How are you supposed to use the tnode/pnode rules on delimeter rule productions?

[Spartan322]

Messing around with pnodes and tnodes, I found a case where the tree will fail:

// A simple grammar for a single key-value pair.
namespace grammar
{
struct key : lexy::token_production
{
    static constexpr auto rule = dsl::quoted(-dsl::unicode::control);
};

struct integer
{
    static constexpr auto rule = dsl::digits<>;
};

struct key_value_pair
{
    static constexpr auto whitespace = dsl::ascii::space;
    static constexpr auto rule       = dsl::p<key> + dsl::lit_c<'='> + dsl::p<integer>;
};
} // namespace grammar

namespace tree_grammar
{
struct id {
    static constexpr auto rule = dsl::tnode<lexy::any_token_kind>(dsl::capture(-dsl::quoted.open()));
    static constexpr auto value = lexy::as_string<std::string>;
};

struct integer
{
    // Match the digits token and extract their integer value.
    static constexpr auto rule  = dsl::tnode<lexy::digits_token_kind>(dsl::integer<int>);
    static constexpr auto value = lexy::as_integer<int>;
};

struct key_value_pair
{
    // Skip over literal and whitespace tokens automatically.
    static constexpr auto whitespace
        = dsl::tnode<lexy::literal_token_kind> | dsl::tnode<lexy::whitespace_token_kind>;

    // Skip the key production but parse the children of the integer production.
    static constexpr auto rule = [] {
        auto key   = dsl::pnode<grammar::key>(dsl::p<id>);
        auto value = dsl::pnode<grammar::integer>;
        return key + value;
    }();

    static constexpr auto value = lexy::forward<std::string>;
};
} // namespace tree_grammar

This will parse "value" = 123 fails to parse the parse_tree_input. Is this a bug?

[NotAFlightRisk]

Not a bug, it's two things in id. The characters between the quotes become one merged token node whose kind comes from the char class you gave quoted, and -dsl::unicode::control has none, so thats lexy::unknown_token_kind (token in lexy::visualize), not any_token_kind. The rule inside tnode then has to consume that token's whole lexeme (value, no quotes), but your char class only eats one charachter. This works on v2025.05.0:

struct id {
    static constexpr auto rule = dsl::opt(dsl::tnode<lexy::unknown_token_kind>(dsl::capture(dsl::any)));
    static constexpr auto value = lexy::as_string<std::string>;
};

"value" = 123 gives value. The opt covers "", which has no content node at all. If you'd rather not match the catch-all kind, give it one with (-dsl::unicode::control).kind<my_kind::key> and lexy::parse_tree_for<Input, my_kind>.

Docs: delimited's parse tree, tnode, default token kinds.