Previously, a bare child pattern in a query took whatever the next
child of the iterator was and either matched or failed: it would not
scan ahead to find a match. So `(foo ("baz"))` against a `foo` whose
implicit `child` field was `["bar", "baz"]` would fail (the pattern
took "bar" first).
Switch to forward-scan semantics: a SingleNode matcher advances through
the iterator until it finds a child that matches its sub-query. Patterns
that are named-only continue to skip past unnamed children for free.
Order is preserved across multiple bare patterns at the same level —
each pattern advances the shared iterator past whatever it consumed —
so a query cannot match children out of source order.
Captures from a failed match attempt are rolled back via a snapshot, so
partial captures from a complex sub-query do not leak across attempts.
Add two regression tests against the `do` body wrapper in a Ruby
for-loop, whose implicit `child` field contains [do, identifier, end]:
- a query for ("end") matches by skipping past `do` and the identifier
- a query for ("end") then ("do") fails, demonstrating order preservation
Three improvements to the query parser, all aimed at allowing query
patterns to refer to unnamed tokens:
1. Bare-literal capture: `"=" @op` now captures the unnamed `=` token,
matching the parenthesized form `("=") @op`. Previously the literal
branch in parse_query_list skipped the maybe_wrap_capture call, so
the `@op` was a leftover token and would error.
2. Bare `_` matches any node, named or unnamed. Previously bare `_` and
`(_)` both produced QueryNode::Any with the same matches_named_only
behaviour, so bare `_` would skip unnamed children. Now Any carries a
match_unnamed flag: false for `(_)` (named-only, tree-sitter default)
and true for bare `_` (any node).
3. Named fields and bare child patterns may be intermixed in any order.
Previously, once parse_query_fields saw a bare pattern it would stop
accepting named fields. The fix accumulates bare patterns into the
implicit `child` field and keeps parsing.
Each named field independently selects its target field for matching, so
the source-order of fields in the query is purely cosmetic and intermixing
is safe.
Add tests covering parenthesized capture, bare-literal capture, and the
named-vs-any distinction between `(_)` and bare `_`. Update query-syntax
docs to reflect all three.
Extend the desugaring config from a single flat list of rules to an
ordered sequence of named Phases. Each phase runs to completion (a
full traversal applying its rules) before the next phase starts.
Rules in different phases never compete for matches.
The config is built via the new chainable API:
DesugaringConfig::new()
.add_phase("cleanup", cleanup_rules)
.add_phase("desugar", desugar_rules)
.with_output_node_types_yaml(yaml);
Single-phase configs are just .add_phase(...) called once.
A single FreshScope is shared across phases so generated identifier
names (e.g. $tmp-N) are unique throughout the run.
Phase names appear in error messages, e.g. "Phase `desugar`:
exceeded maximum rewrite depth".
Add two regression tests: one verifying basic two-phase chained
desugaring, and one verifying that errors include the failing phase
name.
Previously, after a rule fired the engine would always re-try that
same rule on the result root. A rule whose output matched its own
query (intentionally or by accident) would loop until the global
MAX_REWRITE_DEPTH safety net kicked in.
Make the default behavior fire-once-per-node: after a rule fires on
node N, the engine no longer tries that same rule on the result root.
Other rules and child traversal are unaffected. Rules that
intentionally rewrite iteratively can opt into the old behavior via
the new Rule::repeated() builder method.
Add two regression tests using a self-swapping assignment rule:
- with .repeated(), the swap loops and trips the depth limit
- without it (default), the swap fires once and terminates
Human-friendly YAML alternative to tree-sitter node-types.json with
three sections: supertypes, named, unnamed. Supports bidirectional
conversion and building Schema objects from YAML.
Includes CLI binary (node_types_yaml) and documentation.
Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
