bug#61235: 30.0.50; tree-sit: `treesit-node-check' lacks a way to tell if a node belongs to a deleted parser

[Yuan Fu <casouri@gmail.com>]

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Mickey Petersen <mickey@masteringemacs.org> writes:

> There's no way to tell if a node belongs to a now-deleted
> parser. Checking if it is `missing' or `outdated' returns nil; there
> is no way to ascertain this state except by catching an error if you
> try to get its node text, type, etc.

That sounds reasonable. I can add treesit-parser-live-p, and add
a "live" PROPERTY to treesit-node-check.

treesit-parser-live-p only returns t when the parser is not deleted AND
its buffer is live. I assume that’s more useful than just checking
whether the parser is deleted, for whatever usecase you have?

Eli, should we add this in the release branch or Emacs 30? This
functionality is possible to implement in Elisp, albeit a bit clunky. I
attached a patch of how would it look like (without documentation/test).

Yuan


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From 9d7651bb7b97faff034186a2667d90e42f6f9e5b Mon Sep 17 00:00:00 2001
From: Yuan Fu <casouri@gmail.com>
Date: Sun, 5 Feb 2023 20:22:52 -0800
Subject: [PATCH] Demo

---
 src/treesit.c | 27 ++++++++++++++++++++++++---
 1 file changed, 24 insertions(+), 3 deletions(-)

diff --git a/src/treesit.c b/src/treesit.c
index 8e772523cc7..94c523950d1 100644
--- a/src/treesit.c
+++ b/src/treesit.c
@@ -1471,6 +1471,20 @@ DEFUN ("treesit-parser-language",
   return XTS_PARSER (parser)->language_symbol;
 }
 
+DEFUN ("treesit-parser-live-p",
+       Ftreesit_parser_live_p, Streesit_parser_live_p, 1, 1, 0,
+       doc: /* Check whether PARSER is not deleted and its buffer is live.  */)
+  (Lisp_Object parser)
+{
+  treesit_check_parser (parser);
+  if (XTS_PARSER (parser)->deleted)
+    return Qnil;
+  else if (NILP (Fbuffer_live_p (XTS_PARSER (parser)->buffer)))
+    return Qnil;
+  else
+    return Qt;
+}
+
 /*** Parser API */
 
 DEFUN ("treesit-parser-root-node",
@@ -1904,7 +1918,8 @@ DEFUN ("treesit-node-check",
        Ftreesit_node_check, Streesit_node_check, 2, 2, 0,
        doc: /* Return non-nil if NODE has PROPERTY, nil otherwise.
 
-PROPERTY could be `named', `missing', `extra', `outdated', or `has-error'.
+PROPERTY could be `named', `missing', `extra', `outdated',
+`has-error', or `live'.
 
 Named nodes correspond to named rules in the language definition,
 whereas "anonymous" nodes correspond to string literals in the
@@ -1920,7 +1935,9 @@ DEFUN ("treesit-node-check",
 the node was created.
 
 A node "has error" if itself is a syntax error or contains any syntax
-errors.  */)
+errors.
+
+A node is "live" if its parser is live (i.e., not deleted).  */)
   (Lisp_Object node, Lisp_Object property)
 {
   if (NILP (node)) return Qnil;
@@ -1943,9 +1960,11 @@ DEFUN ("treesit-node-check",
     result = ts_node_is_extra (treesit_node);
   else if (EQ (property, Qhas_error))
     result = ts_node_has_error (treesit_node);
+  else if (EQ (property, Qlive))
+    result = Ftreesit_parser_live_p (XTS_NODE (node)->parser);
   else
     signal_error ("Expecting `named', `missing', `extra', "
-		  "`outdated', or `has-error', but got",
+                  "`outdated', `has-error', or `deleted', but got",
 		  property);
   return result ? Qt : Qnil;
 }
@@ -3444,6 +3463,7 @@ syms_of_treesit (void)
   DEFSYM (Qextra, "extra");
   DEFSYM (Qoutdated, "outdated");
   DEFSYM (Qhas_error, "has-error");
+  DEFSYM (Qlive, "live");
 
   DEFSYM (QCanchor, ":anchor");
   DEFSYM (QCequal, ":equal");
@@ -3577,6 +3597,7 @@ syms_of_treesit (void)
   defsubr (&Streesit_parser_list);
   defsubr (&Streesit_parser_buffer);
   defsubr (&Streesit_parser_language);
+  defsubr (&Streesit_parser_live_p);
 
   defsubr (&Streesit_parser_root_node);
   /* defsubr (&Streesit_parse_string); */
-- 
2.33.1