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darkwing

The terror that flaps in the night, for DuckDB.

darkwing is a hand-written, zero-dependency Go port of DuckDB v2.0's PEG-based SQL parser, built to power a first-class DuckDB engine in sqlc. See PLAN.md for the full design.

Unlike its siblings (oliphant, marino, meyer, teesql, zetajones, doubleclick), darkwing does not re-express the grammar as recursive descent: DuckDB's own production parser is an interpreter over machine-readable grammar text, so darkwing vendors the .gram/.list files verbatim and ports the engine — tokenizer, grammar loader, and matcher (with packrat memoization) — to Go.

Status

Milestones 1–6 are complete: the engine (tokenizer, grammar loader, matcher with packrat memoization), the corpus conformance gates, the full typed AST with a transformer for every statement, and the hardening pass. go test ./parser enforces, corpus-wide against the pinned DuckDB CLI:

  • Accept/reject — darkwing accepts a statement iff the pinned binary parses it (TestCorpus), including transformer-raised parser errors.
  • Error fidelity — every rejection renders the oracle's error message verbatim (TestCorpusErrorMessages), with positions pinned by unit tests.
  • Tree shape — internal/serialize output matches vendored json_serialize_sql goldens for the SELECT subset (TestSerializeGoldens), with AST snapshots covering the rest.

Hardening: FuzzParse holds the public API to its invariants on arbitrary input, benchmarks pin parse throughput and upstream's pathological-backtracking case (19 unmatched parens: milliseconds, thanks to packrat), and cmd/difftest mutates corpus seeds and diffs darkwing's verdicts against the pinned CLI (run nightly in CI while the nightly artifact matches the pin).

Next: advancing the pin to the v2.0.0 tag when it lands (milestone 7), then sqlc integration.

$ go run ./cmd/debug-parse 'SELECT 1'
$ go run ./cmd/debug-parse -tokens 'SELECT * FROM t'
$ go run ./cmd/debug-parse -ast 'FROM t SELECT x'

License

MIT (see LICENSE). Vendored DuckDB grammar files and the ported engine derive from MIT-licensed DuckDB source; see LICENSE.DUCKDB.