Improve `sys` stubs by AlexWaygood · Pull Request #6816 · python/typeshed

AlexWaygood · 2022-01-04T18:12:28Z

There are quite a few errors in the stubs for the sys module. Most of these appear to have slipped through the net due to the fact that stubtest isn't much good for this module.

For example, take the sys.flags object. In typeshed, we type it like this:

class _flags:
    # rest of the class definition here

flags: _flags

But at runtime, it actually looks like this:

>>> import sys
>>> sys.flags
sys.flags(debug=0, inspect=0, interactive=0, optimize=0, dont_write_bytecode=0, no_user_site=0, no_site=0, ignore_environment=0, verbose=0, bytes_warning=0, quiet=0, hash_randomization=1, isolated=0, dev_mode=False, utf8_mode=0)
>>> type(sys.flags)
<class 'sys.flags'>

Yup, that's a variable that has the same name as the class it's an instance of. As a result of this sys-module magic, stubtest just hasn't been checking the following documented attributes in sys:

sys.flags
sys.version_info
sys.float_info
sys.hash_info
sys.int_info
The return type of sys.getwindowsversion()
The return type of sys.get_asyncgen_hooks()

Akuli · 2022-01-04T21:02:44Z

 if sys.platform == "win32":
+    # A tuple of length 5, even though it has more than 5 attributes.
+    @final
+    class _WinVersion(_uninstantiable_structseq, tuple[int, int, int, int, str]):
+        @property
+        def major(self) -> int: ...
+        @property
+        def minor(self) -> int: ...
+        @property
+        def build(self) -> int: ...
+        @property
+        def platform(self) -> int: ...
+        @property
+        def service_pack(self) -> str: ...
+        @property
+        def service_pack_minor(self) -> int: ...
+        @property
+        def service_pack_major(self) -> int: ...
+        @property
+        def suite_mast(self) -> int: ...
+        @property
+        def product_type(self) -> int: ...
+        @property
+        def platform_version(self) -> tuple[int, int, int]: ...
    def getwindowsversion() -> _WinVersion: ...


Note to self: I will have to spin up a windows virtual machine to check these. Will mark resolved when done.

Typo: suite_mast --> suite_mask

I have fixed the typo (it predated this PR, FWIW)

Co-authored-by: Akuli <akuviljanen17@gmail.com>

As discussed in python#6816, for some `structseq` classes these attributes are writeable `ClassVar`s, but for other classes, they're read-only `ClassVar`s. Either way, however, it's probably a bad idea to be modifying these attributes, so it makes sense to simply annotate them with `Final` rather than `ClassVar`. Note that [PEP 591](https://www.python.org/dev/peps/pep-0591/) specifically states: > Type checkers should infer a final attribute that is initialized in a class body as being a class variable. Variables should not be annotated with both ClassVar and Final. As such, annotating these attributes as `Final[ClassVar[int]]` would be neither necessary nor possible.

Akuli

Thanks!

github-actions · 2022-01-05T12:48:33Z

According to mypy_primer, this change has no effect on the checked open source code. 🤖🎉

Improve sys stubs

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