validate_assignment does not work with root_validator

[caldwellshane]

Output of python -c "import pydantic.utils; print(pydantic.utils.version_info())":

             pydantic version: 1.5.1
            pydantic compiled: True
                 install path: /Users/shane/repos/domain-model-specification/Python/.venv/lib/python3.7/site-packages/pydantic
               python version: 3.7.7 (default, Jul 18 2020, 22:28:30)  [Clang 11.0.3 (clang-1103.0.32.62)]
                     platform: Darwin-19.6.0-x86_64-i386-64bit
     optional deps. installed: ['typing-extensions']

Minimal Example

I'd like to enforce a condition on a whole model during arbitrary changes in its state:

from pydantic import BaseModel, root_validator

class Example(BaseModel):
    current_value: float
    max_value: float

    class Config:
        validate_assignment = True

    @root_validator
    def current_lessequal_max(cls, values):
        current_value = values.get("current_value")
        max_value = values.get("max_value")
        assert abs(current_value) <= max_value, f"current_value cannot be greater than max_value"
        return values

Based on my reading of the docs I'd expect this to fail validation if I set current_value above max_value, or set max_value below current_value, on an existing instance. Is that not the intended behavior?

Thanks for an excellent library!

[PrettyWood]

Hello @caldwellshane

I agree with you the behaviour should be the same as a regular validator.
I opened a PR to fix this issue. We will see if it is accepted ;)