Sync enum members logic in typeanal and checkmember

[sterliakov]

Fixes #19686.
Fixes #15540.
Fixes #14600.

[sterliakov]

All new errors in primer stem from invalid enum definitions in stubs - bare annotations are not considered enum members, even in stubs (both by spec and by common sense). To hide a value, stubs should assign ellipsis to enum members. Here's the relevant spec chapter: https://typing.python.org/en/latest/spec/enums.html#defining-members

Do we have direct contact with pandas team? Should I open a ticket to let them know and get that fixed?

https://github.com/pandas-dev/pandas/blob/3940df8255ed04db0089e66ce09a4c986b97cac4/pandas/_libs/tslibs/dtypes.pyi#L30-L43

https://github.com/srittau/python-htmlgen/blob/01e3b911ac282d067850bb324b913e3594bc0e23/htmlgen/video.pyi#L6-L9

[brianschubert]

cc @Dr-Irv for pandas typing

[Dr-Irv]

cc @Dr-Irv for pandas typing

Thanks for the ping. Here is what is happening here. We have some enums defined in cython, which is where the values get set. So in our PYI files, we do things like this:

class FreqGroup(Enum):
    FR_ANN: int
    FR_QTR: int
    FR_MTH: int
    FR_WK: int
    FR_BUS: int
    FR_DAY: int

Then we have code that has things like FreqGroup.FR_MTH.value which is what causes the errors reported above.

Now, for the ones we define in cython, we can change this to the actual values in the PYI files. Not ideal - then we have to maintain the numerical values in two places.

But we also have some that are dependent on values stored in the C code in numpy. Getting those might be a bit difficult.

What's the best way to handle this?

[brianschubert]

You can use ... as a placeholder to omit the runtime values, e.g.

class FreqGroup(Enum):
    FR_ANN = ...

https://typing.python.org/en/latest/spec/enums.html#:~:text=Within%20a%20type%20stub,can%20be%20used

To include type information, you can use cast(int, ...)

[Dr-Irv]

To include type information, you can use cast(int, ...)

I think the following will work:

class FreqGroup(Enum):
    _value_ : int
    FR_ANN = ...

and then we won't need to use cast

[sterliakov]

Yeah, we added _value_ support recently (#19352), _value_ and ellipsis initializer should work now.

[github-actions]

Diff from mypy_primer, showing the effect of this PR on open source code:

python-htmlgen (https://github.com/srittau/python-htmlgen)
+ test_htmlgen/video.py:38: error: Incompatible types in assignment (expression has type "str", variable has type "Preload | None")  [assignment]
+ test_htmlgen/form.py:51: error: Incompatible types in assignment (expression has type "str", variable has type "Autocomplete | None")  [assignment]

[hauntsaninja]

Nice, thank you!