Fix frozen dataclass instance error in apply_to_collection

CHANGELOG.md

@@ -34,6 +34,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Show a better error message when a custom `DataLoader` implementation is not well implemented and we need to reconstruct it ([#10719](https://github.com/PyTorchLightning/pytorch-lightning/issues/10719))
 
 
+- Show a better error message when frozen dataclass is used as a batch ([#10927](https://github.com/PyTorchLightning/pytorch-lightning/issues/10927))
+
+
 - Save the `Loop`'s state by default in the checkpoint ([#10784](https://github.com/PyTorchLightning/pytorch-lightning/issues/10784))
 
 

pytorch_lightning/utilities/apply_func.py

@@ -23,6 +23,7 @@
 import numpy as np
 import torch
 
+from pytorch_lightning.utilities.exceptions import MisconfigurationException
 from pytorch_lightning.utilities.imports import _compare_version, _TORCHTEXT_LEGACY
 from pytorch_lightning.utilities.warnings import rank_zero_deprecation
 
@@ -147,7 +148,13 @@ def apply_to_collection(
                 )
             if not field_init or (not include_none and v is None):  # retain old value
                 v = getattr(data, field_name)
-            setattr(result, field_name, v)
+            try:
+                setattr(result, field_name, v)
+            except dataclasses.FrozenInstanceError as e:
+                raise MisconfigurationException(
+                    "A frozen dataclass was passed to `apply_to_collection` but this is not allowed."
+                    " HINT: is your batch a frozen dataclass?"
+                ) from e
         return result
 
     # data is neither of dtype, nor a collection

tests/utilities/test_apply_func.py

@@ -22,6 +22,7 @@
 import torch
 
 from pytorch_lightning.utilities.apply_func import apply_to_collection, apply_to_collections, move_data_to_device
+from pytorch_lightning.utilities.exceptions import MisconfigurationException
 
 
 def test_recursive_application_to_collection():
@@ -302,6 +303,17 @@ def fn(a, b):
     assert reduced is None
 
 
+def test_apply_to_collection_frozen_dataclass():
+    @dataclasses.dataclass(frozen=True)
+    class Foo:
+        input: torch.Tensor
+
+    foo = Foo(torch.tensor(0))
+
+    with pytest.raises(MisconfigurationException, match="frozen dataclass was passed"):
+        apply_to_collection(foo, torch.Tensor, lambda t: t.to(torch.int))
+
+
 @pytest.mark.parametrize("should_return", [False, True])
 def test_wrongly_implemented_transferable_data_type(should_return):
     class TensorObject: