Dataclass field ordering should not be enforced when init=False

Dataclasses support fields that have default values. All fields with defaults must appear after all fields without default values. Mypy enforces this ordering requirement and emits an error ("Attributes without a default cannot follow attributes with one") if it is violated. Pyright does the same.

By default, dataclasses include a synthesized __init__ method, but this behavior can be overridden by including an init=False argument to the dataclass decorator.

A pyright user recently submitted a bug report indicating that the field order requirement should not be enforced when init=False. I've re-read PEP 557, and it doesn't provide clarity on this point.

Either mypy and pyright are both doing the right thing here or both of them have a bug.

Perhaps someone who was involved in the development of PEP 557, the dataclass implementation, or the mypy dataclass internal plugin could help clarify which behavior is correct?

Inizia esaminando PEP 557, l’implementazione di dataclass e il plugin interno dataclass di mypy, quindi confronta il comportamento segnalato in pyright issue 1753. Determina se l’errore relativo all’ordine dei campi debba applicarsi quando il decoratore dataclass usa init=False, quindi documenta o implementa il comportamento concordato.