Document dataclass field should not be reused

Documentation

The current implementation of dataclass modifies a field in place. Thereby, the following code will modify f:

from dataclasses import dataclass, field

f = field(kw_only=True)

@dataclass
class A:
    x: int = f
    y: int = f

print(f) # now f.name is filled
# furthermore, A is broken (or does not behave if we used two different field instance)

It can create issues when we have multiple fields that have the same spec and we reuse the same Field instance to set the same metadata to all of them. A class is created but it's garbage.

IMHO, in the docs, we should warn the user to NOT share any Field instance.

Linked PRs

• gh-145373
• gh-145387

Inizia esaminando la documentazione di dataclass e Field e le PR collegati gh-145373 e gh-145387. Aggiungi un avviso chiaro a non riutilizzare un’istanza di Field tra i campi di dataclass e considera completo l’esempio nell’issue quando le indicazioni documentate affrontano la mutazione risultante e il comportamento errato della classe.