Missing MISSING when the terminal is a hidden rule

[alemuller]

Code to reproduce:

module.exports = grammar({
    name: 'test',
    extras: $ => [ /\s+/ ],
    rules: {

        top: $ => repeat($.foo),

        foo: $ => seq(
            alias('(',$.open),
            $.symbol,
            alias(')',$.close)
        ),

        symbol: $ => $._word,

        // changing the rule name from `_word` to `word` it works as expected
        _word: $ => 'x',
    }
});

The aliases are not needed but they helped me to pinpoint the issue.

Test file:

()

Command:

$ tree-sitter --version
tree-sitter 0.19.4 (76862e281b3aa5d93b471bfdf903527fec4f9b29)
$ tree-sitter parse foo.test

Actual:

(top [0, 0] - [1, 0]
  (foo [0, 0] - [0, 2]
    (open [0, 0] - [0, 1])
    (symbol [0, 1] - [0, 1])
    (close [0, 1] - [0, 2])))

Expected:

(top [0, 0] - [1, 0]
  (foo [0, 0] - [0, 2]
    (open [0, 0] - [0, 1])
    (symbol [0, 1] - [0, 1])
    (close [0, 1] - [0, 2])))
test.test	0 ms	(MISSING symbol [0, 1] - [0, 1]

NOTE: Replacing _word with word in the grammar tree-sitter parse produces the correct output.

[ahlinc]

In tests it's present:

================================================================================
Missing MISSING
================================================================================

()

--------------------------------------------------------------------------------

(top
  (foo
    (open)
    (symbol
      (MISSING _word))
    (close)))

So this is a bug in CLI representation of S-expressions.

[ahlinc]

Similar to #865

[DavisVaughan]

I think this issue goes a little deeper than just the CLI representation. I have a similar situation but for me ts_node_is_missing() reports false on, for example, the symbol node from above, making it impossible to actually detect that this is a missing node.

It's doubly confusing because ts_node_has_error() will report true when called on the root node, which is correct, but then you can't find the MISSING node causing the error!