[BUG] LetterCase.SNAKE renders names with letters and numbers incorrectly.

[davidharcombe]

Description

When rendering a field called cardsV2 or cards_v2 as LetterCase.SNAKE, the output should be

cards_v2

The current version of dataclasses_json (v0.6.7) however renders this as

cards_v_2

Code snippet that reproduces the issue

import dataclasses
import dataclasses_json


@dataclasses_json.dataclass_json(letter_case=dataclasses_json.LetterCase.SNAKE)
@dataclasses.dataclass
class Message(object):
  cardsV2: str

m = Message(cardsV2='card')
print(m.to_dict())

Output:

{'cards_v_2': 'card'}

Describe the results you expected

{'cards_v2': 'card'}

Changing my dataclasses_json in requirements.txt to

dataclasses_json==0.5.7

causes this output to be returned.

Python version you are using

Python 3.11.9

Environment description

asttokens==2.4.1
autopep8==2.0.2
bleach==6.0.0
build==0.10.0
certifi==2023.5.7
cffi==1.15.1
charset-normalizer==3.1.0
comm==0.2.0
cryptography==41.0.1
dataclasses-json>=0.5.7
debugpy==1.8.0
decorator==5.1.1
docutils==0.20.1
executing==2.0.1
idna==3.4
importlib-metadata==6.6.0
ipykernel==6.27.1
ipython==8.18.1
jaraco.classes==3.2.3
jedi==0.19.1
jeepney==0.8.0
jupyter_client==8.6.0
jupyter_core==5.5.0
keyring==23.13.1
markdown-it-py==2.2.0
marshmallow==3.19.0
marshmallow-enum==1.5.1
matplotlib-inline==0.1.6
mdurl==0.1.2
more-itertools==9.1.0
mypy-extensions==1.0.0
nest-asyncio==1.5.8
packaging==23.1
parso==0.8.3
pexpect==4.9.0
pkginfo==1.9.6
platformdirs==4.1.0
prompt-toolkit==3.0.41
psutil==5.9.6
ptyprocess==0.7.0
pure-eval==0.2.2
pycodestyle==2.10.0
pycparser==2.21
Pygments==2.15.1
pyproject_hooks==1.0.0
python-dateutil==2.8.2
pyzmq==25.1.1
readme-renderer==37.3
requests==2.31.0
requests-toolbelt==1.0.0
rfc3986==2.0.0
rich==13.4.1
SecretStorage==3.3.3
six==1.16.0
stack-data==0.6.3
stringcase==1.2.0
tornado==6.4
traitlets==5.14.0
twine==4.0.2
typing-inspect==0.9.0
typing_extensions==4.6.3
urllib3==2.0.3
wcwidth==0.2.12
webencodings==0.5.1
zipp==3.15.0