Performance regression with repeated fields in Python 3.10

[BenRKarl]

Environment details

• Programming language: Python
• OS: gLinux
• Language runtime version: 3.9.5 and 3.10.0
• Package version: 1.19.0

Steps to reproduce

1. Run the below script using Python 3.9.5
2. Run it again using Python 3.10.0 and compare the results

import proto
from timeit import timeit

class Attribute(proto.Message):
    name = proto.Field(
        proto.STRING,
        number=1
    )

class Cat(proto.Message):
    attributes = proto.RepeatedField(
        Attribute,
        number=1,
    )

cat = Cat()
print(timeit(lambda: list(cat.attributes), number=1000))

For more context see the original issue on the Ads library.

[BenRKarl]

FYI I think this issue is likely a problem with protobuf defaulting to the python implementation when installed. See 9014 for context. I'm going to close this for now, will reopen if there's any indication of an issue in proto-plus