create parsers on its own.  It simply
-uses the first parser in `treesit-parser-list'."
+uses the first parser in (`treesit-parser-list')."
   :lighter nil
   (if treesit-inspect-mode
       (progn
diff --git a/src/buffer.c b/src/buffer.c
index a0761f5b59a..97e9e227386 100644
--- a/src/buffer.c
+++ b/src/buffer.c
@@ -231,6 +231,13 @@ bset_extra_line_spacing (struct buffer *b, Lisp_Object val)
 {
   b->extra_line_spacing_ = val;
 }
+#ifdef HAVE_TREE_SITTER
+static void
+bset_ts_parser_list (struct buffer *b, Lisp_Object val)
+{
+  b->ts_parser_list_ = val;
+}
+#endif
 static void
 bset_file_format (struct buffer *b, Lisp_Object val)
 {
@@ -1004,6 +1011,9 @@ reset_buffer (register struct buffer *b)
     (b, BVAR (&buffer_defaults, enable_multibyte_characters));
   bset_cursor_type (b, BVAR (&buffer_defaults, cursor_type));
   bset_extra_line_spacing (b, BVAR (&buffer_defaults, extra_line_spacing));
+#ifdef HAVE_TREE_SITTER
+  bset_ts_parser_list (b, Qnil);
+#endif
 
   b->display_error_modiff = 0;
 }
@@ -5273,6 +5283,9 @@ init_buffer_once (void)
   XSETFASTINT (BVAR (&buffer_local_flags, tab_line_format), idx); ++idx;
   XSETFASTINT (BVAR (&buffer_local_flags, cursor_type), idx); ++idx;
   XSETFASTINT (BVAR (&buffer_local_flags, extra_line_spacing), idx); ++idx;
+#ifdef HAVE_TREE_SITTER
+  XSETFASTINT (BVAR (&buffer_local_flags, ts_parser_list), idx); ++idx;
+#endif
   XSETFASTINT (BVAR (&buffer_local_flags, cursor_in_non_selected_windows), idx); ++idx;
 
   /* buffer_local_flags contains no pointers, so it's safe to treat it
@@ -5343,6 +5356,9 @@ init_buffer_once (void)
   bset_bidi_paragraph_separate_re (&buffer_defaults, Qnil);
   bset_cursor_type (&buffer_defaults, Qt);
   bset_extra_line_spacing (&buffer_defaults, Qnil);
+#ifdef HAVE_TREE_SITTER
+  bset_ts_parser_list (&buffer_defaults, Qnil);
+#endif
   bset_cursor_in_non_selected_windows (&buffer_defaults, Qt);
 
   bset_enable_multibyte_characters (&buffer_defaults, Qt);
diff --git a/src/buffer.h b/src/buffer.h
index 135eaf72d30..bc07a63b537 100644
--- a/src/buffer.h
+++ b/src/buffer.h
@@ -561,6 +561,10 @@ struct buffer
      in the display of this buffer.  */
   Lisp_Object extra_line_spacing_;
 
+#ifdef HAVE_TREE_SITTER
+  /* A list of tree-sitter parsers for this buffer.  */
+  Lisp_Object ts_parser_list_;
+#endif
   /* Cursor type to display in non-selected windows.
      t means to use hollow box cursor.
      See `cursor-type' for other values.  */
diff --git a/src/treesit.c b/src/treesit.c
index fcb333b8ec4..be0955805cc 100644
--- a/src/treesit.c
+++ b/src/treesit.c
@@ -342,8 +342,8 @@ void
 ts_record_change (ptrdiff_t start_byte, ptrdiff_t old_end_byte,
                   ptrdiff_t new_end_byte)
 {
-  for (Lisp_Object parser_list =
-         Fsymbol_value (Qtreesit_parser_list);
+  for (Lisp_Object parser_list
+         = BVAR (current_buffer, ts_parser_list);
        !NILP (parser_list);
        parser_list = XCDR (parser_list))
     {
@@ -704,23 +704,24 @@ parser.  If NO-REUSE is non-nil, always create a new parser.  */)
   ts_initialize ();
 
   CHECK_SYMBOL (language);
-  struct buffer *old_buffer = current_buffer;
-  if (!NILP (buffer))
+  struct buffer *buf;
+  if (NILP (buffer))
+    buf = current_buffer;
+  else
     {
       CHECK_BUFFER (buffer);
-      set_buffer_internal (XBUFFER (buffer));
+      buf = XBUFFER (buffer);
     }
-  ts_check_buffer_size (current_buffer);
+  ts_check_buffer_size (buf);
 
