copy_on_model_validation config doesn't copy List field anymore in v1.9.0

[NunchakusLei]

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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

The output of python -c "import pydantic.utils; print(pydantic.utils.version_info())" when I use v1.9.0a1,

             pydantic version: 1.9.0a1
            pydantic compiled: True
                 install path: <*my-project-dir*>/venv/lib/python3.9/site-packages/pydantic
               python version: 3.9.9 (main, Nov 16 2021, 03:05:18)  [GCC 7.5.0]
                     platform: Linux-5.4.0-91-generic-x86_64-with-glibc2.27
     optional deps. installed: ['typing-extensions']

The output of python -c "import pydantic.utils; print(pydantic.utils.version_info())" when I use v1.9.0,

             pydantic version: 1.9.0
            pydantic compiled: True
                 install path: <*my-project-dir*>/venv/lib/python3.9/site-packages/pydantic
               python version: 3.9.9 (main, Nov 16 2021, 03:05:18)  [GCC 7.5.0]
                     platform: Linux-5.4.0-91-generic-x86_64-with-glibc2.27
     optional deps. installed: ['typing-extensions']

Looks like there is accidental behaviour change from v1.9.0a1 to v1.9.0 regarding the copy_on_model_validation config.

from pydantic import BaseModel
from typing import List


class A(BaseModel):
    name: str
    
    class Config:
        copy_on_model_validation = True  # Default behaviour
        

class B(BaseModel):
    list_a: List[A]


a = A(name="a")
b = B(list_a=[a])

print(a)
print(b)
a.name = "b"  # make a change to variable a's field
print(a)
print(b)

The output using v1.9.0a1,

A(name='a')
B(list_a=[A(name='a')])
A(name='b')
B(list_a=[A(name='a')])

The output using v1.9.0 changed to,

A(name='a')
B(list_a=[A(name='a')])
A(name='b')
B(list_a=[A(name='b')])

[NunchakusLei]

This issue happens again in the latest version 1.9.2.

[timkpaine]

#4093 (comment)