Lets use MyPy! (please vote)

[shroominic]

MyPy is important because it adds static type checking to Python, allowing developers to catch type-related errors before runtime. By enforcing type annotations, MyPy makes code more predictable, self-documenting, and easier to understand, especially in large codebases or collaborative projects. This early error detection reduces debugging time, improves code reliability, and helps prevent subtle bugs that might otherwise go unnoticed. Additionally, MyPy can improve IDE support with better autocompletion and type hints, enhancing overall development efficiency.

[ZeeD]

FWIW I see that the code is already mildly annotated - and I also see a bunch of explicit .pyi files.
I would try to just start marking the library with a py.typed file in the package, so that the users of the library may have mypy work on it.
ATM if I run mypy on my project that uses fasthtml all I get is:

main.py:1: error: Skipping analyzing "fasthtml.components": module is installed, but missing library stubs or py.typed marker  [import-untyped]
main.py:1: note: See https://mypy.readthedocs.io/en/stable/running_mypy.html#missing-imports
main.py:3: error: Skipping analyzing "fasthtml.core": module is installed, but missing library stubs or py.typed marker  [import-untyped]
main.py:4: error: Skipping analyzing "fasthtml.fastapp": module is installed, but missing library stubs or py.typed marker  [import-untyped]
main.py:10: error: Untyped decorator makes function "get" untyped  [misc]

[shroominic]

yeah we need a py.typed