[DecimalTurn]

Improve parsing approach:

• Replace parallel parser-validation collections with a PathState metadata tree.
• Track table-array entry scopes within the path tree, including nested and non-contiguous headers.

[Copilot]

🟡 Changes recommended

Validation permits shared date-prototype mutation and misses parent-table conflicts that produce raw TypeErrors.

2 open issues

• Prevent prototype pollution through date-valued paths · New
• Reject array-of-tables declarations on parents with children · New

What changed in this PR

This PR centralizes semantic validation during TOML-to-JavaScript conversion in a path metadata tree, replacing parallel collections and table-scope bookkeeping.

Changes:

• Introduces PathState to track definitions and validation rules.
• Tracks array-of-tables entries separately for nested and non-contiguous headers.
• Documents the migration plan, compatibility goals, and acceptance criteria.

File	Description
src/​to-js.ts	Replaces validation collections with path-based metadata and per-entry scopes.
docs/​PLAN-Parser-Validation-State.md	Documents the design, migration steps, and validation requirements.

_{Review effort: Balanced}

[github-actions]

Benchmark comparison

This branch measured against latest in one run on the same runner.
Ratios close to 1.0 are within run to run noise.

Fixture Benchmark Results

Time per iteration. Lower is better.

Parse, smol-toml spec example (toml-spec-example.toml)

	Library	Performance	Slowdown	Ratio
🥇	smol-toml@1.9.1 (Date)	8.22 µs/iter	1x
🥈	smol-toml@1.9.1 (Temporal)	11.38 µs/iter	1.38x
🥉	@iarna/toml@3.0.0	21.52 µs/iter	2.62x
4	@decimalturn/toml-patch@3.3.1 (Date, current)	31.84 µs/iter	3.87x	1.17
5	@decimalturn/toml-patch@3.3.1 (baseline)	37.28 µs/iter	4.53x
6	@decimalturn/toml-patch@3.3.1 (Temporal, current)	39.31 µs/iter	4.78x

Parse, smol-toml 5MB mixed (5mb-mixed.toml)

	Library	Performance	Slowdown	Ratio
🥇	smol-toml@1.9.1 (Date)	74.78 ms/iter	1x
🥈	smol-toml@1.9.1 (Temporal)	194.22 ms/iter	2.60x
🥉	@decimalturn/toml-patch@3.3.1 (Date, current)	327.32 ms/iter	4.38x	1.08
4	@decimalturn/toml-patch@3.3.1 (baseline)	352.49 ms/iter	4.71x
5	@decimalturn/toml-patch@3.3.1 (Temporal, current)	506.52 ms/iter	6.77x
-	@iarna/toml@3.0.0	DNF	DNF

Parse, iarna spec example v0.4.0 (0A-spec-01-example-v0.4.0.toml)

	Library	Performance	Slowdown	Ratio
🥇	smol-toml@1.9.1 (Date)	47.16 µs/iter	1x
🥈	smol-toml@1.9.1 (Temporal)	58.17 µs/iter	1.23x
🥉	@iarna/toml@3.0.0	136.25 µs/iter	2.89x
4	@decimalturn/toml-patch@3.3.1 (Date, current)	181.79 µs/iter	3.85x	1.18
5	@decimalturn/toml-patch@3.3.1 (Temporal, current)	206.51 µs/iter	4.38x
6	@decimalturn/toml-patch@3.3.1 (baseline)	214.23 µs/iter	4.54x

Stringify, smol-toml spec example (toml-spec-example.toml)

	Library	Performance	Slowdown	Ratio
🥇	smol-toml@1.9.1	5.53 µs/iter	1x
🥈	@iarna/toml@3.0.0	18.38 µs/iter	3.32x
🥉	@decimalturn/toml-patch@3.3.1 (baseline)	96.43 µs/iter	17.43x
4	@decimalturn/toml-patch@3.3.1 (current)	96.99 µs/iter	17.53x	0.99

Stringify, smol-toml 5MB mixed (5mb-mixed.toml)

	Library	Performance	Slowdown	Ratio
🥇	smol-toml@1.9.1	68.90 ms/iter	1x
🥈	@iarna/toml@3.0.0	238.45 ms/iter	3.46x
🥉	@decimalturn/toml-patch@3.3.1 (baseline)	792.50 ms/iter	11.50x
4	@decimalturn/toml-patch@3.3.1 (current)	819.38 ms/iter	11.89x	0.97

Stringify, iarna spec example v0.4.0 (0A-spec-01-example-v0.4.0.toml)

	Library	Performance	Slowdown	Ratio
🥇	smol-toml@1.9.1	23.69 µs/iter	1x
🥈	@iarna/toml@3.0.0	81.27 µs/iter	3.43x
🥉	@decimalturn/toml-patch@3.3.1 (baseline)	450.99 µs/iter	19.03x
4	@decimalturn/toml-patch@3.3.1 (current)	468.18 µs/iter	19.76x	0.96