breaking change with 3.14: local method `list()` interferes with typing

[parmentelat]

with this input file here

https://github.com/fit-r2lab/rhubarbe/blob/292f58ae86db47e7443bc49e51a1011be2178f61/rhubarbe/inventorypdus.py

I am seeing this error with a newly installed Python-3.14
It was working just fine with 3.13

In [3]: InventoryPdus.from_yaml("""
   ...: pdu_hosts: []
   ...: devices: []
   ...: """)

---------------------------------------------------------------------------
KeyError                                  Traceback (most recent call last)
File ~/miniconda3/envs/rhubarbe/lib/python3.14/site-packages/dataclass_wizard/loader_selection.py:75, in fromdict(cls, d)
     74 try:
---> 75     load = CLASS_TO_LOAD_FUNC[cls]
     76 except KeyError:

KeyError: <class 'rhubarbe.inventorypdus.InventoryPdus'>

During handling of the above exception, another exception occurred:

TypeError                                 Traceback (most recent call last)
Cell In[3], line 1
----> 1 InventoryPdus.from_yaml("""
      2 pdu_hosts: []
      3 devices: []
      4 """)

File ~/miniconda3/envs/rhubarbe/lib/python3.14/site-packages/dataclass_wizard/wizard_mixins.py:254, in YAMLWizard.from_yaml(cls, string_or_stream, decoder, **decoder_kwargs)
    250     decoder = yaml.safe_load
    252 o = decoder(string_or_stream, **decoder_kwargs)
--> 254 return fromdict(cls, o) if isinstance(o, dict) else fromlist(cls, o)

<snip>

File ~/miniconda3/envs/rhubarbe/lib/python3.14/annotationlib.py:205, in ForwardRef.evaluate(self, globals, locals, type_params, owner, format)
    203 code = self.__forward_code__
    204 try:
--> 205     return eval(code, globals=globals, locals=locals)
    206 except Exception:
    207     if not is_forwardref_format:

File <string>:1

TypeError: 'function' object is not subscriptable

I'm eager to hear if this rings a bell

I can also turn this into a Minimal Reproducible Example, if it helps pinpointing the issue, just let me know

[parmentelat]

FWIW, I eventually figured it out

turns out my wizarded class had a local list method
the problem disappeared once I rename this method into something else

see also this commit on how I fixed it
fit-r2lab/rhubarbe@458a088

I have no clear idea on how this is even possible

not sure if that needs further action, but I'm going to leave this issue open in case someone has a clue

[parmentelat]

here's a MRE:

# file crash.py
from dataclasses import dataclass
from dataclass_wizard import YAMLWizard

@dataclass
class KO(YAMLWizard):
    items: list[str]

    def list(self):
        pass

@dataclass
class OK(YAMLWizard):
    items: list[str]

then run the following sentence in both 3.13 and 3.14

python -c 'from crash import *; print(KO.from_yaml("[]"))'

and you will observe the crash in 3.14 only

[rnag]

Hi @parmentelat — thanks for the minimal repro! I can reproduce this on Python 3.14.

From the traceback, the failure happens while evaluating a forward reference / annotation expression:

TypeError: 'function' object is not subscriptable
...
annotationlib.py -> eval(code, globals=..., locals=...)

This is consistent with a name collision during annotation evaluation: in your module List resolves to the user-defined function List(...) instead of typing.List, so List[int] ends up trying to subscript a function.

I agree this is worth treating as a bug on our side — we should make annotation resolution more robust in the presence of user-defined names that shadow typing/builtins. I’ll track this and work on a fix (likely by tightening the globals/locals used for forward-ref evaluation and/or using a safer annotation resolver path on 3.14).

Thanks again for the repro — it was very helpful.

[parmentelat]

hiya
just wanted to draw your attention on my using builtin list and not typing.List
not that it matters much but for the sake of accuracy :-)
I could work around that by renaming my method, so end of crisis on my end, but indeed I believe this needs ironing out

[rnag]

@parmentelat Yep, good point — I meant the builtin list type.

It turns out the same behavior also affects other common annotations such as
typing.List, typing.Dict, and even builtins like dict when a method
with the same name exists on the class.

Here’s a minimal repro:

# crash.py
from typing import List
from dataclasses import dataclass
from dataclass_wizard import YAMLWizard

@dataclass
class KO(YAMLWizard):
    items: List[str]

    def List(self):
        pass

@dataclass
class OK(YAMLWizard):
    items: List[str]

print(KO.from_yaml("[]"))

This appears to be a behavior change in Python 3.14+, so we’ll likely need to
special-case or guard against it on our side. For now, I’m fine keeping this
issue open to track the fix.