Add improved static type checking in setup.py

[kibablu]

Add static type checking on setup.py with Any as the path-like object is either str or bytes object representing a path, or an object implementing the os path.

[callahad]

Unfortunately, declaring Any doesn't help us catch invalid values. For example, this function would throw an exception if passed an integer, but mypy wouldn't warn us ahead of time since everything matches Any.

What do you think these types should be?

[kibablu]

I was thinking of str but we also have bytes objects representing a path, is it possible to combine str and bytes

[callahad]

It is :) https://docs.python.org/3/library/typing.html#typing.Union

[callahad]

I'm surprised this is failing.

Let me test if I can get this to blow up locally, and if so, whether adding from __future__ import annotations fixes it or if there's something else we need to do.

[callahad]

Okay, yep. This is failing for a very obscure reason. Python 3.7 and 3.8 don't understand the [str] part of PathLike[str], and so they throw an error.

We can fix that by opting into new behaviors for type annotations. Making the following change should get the tests to pass:

diff --git a/setup.py b/setup.py
index 88a79f5..2e91d7a 100755
--- a/setup.py
+++ b/setup.py
@@ -16,9 +16,11 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-from typing import Union
-from os import PathLike
+from __future__ import annotations
+
 import os.path
+from os import PathLike
+from typing import Union
 
 from setuptools import find_packages, setup
 

...and since we're using the __future__ import, we can also use the new shorthand syntax for Unions:

diff --git a/setup.py b/setup.py
index 2e91d7a..303c791 100755
--- a/setup.py
+++ b/setup.py
@@ -20,7 +20,6 @@ from __future__ import annotations
 
 import os.path
 from os import PathLike
-from typing import Union
 
 from setuptools import find_packages, setup
 
@@ -29,7 +28,7 @@ from setuptools import find_packages, setup
 # Used for the long_description.  It's nice, because now 1) we have a top level
 # README file and 2) it's easier to type in the README file than to put a raw
 # string in below ...
-def read(fname: Union[str, PathLike[str]]) -> str:
+def read(fname: str | PathLike[str]) -> str:
     return open(os.path.join(os.path.dirname(__file__), fname)).read()
 
 

[kibablu]

Thank you @callahad 😃 🎉 🎉

[callahad]

And the tests pass! Yay! Thank you so much