add legacy load utility

CHANGELOG.md

@@ -148,6 +148,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Added `RichModelSummary` callback ([#9546](https://github.com/PyTorchLightning/pytorch-lightning/pull/9546))
 
 
+- Added `pl_legacy_patch` load utility for loading old checkpoints that have pickled legacy Lightning attributes ([#9166](https://github.com/PyTorchLightning/pytorch-lightning/pull/9166))
+
+
 ### Changed
 
 - `pytorch_lightning.loggers.neptune.NeptuneLogger` is now consistent with new [neptune-client](https://github.com/neptune-ai/neptune-client) API ([#6867](https://github.com/PyTorchLightning/pytorch-lightning/pull/6867)).
@@ -242,9 +245,6 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Deprecated `on_{train/val/test/predict}_dataloader()` from `LightningModule` and `LightningDataModule` [#9098](https://github.com/PyTorchLightning/pytorch-lightning/pull/9098)
 
 
-- Updated deprecation of  `argparse_utils.py` from removal in 1.4 to 2.0 ([#9162](https://github.com/PyTorchLightning/pytorch-lightning/pull/9162))
-
-
 - Deprecated `on_keyboard_interrupt` callback hook in favor of new `on_exception` hook ([#9260](https://github.com/PyTorchLightning/pytorch-lightning/pull/9260))
 
 
@@ -323,6 +323,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Removed deprecated `profiled_functions` argument from `PyTorchProfiler` ([#9178](https://github.com/PyTorchLightning/pytorch-lightning/pull/9178))
 
 
+- Removed deprecated `pytorch_lighting.utilities.argparse_utils` module ([#9166](https://github.com/PyTorchLightning/pytorch-lightning/pull/9166))
+
+
 - Removed deprecated property `Trainer.running_sanity_check` in favor of `Trainer.sanity_checking` ([#9209](https://github.com/PyTorchLightning/pytorch-lightning/pull/9209))
 
 

pytorch_lightning/core/saving.py

@@ -29,6 +29,7 @@
 from pytorch_lightning.utilities.apply_func import apply_to_collection
 from pytorch_lightning.utilities.cloud_io import get_filesystem
 from pytorch_lightning.utilities.cloud_io import load as pl_load
+from pytorch_lightning.utilities.migration import pl_legacy_patch
 from pytorch_lightning.utilities.parsing import parse_class_init_keys
 
 log = logging.getLogger(__name__)
@@ -125,10 +126,11 @@ def load_from_checkpoint(
             pretrained_model.freeze()
             y_hat = pretrained_model(x)
         """
-        if map_location is not None:
-            checkpoint = pl_load(checkpoint_path, map_location=map_location)
-        else:
-            checkpoint = pl_load(checkpoint_path, map_location=lambda storage, loc: storage)
+        with pl_legacy_patch():
+            if map_location is not None:
+                checkpoint = pl_load(checkpoint_path, map_location=map_location)
+            else:
+                checkpoint = pl_load(checkpoint_path, map_location=lambda storage, loc: storage)
 
         if hparams_file is not None:
             extension = hparams_file.split(".")[-1]

pytorch_lightning/trainer/connectors/checkpoint_connector.py

@@ -26,6 +26,7 @@
 from pytorch_lightning.utilities.cloud_io import atomic_save, get_filesystem
 from pytorch_lightning.utilities.exceptions import MisconfigurationException
 from pytorch_lightning.utilities.imports import _fault_tolerant_training
+from pytorch_lightning.utilities.migration import pl_legacy_patch
 from pytorch_lightning.utilities.types import _PATH
 from pytorch_lightning.utilities.upgrade_checkpoint import KEYS_MAPPING as DEPRECATED_CHECKPOINT_KEYS
 
