TOML Conformance

Lanexio™ Parser supports both TOML v1.0.0 and v1.1.0 through a single package. The conformance suite validates valid input acceptance, invalid input rejection, the official toml-test corpus, a generated fuzz corpus, and real-world TOML documents (over 2,000 test files total).

Curated toml-test gate (CI)

The official toml-test reference suite is vendored-and-pinned into corpus/toml-test/ (commit bc8f2c2cca601ea91d482046ea9fef3bf7a26c28) and gated in CI by pnpm test:curated-suites (repo-level gate, see ADR 0034). The frozen ledger in corpus/toml-test/expectations.json records the bootstrap-measured baseline; it can only shrink as the parser improves, never silently grow.

268 valid .toml files, version-routed by directory (spec-1.0.0/ → TOML 1.0.0, spec-1.1.0/ and general valid → TOML 1.1.0): 268/268 clean.
511 invalid .toml files, version-routed (general invalid → TOML 1.0.0, conservative): 511/511 flagged with an error node.
Ledger: 0 expect-fail, 0 deferred at this pin. The earlier claim of 6 invalid/encoding deferrals (UTF8_LENIENCY) does not reproduce against the pinned revision: all 15 invalid/encoding files are rejected.
The .json value-decode expectations are vendored but not gated (tagged-JSON datetime encoding is a parser-feature follow-up; see ADR 0034).

The same committed corpus also powers the package harness (packages/parser-grammar-toml/src/conformance.test.ts), which previously read a gitignored copy and passed vacuously in CI. It now runs 779 real official describe-block cases.

Test results

All tests pass across six categories:

Official toml-test valid — 268 files, version-routed by spec-1.0.0 / spec-1.1.0
Official toml-test invalid — 511 files, version-routed by spec-1.0.0 / spec-1.1.0
Inline fixtures — curated valid/invalid coverage for all TOML features
Generated corpus — fuzz-generated inputs, all parse safely
Real-world documents — production TOML configs, all parse without error
Cross-version fixtures — TOML 1.1.0 constructs rejected in 1.0.0 mode (\xHH escapes, seconds-less times, inline table newlines/trailing commas)

Corrected gate: every returned tree carries metadata.language === "toml" (stamped at the single createTreeFromUint32Array call site), and the exhaustive harness reports 12,000 / 12,000 results passing (100.00%) on the corrected gate (2,000 test_files/toml files x 6 modes). TOML is byte-lossless: the lexer tiles whitespace/newline/comment/delimiter runs as trivia leaves, so emitSource(parse(x)) === x holds byte-for-byte — including a leading UTF-8 BOM (insignificant but tiled as a leaf) and CRLF line endings. Malformed bytes (e.g. bare CR or NUL) surface as TomlKind.Error leaves that still cover their byte range, so losslessness holds even on malformed input.

Version selection

parseToml(bytes) defaults to TOML v1.1.0. Use parseToml10(bytes) or parseToml11(bytes) for an explicit version. Incompatible constructs between versions are handled by the version-aware parser.

Strict mode

parseToml accepts a mode option ("lenient" or "strict"). The default is "lenient", which keeps the recovery behavior of every previous release.

In "strict" mode the parse path still never throws, and the grammar defaults to the TOML 1.0.0 rule set when no version is given. Constructs that are only valid in 1.1 are therefore rejected by rule selection:

datetimes and times without seconds (1987-07-05T17:45Z, 17:45)
inline-table newlines and trailing commas ({ abc = 123, })
\x byte escapes in basic strings ("\x33")

An explicit version always wins over the strict-mode default: parseToml(bytes, { mode: "strict", version: "1.1" }) keeps the 1.1 rule set. Rejection surfaces as LexError nodes and tree.root.hasError reads true.

Four-axis bar

Axis	Result
never-throw	0 throws across full corpus
well-formed	corpus WF = 0
lossless	corpus lossless = 0, byte-exact round-trip (corrected gate; BOM-prefixed and CRLF documents round-trip byte-for-byte, malformed bytes emit Error leaves that still cover their range)
conformance	2,000+ / 2,000+, 12,000 / 12,000 mode-results on the corrected gate

Corpus conformance

pnpm conformance:suite measured this family over the test_files/toml corpus on 2026-10-06 at Lanexio™ Parser version 1.0.0:

family	valid	invalid	raw	contract-subset	REAL-DEFECT
toml	1484	505	99.5%	100.0% (1484/1484)	0

The lower raw figure reflects the large invalid-input share (505 of 1,989 classified files); the contract-subset over the valid inputs is 100.0%.