rust-harness-policy

name	rust-harness-policy
description	Use when modifying rust-lang-project-harness Rust source, tests, policy rules, parser facts, renderers, or snapshots.

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.