`tsc-make-cursor` and `tsc-goto-xxxx` does not appear to work when created against a non-root node

[mickeynp]

I'm encountering a weird issue and I'm fairly certain it's a bug.

If you create a cursor against a non-root node the cursor movement code does not work.

Version: 0.15.1 Test case:

(ert-deftest cursor::walk-from-root-node ()
  (let ((parser (tsc-make-parser))
        (language (tree-sitter-require 'rust)))
    (tsc-set-language parser language)
    (let* ((tree (tsc-parse-string parser "fn foo() {}"))
           (root-node (tsc-root-node tree))
           (tree-sitter-tree tree)
           (cursor (tsc-make-cursor root-node)))
      (ert-info ("Moving a cursor that was made against a non-root should work")
        ;; test that the root node can navigate independently
        ;; this works
        (should (eq (tsc-node-type (tsc-current-node cursor)) 'source_file))
        (should (tsc-goto-first-child cursor))
        (should (eq (tsc-node-type (tsc-current-node cursor)) 'function_item))
        ;; this too
        (let* ((sub-node (tsc-current-node cursor))
               (sub-cursor (tsc-make-cursor sub-node)))
          (should (tsc-node-p sub-node))
          (should (tsc-cursor-p sub-cursor))
          (should (eq (tsc-node-type (tsc-current-node cursor)) 'function_item))
          ;; this should move us back from whence we came but this fails with a nil response.
          (should (tsc-goto-parent sub-cursor)))))))

EDIT: I amended the test slightly to make it more specific.

[ubolonton]

The current behavior is that tree cursor is scoped to the node it's created against. There are more details in https://github.com/tree-sitter/tree-sitter/issues/567.

[mickeynp]

Hm. Yeah, I did actually see the documentation in tree-sitter that said that, but I clearly misunderstood what they meant by that.

It's a shame as text editing with tree-sitter most often revolves around the idea of acting on/around where point is. I'll stick to the other helper methods then in the interim.

Thanks for clarifying!