fix(emacs-tree-sitter-move): get named parents & check for nils

If there was no parent, the while loop would try to get the parent of
a `nil`, which crashes and burns.

We now also ignore any non-named parents; this might be unnecessary,
if tree-sitter parent nodes are always named, but I don’t know that at
the moment and it’s not documented very well, so better safe than
sorry.

Change-Id: Ia72ee9241b885ab312f8ecf7a8fbfece7eea8f1b
Reviewed-on: https://cl.tvl.fyi/c/depot/+/2263
Reviewed-by: Profpatsch <mail@profpatsch.de>
Tested-by: BuildkiteCI

users/Profpatsch/emacs-tree-sitter-move/tree-sitter-move.el

@@ -50,19 +50,27 @@
     (tsc-get-named-descendant-for-position-range
      (tsc-root-node tree-sitter-tree) p p)))
 
+;; TODO: is this function necessary?
+;; Maybe tree-sitter always guarantees that parents are named?
+(defun tsc-get-named-parent (node)
+  (when-let ((parent (tsc-get-parent node)))
+    (while (and parent (not (tsc-node-named-p parent)))
+      (setq parent (tsc-get-parent parent)))
+    parent))
+
 (defun tsc-get-first-named-node-with-siblings-up (node)
   "Returns the first 'upwards' node that has siblings. That includes the current
   node, so if the given node has siblings, it is returned. Returns nil if there
   is no such node until the root"
   (when-let ((has-siblings-p
-            (lambda (parent-node)
-              (> (tsc-count-named-children parent-node)
-                 1)))
-           (cur node)
-           (parent (tsc-get-parent node)))
-      (while (not (funcall has-siblings-p parent))
-        (setq cur parent)
-        (setq parent (tsc-get-parent cur)))
+              (lambda (parent-node)
+                (> (tsc-count-named-children parent-node)
+                   1)))
+             (cur node)
+             (parent (tsc-get-named-parent node)))
+    (while (and parent (not (funcall has-siblings-p parent)))
+      (setq cur parent)
+      (setq parent (tsc-get-named-parent cur)))
     cur))
 
 (defun tree-sitter-move--set-cursor-to-node (node)