LiteDataLoader wrapper improvements

pytorch_lightning/lite/wrappers.py

@@ -15,7 +15,7 @@
 import inspect
 from contextlib import contextmanager
 from itertools import chain
-from typing import Any, Callable, Dict, Generator, Iterator, Optional, Set, Type, Union
+from typing import Any, Callable, Generator, Iterator, Optional, Set, Type, Union
 
 import torch
 from torch import nn as nn
@@ -110,21 +110,25 @@ def _convert_float_tensor(t: Tensor) -> Tensor:
         return output
 
 
-def _wrap_init(f: Callable) -> Callable:
-    @functools.wraps(f)
-    def wrapper(module: Any, *args: Any, **kwargs: Dict[str, Any]) -> None:
-        params = dict(inspect.signature(module._old_init).parameters)
+def _wrap_init(init: Callable) -> Callable:
+    """Wraps the ``__init__`` method of the dataloader in order to enable re-instantiation of custom subclasses of
+    :class:`~torch.utils.data.DataLoader`."""
+
+    @functools.wraps(init)
+    def wrapper(obj: DataLoader, *args: Any, **kwargs: Any) -> None:
+        params = dict(inspect.signature(obj.__init__).parameters)
         params.pop("args", None)
         params.pop("kwargs", None)
-        for init_name, init_arg in chain(zip(params, args), kwargs.items()):
-            setattr(module, init_name, init_arg)
-        f(module, *args, **kwargs)
+        for arg_name, arg_value in chain(zip(params, args), kwargs.items()):
+            setattr(obj, arg_name, arg_value)
+        init(obj, *args, **kwargs)
 
     return wrapper
 
 
 # https://stackoverflow.com/a/63851681/9201239
 def _get_all_subclasses(cls: Type[Any]) -> Set[Type[Any]]:
+    """Returns a list of all classes that inherit directly or indirectly from the given class."""
     subclasses = set()
 
     def recurse(cl: Type[Any]) -> None:
@@ -136,24 +140,17 @@ def recurse(cl: Type[Any]) -> None:
     return subclasses
 
 
-def _enable_class(cls: Type[Any]) -> None:
-    cls._old_init = cls.__init__
-    cls.__init__ = _wrap_init(cls.__init__)
-
-
-def _disable_class(cls: Type[Any]) -> None:
-    cls.__init__ = cls._old_init
-    del cls._old_init
-
-
 @contextmanager
-def _replace_dataloader_init_method() -> Generator:
-    """This context manager is used to support custom :class:`~torch.utils.data.DataLoader."""
+def _replace_dataloader_init_method() -> Generator[None, None, None]:
+    """This context manager is used to add support for re-instantiation of custom (subclasses) of
+    :class:`~torch.utils.data.DataLoader`. It patches the ``__init__`` method."""
     for subclass in _get_all_subclasses(DataLoader):
-        _enable_class(subclass)
+        subclass._old_init = subclass.__init__
+        subclass.__init__ = _wrap_init(subclass.__init__)
     yield
     for subclass in _get_all_subclasses(DataLoader):
-        _disable_class(subclass)
+        subclass.__init__ = subclass._old_init
+        del subclass._old_init
 
 
 class _LiteDataLoader:

tests/lite/test_lite.py

@@ -24,12 +24,7 @@
 from torch.utils.data import DataLoader, DistributedSampler, Sampler
 
 from pytorch_lightning.lite import LightningLite
-from pytorch_lightning.lite.wrappers import (
-    _LiteDataLoader,
-    _LiteModule,
-    _LiteOptimizer,
-    _replace_dataloader_init_method,
-)
+from pytorch_lightning.lite.wrappers import _LiteDataLoader, _LiteModule, _LiteOptimizer
 from pytorch_lightning.plugins import DeepSpeedPlugin, PrecisionPlugin, TrainingTypePlugin
 from pytorch_lightning.utilities import _StrategyType
 from pytorch_lightning.utilities.exceptions import MisconfigurationException
@@ -197,6 +192,27 @@ def run(self):
     LiteWithCustomDataLoader().run()
 
 
+def test_setup_dataloaders_raises_for_unknown_custom_args():
+    """Test that an error raises when custom dataloaders with unknown arguments are created from outside Lite's run
+    method."""
+    lite = EmptyLite()
+
+    class CustomDataLoader(DataLoader):
+        def __init__(self, new_arg, *args, **kwargs):
+            super().__init__(range(5), *args, **kwargs)
+
+    with pytest.raises(
+        MisconfigurationException,
+        match=(
+            r"Trying to inject `DistributedSampler` into the `CustomDataLoader` instance.*"
+            r"The missing attributes are \['new_arg'\]"
+        ),
+    ):
+        # The dataloader was not created within the run function, and therefore init args were not intercepted
+        dataloader = CustomDataLoader(2, batch_size=2)
+        lite.setup_dataloaders(dataloader)
+
+
 def test_setup_dataloaders_twice_fails():
     """Test that calling setup_dataloaders with a dataloader that is already wrapped fails."""
     lite = EmptyLite()
@@ -444,25 +460,3 @@ def run(self):
             assert self.is_global_zero == (self.local_rank == 0)
 
     Lite(strategy=DeepSpeedPlugin(stage=3, logging_batch_size_per_gpu=1), devices=2, accelerator="gpu").run()
-
-
-def test_replace_dataloader_init_method():
-    """Test that the context manager enables to save the parameters passed to the DataLoader __init__ method."""
-
-    class CustomDataLoader(DataLoader):
-        def __init__(self, extra_argument: int, *args, **kwargs):
-            super().__init__(*args, **kwargs)
-
-    dataloader = CustomDataLoader(extra_argument=1, dataset=range(1))
-    lite = EmptyLite()
-    with pytest.raises(MisconfigurationException, match="extra_argument"):
-        dataloader = lite.setup_dataloaders(dataloader)
-
-    with _replace_dataloader_init_method():
-        dataloader = CustomDataLoader(extra_argument=1, dataset=range(1))
-        assert dataloader.extra_argument == 1
-        dataloader = lite.setup_dataloaders(dataloader)
-
-        dataloader = CustomDataLoader(1, range(1))
-        assert dataloader.extra_argument == 1
-        dataloader = lite.setup_dataloaders(dataloader)