Contributor summary: Design the smallest clear rule for choosing Python, Rust, and shared checks in one runner. Document the rule and test all three modes. (Difficulty: medium)
Context
The Python process is the runner. It executes command arrays from pyproject.toml, records exit status, and renders the existing report. Do not add a Rust runner, RustGate class, or second harness configuration file.
Today [tool.harness.settings].languages is metadata and phase checks are flat dictionaries.
Desired rule
Use check-name prefixes:
py_*: execute only when py appears in languages.rust_*: execute only when rust appears in languages.harness_*: execute in every mode; these are language-neutral checks such as forbidden-path and diff-size validation.
Exact behavior:
| languages |
execute |
["py"] |
py_* + harness_* |
["rust"] |
rust_* + harness_* |
["py", "rust"] |
py_* + rust_* + harness_* |
No command definitions are deleted when switching modes.
Compatibility question
Existing unprefixed checks must be classified: rename Python-only checks to py_*, rename language-neutral checks to harness_*, or define a narrowly scoped compatibility rule. Python-only embedded checks (for example preferences/Mutmut) must not run in Rust-only mode.
Trade-off
Prefixes preserve the current flat TOML shape and require the smallest selector change. Nested per-language tables are more explicit structurally but require more parser and report changes.
Acceptance
The three modes above are documented and tested. Human output and JSON retain the current result shape and show the configured check names.
How to contribute
Leave a short comment with your plan before coding. Keep changes focused, add or update tests, and run the checks in CONTRIBUTING.md. This is agentic developer tooling; pull requests from Python, Rust, and generalist contributors are welcome.
Contributor summary: Design the smallest clear rule for choosing Python, Rust, and shared checks in one runner. Document the rule and test all three modes. (Difficulty: medium)
Context
The Python process is the runner. It executes command arrays from
pyproject.toml, records exit status, and renders the existing report. Do not add a Rust runner, RustGate class, or second harness configuration file.Today
[tool.harness.settings].languagesis metadata and phase checks are flat dictionaries.Desired rule
Use check-name prefixes:
py_*: execute only whenpyappears inlanguages.rust_*: execute only whenrustappears inlanguages.harness_*: execute in every mode; these are language-neutral checks such as forbidden-path and diff-size validation.Exact behavior:
["py"]py_*+harness_*["rust"]rust_*+harness_*["py", "rust"]py_*+rust_*+harness_*No command definitions are deleted when switching modes.
Compatibility question
Existing unprefixed checks must be classified: rename Python-only checks to
py_*, rename language-neutral checks toharness_*, or define a narrowly scoped compatibility rule. Python-only embedded checks (for example preferences/Mutmut) must not run in Rust-only mode.Trade-off
Prefixes preserve the current flat TOML shape and require the smallest selector change. Nested per-language tables are more explicit structurally but require more parser and report changes.
Acceptance
The three modes above are documented and tested. Human output and JSON retain the current result shape and show the configured check names.
How to contribute
Leave a short comment with your plan before coding. Keep changes focused, add or update tests, and run the checks in CONTRIBUTING.md. This is agentic developer tooling; pull requests from Python, Rust, and generalist contributors are welcome.