Enhance pydantic types, add info about actual expected type of a value.

[Bobronium]

Feature Request

As per koxudaxi/pydantic-pycharm-plugin#36, it's hard to PyCharm plugin to reveal actual expected type for the field.

Same goes for #1034 (#1034 (comment))

Why wouldn't we have special attribute, pointing to the actual expected type on all pydantic specific types?

Maybe have a base-generic class and declare types by inheritance from it, like:

class PydanticType(Generic[T]): 
    __expected_type__ = T
    __get_validators__: Callable[..., CallableGenerator]
    ...

# and then:
class StrictBool(bool, PydanticType[bool]:
    ...

[samuelcolvin]

I understand the problem, but what do we do about built in types? Although there aren't that many of them, they're the vast majority of actual usage.

Instead we could have a big dictionary (or function) for lookup up types to show input types are permitted.

Even this wouldn't work for all cases, e.g. '123' is a valid input for type int, but 'xxx' is not.

[dmontagu]

I wouldn't mind if the default behavior was to assume the __expected_type__ was the type itself, and only set anything on other types when that is not the case. I see the point about builtins; given that, I think the dictionary approach @samuelcolvin suggested is probably better.

I believe it should be possible to statically look for such information while building the pydantic __init__ signature (in mypy / pycharm). But it probably wouldn't be very fun to implement.

I wouldn't mind if int allowed str as inputs in __init__ (at least, in non-strict mode), even though it could sometimes fail. It would still be nice though for StrictInt to raise a mypy error if I passed a str for that field.

[Bobronium]

I actually don't get the point about built-in types.
Oh, ok, I got it...

Then dict approach is good for built-ins, however what if someone have his own defined types in a project? It seems there's no way to tell plugin/signature generator that his type actually expects many other types. (Ok, I guess it would be possible to patch dictionary ad runtime, however at type-checking it doesn't seem possible)

I was able to implement it similar way as described in original post:

class StrictBool(int, PydanticType[bool]):
    ...

You can see implementation details here:
master...MrMrRobat:pydantic-types
Maybe I should open PR?

[ycd]

Any updates on this?

[samuelcolvin]

fixed in #5324, some more work to do.