Rust Harness Policy

Rust Harness Policy

Use this skill when onboarding to this repository or when compact harness output does not give enough context to repair src/ or tests/ Rust code directly. Do not reread it on every run after the relevant code-level policy and skill bindings are configured.

Operating Contract

• Treat the native Rust parser as the fact layer. New policy behavior must consume parser/discovery facts, not raw string scans or ad hoc file lists.
• Do not compete with rustc, rustfmt, or Clippy. Harness policy covers LLM/Agent structural risk: owner drift, module shape, unclear edit surfaces, special-file bloat, oversized files, unclear dependency paths, compact repair output, and verification obligations.
• Keep compact text Agent-facing. Avoid human audit headers such as package counts, file counts, parsed counts, source-root summaries, empty sections, and success prose. Clean compact output should stay minimal.
• Keep src/ and tests/ fully inside harness self-apply. A policy change that would let cargo test or cargo test --lib escape the harness is a regression.
• Prefer owner-level APIs and crate::... paths over broad scope imports. super::super and broad glob imports are structural clarity risks for this repository even when Rust permits them.
• Keep medium or complex work folder-first. If a file starts collecting several unrelated responsibilities, split by parser, rule, renderer, profile, fixture, or snapshot ownership.
• Every new policy shape needs focused tests and, where compact text changes, an insta snapshot.

Parser-First Checklist

• Add or extend parser facts first.
• Deduplicate facts at the parser/discovery boundary when the policy would otherwise need local deduplication.
• Preserve line numbers and test-context metadata when diagnostics or policies depend on them.
• Let rules ask precise questions of the fact model instead of rediscovering path or syntax relationships.

Validation

Run the repository validation set before committing code changes:

direnv exec . cargo test
direnv exec . cargo fmt --check
direnv exec . cargo clippy --all-targets -- -D warnings
git diff --check

For docs-only skill updates, git diff --check is the minimum. If the update changes executable examples or validation instructions, run the full set.

GitHub Actions should be checked for Ubuntu and Windows. A pending macOS check can be ignored while the project account has no macOS Actions quota.