Disallow untyped defs except in test directory

I would like to enforce type hints in the source code of a package, but not in the test code. Is there a way to use disallow_untyped_defs = true while excluding the tests directory?

Here is what I have tried:

pyproject.toml:

[tool.mypy]
disallow_untyped_defs = true
untyped_calls_exclude = ["tests"]

src/mymodule/file.py:

def hello_world() -> None:
    print("hi there!")

an empty src/mymodule/__init__.py, and tests/test_file.py:

def test_1():
    assert 1 < 2

But running mypy tests src/mymodule returns:

tests/test_file.py:1: error: Function is missing a return type annotation [no-untyped-def]
tests/test_file.py:1: note: Use "-> None" if function does not return a value
Found 1 error in 1 file (checked 3 source files)

I know I can limit the input directories by running mypy src/mymodule to limit the inputs, but I'd still like to lint the other type hinting warnings in the tests directory. I'd also like to silence the untyped-def errors raised by the VSCode Mypy Type Checker extension while developing.

Solution

You can configure mypy to silence some or all errors in any desired module. In pyproject.toml, the following will silence all mypy errors in tests folder (something I always do, since typing tests for non-library code is too pointless, but you may not want).

[tool.mypy]
disallow_untyped_defs = true

[[tool.mypy.overrides]]
ignore_errors = true
module = ["tests.*"]

The following will only allow untyped (fully or partially) declarations:

[tool.mypy]
disallow_untyped_defs = true

[[tool.mypy.overrides]]
disallow_incomplete_defs = false
disallow_untyped_defs = false
module = ["tests.*"]

You can adjust most of other configuration flags on a per-module basis in the same way.