expand-mypy-coverage

name	expand-mypy-coverage
description	Use when widening mypy's checked scope beyond src/wrinklefe/__init__.py, or fixing type errors uncovered when enabling mypy on a new module. Triggers on "add types", "fix mypy", "expand mypy scope", "address mypy follow-up to

Expanding mypy coverage in wrinkleFE

Current state

• mypy config in pyproject.toml under [tool.mypy]: python_version = "3.10", warn_return_any = true, warn_unused_configs = true.
• CI only checks the package init file: .github/workflows/lint.yml runs mypy src/wrinklefe/__init__.py.
• The broader src/wrinklefe/ tree has ~102 errors today — mostly numpy Any returns and missing third-party stubs. Tracked as a follow-up to issue #87.
• Goal: walk the scope outward module-by-module until CI checks the whole package.

Workflow

1. Pick the next module to bring under mypy. Suggested order (leaves first, then aggregators):
   1. core/ (dataclasses, transforms) — least dependency surface
   2. elements/ (hex8, hex8i)
   3. failure/ (criteria modules)
   4. solver/
   5. viz/, sweep/, io/
   6. analysis.py, cli.py
   7. app.py, streamlit_viz.py (these live at repo root, not under src/)
2. Run mypy locally on just that module:

   mypy src/wrinklefe/<module>
   

3. Fix errors in this priority order:
   • Add real annotations to public functions and dataclass fields.
   • For numpy returns: prefer np.ndarray or npt.NDArray[np.float64] (import as import numpy.typing as npt) over Any.
   • For SciPy / meshio / pyvista / streamlit / plotly: install stubs if available (types-* on PyPI), otherwise add a targeted # type: ignore[import-untyped] on the import line with a comment.
   • Avoid # type: ignore without a code — always specify the error code so future widening doesn't silently hide regressions.
4. Run pytest to confirm no behavior changed.
5. Add the module to lint.yml — append it to the mypy invocation:

   mypy src/wrinklefe/__init__.py src/wrinklefe/<module>
   

   (Or switch to mypy src/wrinklefe/ once enough modules are clean.) Update the comment on lines 36-38 of lint.yml to reflect new scope.

Gotchas

• warn_return_any is on globally — any function returning a numpy operation result will trip this until annotated. Annotate the return type explicitly.
• Don't add a per-module [[tool.mypy.overrides]] section to silence whole files. The point is to fix them, not hide them. The only legitimate override is ignore_missing_imports for genuinely unstubbed third-party packages, scoped to that package only.
• The package ships a py.typed marker (see [tool.setuptools.package-data]), so downstream consumers will see our types. Sloppy Any here leaks to users.
• app.py and streamlit_viz.py are NOT under src/wrinklefe/ — they're at repo root. Adding them to the mypy invocation needs a separate path argument.

Done check

• mypy <new scope> exits clean.
• pytest passes.
• .github/workflows/lint.yml mypy invocation includes the new module.
• No new blanket ignore directives added.