TYP: cache_readonly

[twoertwein]

• closes TYP: IntervalIndex.right/left might be infered as function #41588
• tests added / passed
• Ensure all linting tests pass, see here for how to run them
• whatsnew entry

I'm not sure how to test this on the CI - pyright is happy on my machine:

import pandas as pd

index: pd.IntervalIndex = pd.IntervalIndex.from_arrays([1], [2])
reveal_type(index)
reveal_type(index.right)

info: Type of "index" is "IntervalIndex"
info: Type of "index.right" is "Index"

[twoertwein]

I don't know what the variable typ is.

The return value of __get__ can also be self (is that intended?):

pandas/pandas/_libs/properties.pyx

Line 23 in b9e90dc

return self

[jbrockmendel]

The return value of get can also be self (is that intended?):

Yes, this happens when you lookup cls.foo on the class rather than on an instance

[twoertwein]

Thanks, I added an overload for this.

The current type stubs do not handle this case

pandas/pandas/_libs/properties.pyx

Line 30 in b9e90dc

except (AttributeError):

If the only solution to cover this case is to return _G | cache_readonly[_F, _G], I am inclined to not cover this case as it would make the annotations less useful (even though it would be correct): index.right would then be a union of two types.

[jbrockmendel]

If the CI failures prove hard to resolve, could we cheat and write in the .pyi something like class cache_readonly(property): pass?

[twoertwein]

If the CI failures prove hard to resolve, could we cheat and write in the .pyi something like class cache_readonly(property): pass?

I must admit, I didn't notice the many mypy failures. I will put the PR into draft mode and locally debug it until I get it working. I will ping you when it is ready :)

[twoertwein]

If the CI failures prove hard to resolve, could we cheat and write in the .pyi something like class cache_readonly(property): pass?

I mistakenly used Protocol instead of Generic: roughly half of the errors are gone now. There are still many legitimate errors left.

Some remaining [arg-type] errors on unions and [override] errors are probably due to a mypy issue (opened python/mypy#11037).

[twoertwein]

see #41588 (comment)