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Bounded typed YAML parsing with serde-saphyr

Document status: verified. Canonical source.

Summary

serde-saphyr 1.1.0 deserializes YAML directly into Serde types. It rejects duplicate keys by default and exposes configurable resource budgets for input size, nesting, collections, anchors, aliases and parser lookahead. The crate can be compiled with only its deserialization feature. These properties fit a small, read-only metadata boundary better than the deprecated serde_yaml crate or forks that retain an unsafe LibYAML binding.

Evidence

  • The 1.1.0 release added limits for buffered comment events, simple-key lookahead and flow nesting. Locator: repository release 1.1.0, commit ad5c614, retrieved 2026-08-30.
  • The project documents conservative default budgets and incremental reader-based parsing for resource-exhaustion control. Locator: repository README.md, “Pathological inputs & budgets”, retrieved 2026-08-30.
  • Duplicate keys produce an error by default. First-wins and last-wins policies require an explicit option. Locator: repository README.md, “Duplicate keys”, retrieved 2026-08-30.
  • serde_json::Value is supported for untyped data, while direct typed deserialization rejects values that do not match the destination type. Locator: docs.rs crate page for 1.1.0, “Overview” and “Notable features”, retrieved 2026-08-30.
  • The package declares Rust edition 2024, dual MIT or Apache-2.0 licensing and independent serialize and deserialize features. Locator: docs.rs Cargo.toml.orig for 1.1.0, retrieved 2026-08-30.

Mechanism

The documentation compiler caps each source file before parsing, extracts only the initial frontmatter block and deserializes that block into a closed metadata structure. serde-saphyr applies its default syntax budgets and duplicate-key policy. File inclusion, serialization and untyped tag-driven construction are not enabled.

NUIF relevance

Borrow typed, budgeted deserialization with default duplicate-key rejection. Pin 1.1.0 with default features disabled and only deserialize enabled.

Reject YAML as a canonical NUIF interchange encoding. It is limited to repository-authored metadata for the documentation and research toolchain.

Reject serde_yaml, which is deprecated, and YAML forks backed by an unmaintained unsafe LibYAML binding. The documentation compiler does not need their serialization compatibility.

Open questions

  • Parser budget defaults require a regression fixture before metadata is accepted from untrusted pull requests at larger scale.
  • YAML 1.1 boolean inference requires quoted strings or strict options if a future metadata field accepts arbitrary scalar values.