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• [*] I have searched (google, github) for similar issues and couldn't find anything
• [*] I have read and followed the docs and still think this is a bug

Bug

             pydantic version: 1.7.1
            pydantic compiled: True
                 install path: /home/user/work/bugs/python/pydantic-ordering/.venv/lib/python3.8/site-packages/pydantic
               python version: 3.8.5 (default, Jul 28 2020, 12:59:40)  [GCC 9.3.0]
                     platform: Linux-4.19.128-microsoft-standard-x86_64-with-glibc2.29
     optional deps. installed: []

Including validate_assignment = True in a model's config seems to cause assignment to change the field order when using dict(). This change was discovered when upgrading to 1.7.0 and also applies to 1.7.1, but was not present in prior versions.

This behaviour does not seem to agree with https://pydantic-docs.helpmanual.io/usage/models/#field-ordering, and is something that is important for my uses (where it generates massive diffs in the output) and surely others.

Running this snippet with and without the validate_assignment line produces different output:

from pydantic import BaseModel

class Model(BaseModel):
    title: str = ''
    name: str = ''

    class Config:
        validate_assignment = True
        ...

m = Model(name='name')
m.title = 'title'
print(m.dict())