collections-named-tuple (PYI024): Documented fix is not equivalent

[Avasam]

Summary

From the doc:

Example

from collections import namedtuple

person = namedtuple("Person", ["name", "age"])

Use instead:

from typing import NamedTuple

class Person(NamedTuple):
    name: str
    age: int

But that's not equivalent! Since the variable name person differs from the class name Person.

For this to be equivalent:

from collections import namedtuple

person = namedtuple("Person", ["name", "age"])
Rect = namedtuple("Rect", ["x", "y"])

This would be used:

from typing import NamedTuple

class person(NamedTuple):
    __name__ = "Person"
    name: str
    age: int

class Rect(NamedTuple):
    x: int
    y: int

or

from typing import NamedTuple

class Person(NamedTuple):
    name: str
    age: int
person = Person  # old name

class Rect(NamedTuple):
    x: int
    y: int

I wouldn't recommend that usage. But backwards compatibility is important in libraries, where NamedTuples matter more.

[MichaReiser]

It took me a while to understand what the difference is because I thought it was some subtlety with named tuples when all it is is just the naming of the person variable.

I suggest that we simply change the example in the docs to:

from collections import namedtuple

Person = namedtuple("Person", ["name", "age"])

The rule doesn't have an auto fix and library authors should be aware that changing the casing of an exported variable (if it is exported) is a breaking change.

[Avasam]

(I'm going to bed but doc changes are easy, no need for rust knowledge and I can do it tomorrow if no one completed it already, I just needed a decision)

[MichaReiser]

Thank you and thanks for reporting the issue. We could consider adding a snapshot test for this with a comment. Just in case we ever add a fix for this (as you requested in the other issue). This seems easy to overlook