[codemod][py3.12] Convert dataclasses mutable default values to use d…

…efault_factory

Summary:
As of [Python 3.11](https://docs.python.org/3.11/whatsnew/3.11.html#dataclasses), dataclasses now only allow defaults that are hashable. Using mutable (non-hashable) default values under Python 3.11+ will cause a runtime error:

```
ValueError: mutable default <class 'problematic.ClassName'> for field <field> is not allowed: use default_factory
```

This codemod attempts to automatically convert mutable defaults to use `default_factory`

NOTE: The change is not semantically equivalent to before the change. Before, all dataclass instances with a mutable default value were sharing the same instance. This change results each dataclass instance using a new instance of the mutable value. It is likely that the before state was a latent bug, but it's still a behavior change!

Reviewed By: itamaro

Differential Revision: D70448655

fbshipit-source-id: 09b49467f1fe54f5ea9669de401f4f9cceadc06e

mmf/modules/encoders.py

@@ -6,7 +6,7 @@
 import re
 from collections import OrderedDict
 from copy import deepcopy
-from dataclasses import asdict, dataclass
+from dataclasses import asdict, dataclass, field
 from enum import Enum
 from typing import Any
 
@@ -591,11 +591,15 @@ class MultiModalEncoderBase(Encoder):
     @dataclass
     class Config(Encoder.Config):
         # This actually is Union[ImageEncoderConfig, ImageFeatureEncoderConfig]
-        modal_encoder: EncoderFactory.Config = ImageEncoderFactory.Config(
-            type=ImageEncoderTypes.resnet152, params=ResNet152ImageEncoder.Config()
+        modal_encoder: EncoderFactory.Config = field(
+            default_factory=lambda: ImageEncoderFactory.Config(
+                type=ImageEncoderTypes.resnet152, params=ResNet152ImageEncoder.Config()
+            )
         )
-        text_encoder: EncoderFactory.Config = TextEncoderFactory.Config(
-            type=TextEncoderTypes.transformer, params=TransformerEncoder.Config()
+        text_encoder: EncoderFactory.Config = field(
+            default_factory=lambda: TextEncoderFactory.Config(
+                type=TextEncoderTypes.transformer, params=TransformerEncoder.Config()
+            )
         )
         direct_features_input: bool = False
         modal_hidden_size: int = 2048