   /* See if we can reuse a parser.  */
-  for (Lisp_Object tail = Fsymbol_value (Qtreesit_parser_list);
+  for (Lisp_Object tail = BVAR (buf, ts_parser_list);
        NILP (no_reuse) && !NILP (tail);
        tail = XCDR (tail))
     {
       struct Lisp_TS_Parser *parser = XTS_PARSER (XCAR (tail));
       if (EQ (parser->language_symbol, language))
         {
-          set_buffer_internal (old_buffer);
           return XCAR (tail);
         }
     }
@@ -734,13 +735,53 @@ parser.  If NO-REUSE is non-nil, always create a new parser.  */)
   Lisp_Object lisp_parser
     = make_ts_parser (Fcurrent_buffer (), parser, NULL, language);
 
-  Fset (Qtreesit_parser_list,
-        Fcons (lisp_parser, Fsymbol_value (Qtreesit_parser_list)));
+  BVAR (buf, ts_parser_list)
+    = Fcons (lisp_parser, BVAR (buf, ts_parser_list));
 
-  set_buffer_internal (old_buffer);
   return lisp_parser;
 }
 
+DEFUN ("treesit-parser-delete",
+       Ftreesit_parser_delete, Streesit_parser_delete,
+       1, 1, 0,
+       doc: /* Delete PARSER from its buffer.  */)
+  (Lisp_Object parser)
+{
+  CHECK_TS_PARSER (parser);
+  Lisp_Object buffer = XTS_PARSER (parser)->buffer;
+  struct buffer *buf = XBUFFER (buffer);
+  BVAR (buf, ts_parser_list)
+    = Fdelete (parser, BVAR (buf, ts_parser_list));
+  return Qnil;
+}
+
+DEFUN ("treesit-parser-list",
+       Ftreesit_parser_list, Streesit_parser_list,
+       0, 1, 0,
+       doc: /* Return BUFFER's parser list.
+BUFFER defaults to the current buffer.  */)
+  (Lisp_Object buffer)
+{
+  struct buffer *buf;
+  if (NILP (buffer))
+    buf = current_buffer;
+  else
+    {
+      CHECK_BUFFER (buffer);
+      buf = XBUFFER (buffer);
+    }
+  /* Return a fresh list so messing with that list doesn't affect our
+     internal data.  */
+  Lisp_Object return_list = Qnil;
+  for (Lisp_Object tail = BVAR (buf, ts_parser_list);
+       !NILP (tail);
+       tail = XCDR (tail))
+    {
+      return_list = Fcons (XCAR (tail), return_list);
+    }
+  return Freverse (return_list);
+}
+
 DEFUN ("treesit-parser-buffer",
        Ftreesit_parser_buffer, Streesit_parser_buffer,
        1, 1, 0,
@@ -1799,17 +1840,6 @@ syms_of_treesit (void)
                 "This node is outdated, please retrieve a new one",
                 Qtreesit_error);
 
-  DEFSYM (Qtreesit_parser_list, "treesit-parser-list");
-  DEFVAR_LISP ("treesit-parser-list", Vtreesit_parser_list,
-               doc: /* A list of tree-sitter parsers.
-
-If you removed a parser from this list, do not put it back in.  Emacs
-keeps the parser in this list updated with any change in the buffer.
-If removed and put back in, there is no guarantee that the parser is in
-sync with the buffer's content.  */);
-  Vtreesit_parser_list = Qnil;
-  Fmake_variable_buffer_local (Qtreesit_parser_list);
-
   DEFVAR_LISP ("treesit-load-name-override-list",
                Vtreesit_load_name_override_list,
                doc:
@@ -1848,6 +1878,8 @@ dynamic libraries, in that order.  */);
   defsubr (&Streesit_node_parser);
 
   defsubr (&Streesit_parser_create);
+  defsubr (&Streesit_parser_delete);
+  defsubr (&Streesit_parser_list);
   defsubr (&Streesit_parser_buffer);
   defsubr (&Streesit_parser_language);
 
diff --git a/test/src/treesit-tests.el b/test/src/treesit-tests.el
index 416329d94dd..ebfe650dc08 100644
--- a/test/src/treesit-tests.el
+++ b/test/src/treesit-tests.el
@@ -27,7 +27,7 @@
   (with-temp-buffer
     (let ((parser (treesit-parser-create 'json)))
       (should
-       (eq parser (car treesit-parser-list)))
+       (eq parser (car (treesit-parser-list))))
       (should
        (equal (treesit-node-string
                (treesit-parser-root-node parser))