Document how to run mypy; move mypy settings to pyproject.toml

CONTRIBUTING.md

@@ -12,7 +12,7 @@ There's no particular roadmap for chap, it was created to scratch the original d
 If you're looking for a way to contribute, check out the open issues.
 If you want to discuss a possible enhancement before beginning work, opening a fresh issue is a good way to start a dialog about your idea.
 
-## Code style & linting
+## Code style & linting with pre-commit
 
 This project uses [pre-commit](https://pre-commit.com/) to maintain the code's style and perform some quality checks.
 First, install pre-commit: `pip install pre-commit`.
@@ -26,3 +26,16 @@ It is acceptable to use hints like `#  pylint: ignore=diagnostic-kind` when it's
 
 When you create a pull request, `pre-commit run --all` is run in a standardized environment, which occasionally catches things that were not seen locally.
 That green checkmark in github actions is the final arbiter of whether the code is pre-commit clean.
+
+## Type checking with mypy
+
+This project uses [mypy](https://www.mypy-lang.org/) for type-checking.
+If your system has `make`, you can type-check the project with: `make`.
+Otherwise, you need to perform several setup steps:
+ * create a virtual environment at "venv": `python -mvenv venv`
+ * install dependencies in the virtual environment: `venv/bin/pip install -r requirements.txt mypy`
+
+Then, type check with: `venv/bin/mypy`
+
+When you create a pull request, mypy is run in a standardized environment, which occasionally catches things that were not seen locally.
+That green checkmark in github actions is the final arbiter of whether the code is mypy clean.

mypy.ini

@@ -1,6 +0,0 @@
-# SPDX-FileCopyrightText: 2023 Jeff Epler <jepler@gmail.com>
-#
-# SPDX-License-Identifier: MIT
-
-[mypy]
-mypy_path = src

pyproject.toml

@@ -44,3 +44,9 @@ readme = {file = ["README.md"], content-type="text/markdown"}
 dependencies = {file = "requirements.txt"}
 [tool.setuptools.package-data]
 "pkgname" = ["py.typed"]
+[tool.mypy]
+mypy_path = ["src"]
+warn_unused_ignores = false
+warn_redundant_casts = true
+strict = true
+packages = ["chap"]