Add 'live' property to treesit-node-check (bug#61235)

* doc/lispref/parsing.texi (Accessing Node Information): Document.
* src/treesit.c (treesit_parser_live_p): New function.
(Ftreesit_node_check): Add 'live' property.
* test/src/treesit-tests.el (treesit-node-api): Add tests.

doc/lispref/parsing.texi

@@ -970,10 +970,15 @@ A node ``has error'' if the text it spans contains a syntax error.  It
 can be that the node itself has an error, or one of its descendants
 has an error.
 
+@cindex tree-sitter live node
+@cindex live node, tree-sitter
+A node is ``live'' if its parser is not deleted, and the buffer it
+belongs to is live.
+
 @defun treesit-node-check node property
 This function checks if @var{node} has the specified @var{property}.
 @var{property} can be @code{named}, @code{missing}, @code{extra},
-@code{outdated}, or @code{has-error}.
+@code{outdated}, @code{has-error}, or @code{live}.
 @end defun
 
 @defun treesit-node-type node

src/treesit.c

@@ -1475,6 +1475,15 @@ This symbol is the one used to create the parser.  */)
   return XTS_PARSER (parser)->language_symbol;
 }
 
+/* Return true if PARSER is not deleted and its buffer is live.  */
+static bool
+treesit_parser_live_p (Lisp_Object parser)
+{
+  CHECK_TS_PARSER (parser);
+  return ((!XTS_PARSER (parser)->deleted) &&
+	  (!NILP (Fbuffer_live_p (XTS_PARSER (parser)->buffer))));
+}
+
 /*** Parser API */
 
 DEFUN ("treesit-parser-root-node",
@@ -1908,7 +1917,8 @@ 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-PROPERTY could be `named', `missing', `extra', `outdated', or `has-error'.
+PROPERTY could be `named', `missing', `extra', `outdated',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
@@ -1924,7 +1934,10 @@ A node is "outdated" if the parser has reparsed at least once after
 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 not deleted and its buffer is
+live.  */)
   (Lisp_Object node, Lisp_Object property)
 {
   if (NILP (node)) return Qnil;
@@ -1947,9 +1960,11 @@ errors.  */)
     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 = treesit_parser_live_p (XTS_NODE (node)->parser);
   else
     signal_error ("Expecting `named', `missing', `extra', "
-		  "`outdated', or `has-error', but got",
+                  "`outdated', `has-error', or `live', but got",
 		  property);
   return result ? Qt : Qnil;
 }
@@ -3448,6 +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");

test/src/treesit-tests.el

@@ -100,6 +100,7 @@
       (should (eq nil (treesit-node-check root-node 'missing)))
       (should (eq nil (treesit-node-check root-node 'extra)))
       (should (eq nil (treesit-node-check root-node 'has-error)))
+      (should (eq t (treesit-node-check root-node 'live)))
       ;; `treesit-node-child'.
       (setq doc-node (treesit-node-child root-node 0))
       (should (equal "array" (treesit-node-type doc-node)))
@@ -160,7 +161,18 @@
                     :type 'args-out-of-range)
       ;; `treesit-node-eq'.
       (should (treesit-node-eq root-node root-node))
-      (should (not (treesit-node-eq root-node doc-node))))))
+      (should (not (treesit-node-eq root-node doc-node)))
+
+      ;; Further test for `treesit-node-check'.
+      (treesit-parser-delete parser)
+      (should (equal nil (treesit-node-check root-node 'live)))
+      ;; Recreate parser.
+      (setq parser (treesit-parser-create 'json))
+      (setq root-node (treesit-parser-root-node
+                       parser))
+      (should (equal t (treesit-node-check root-node 'live)))
+      (kill-buffer)
+      (should (equal nil (treesit-node-check root-node 'live))))))
 
 ;;; Indirect buffer