There are a number of issues around recursive types, in general PEP 563
doesn't make a big difference either way in this case.
I think you mean something like
from pydantic import BaseModel
from typing import Optional
class Foo(BaseModel):
x: int
foo: Optional['Foo']
Foo.update_forward_refs()
print(Foo(x=1, foo={'x': 1}))
The only difference with "from __future__ import annotations" is you can
unquote Foo, e.g. Optional[Foo]. In all cases you still need
"Foo.update_forward_refs()" since Foo is not defined while creating Foo.
You could also use ForwardRef: "FooType =
ForwardRef('Foo')...Optional[FooType]", but that's slightly more verbose
and doesn't add anything.
(*Sidenote:* as I'm writing this, I realise you could know what Foo is
while creating Foo (same name -> reference to itself) and perhaps
automatically call update_forward_refs() at the end of
ModelMetaclass.__new__(), but you still need the
public update_forward_refs() for more complex cases; not least bodging
around PEP 563 scopes, see here
<https://github.com/samuelcolvin/pydantic/issues/2678#issuecomment-821437650>
.)
Samuel
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