@@ -65,7 +66,8 @@ def resume_start(self) -> None:
         self._loaded_checkpoint = self._load_and_validate_checkpoint(checkpoint_path)
 
     def _load_and_validate_checkpoint(self, checkpoint_path: _PATH) -> Dict[str, Any]:
-        loaded_checkpoint = self.trainer.training_type_plugin.load_checkpoint(checkpoint_path)
+        with pl_legacy_patch():
+            loaded_checkpoint = self.trainer.training_type_plugin.load_checkpoint(checkpoint_path)
         if any(key in loaded_checkpoint for key in DEPRECATED_CHECKPOINT_KEYS):
             raise ValueError(
                 "The checkpoint you're attempting to load follows an"

pytorch_lightning/utilities/argparse.py

@@ -295,13 +295,6 @@ def _gpus_allowed_type(x: str) -> Union[int, str]:
     return int(x)
 
 
-def _gpus_arg_default(x: str) -> Union[int, str]:  # pragma: no-cover
-    # unused, but here for backward compatibility with old checkpoints that need to be able to
-    # unpickle the function from the checkpoint, as it was not filtered out in versions < 1.2.8
-    # see: https://github.com/PyTorchLightning/pytorch-lightning/pull/6898
-    pass
-
-
 def _int_or_float_type(x: Union[int, float, str]) -> Union[int, float]:
     if "." in str(x):
         return float(x)

pytorch_lightning/utilities/migration.py

@@ -0,0 +1,48 @@
+# Copyright The PyTorch Lightning team.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+import sys
+from types import ModuleType
+
+import pytorch_lightning.utilities.argparse
+
+
+class pl_legacy_patch:
+    """Registers legacy artifacts (classes, methods, etc.) that were removed but still need to be included for
+    unpickling old checkpoints. The following patches apply.
+
+        1. ``pytorch_lightning.utilities.argparse._gpus_arg_default``: Applies to all checkpoints saved prior to
+           version 1.2.8. See: https://github.com/PyTorchLightning/pytorch-lightning/pull/6898
+        2. ``pytorch_lightning.utilities.argparse_utils``: A module that was deprecated in 1.2 and removed in 1.4,
+           but still needs to be available for import for legacy checkpoints.
+
+    Example:
+
+        with pl_legacy_patch():
+            torch.load("path/to/legacy/checkpoint.ckpt")
+    """
+
+    def __enter__(self):
+        # `pl.utilities.argparse_utils` was renamed to `pl.utilities.argparse`
+        legacy_argparse_module = ModuleType("pytorch_lightning.utilities.argparse_utils")
+        sys.modules["pytorch_lightning.utilities.argparse_utils"] = legacy_argparse_module
+
+        # `_gpus_arg_default` used to be imported from these locations
+        legacy_argparse_module._gpus_arg_default = lambda x: x
+        pytorch_lightning.utilities.argparse._gpus_arg_default = lambda x: x
+        return self
+
+    def __exit__(self, exc_type, exc_value, exc_traceback):
+        if hasattr(pytorch_lightning.utilities.argparse, "_gpus_arg_default"):
+            delattr(pytorch_lightning.utilities.argparse, "_gpus_arg_default")
+        del sys.modules["pytorch_lightning.utilities.argparse_utils"]

pytorch_lightning/utilities/upgrade_checkpoint.py

@@ -18,6 +18,7 @@
 import torch
 
 from pytorch_lightning.callbacks import EarlyStopping, ModelCheckpoint
+from pytorch_lightning.utilities.migration import pl_legacy_patch
 
 KEYS_MAPPING = {
     "checkpoint_callback_best_model_score": (ModelCheckpoint, "best_model_score"),
@@ -58,4 +59,5 @@ def upgrade_checkpoint(filepath):
 
     log.info("Creating a backup of the existing checkpoint file before overwriting in the upgrade process.")
     copyfile(args.file, args.file + ".bak")
-    upgrade_checkpoint(args.file)
+    with pl_legacy_patch():
+        upgrade_checkpoint(args.file)

tests/utilities/test_migration.py

@@ -0,0 +1,36 @@
+# Copyright The PyTorch Lightning team.
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+import sys
+
+import pytorch_lightning
+from pytorch_lightning.utilities.migration import pl_legacy_patch
+
+
+def test_patch_legacy_argparse_utils():
+    with pl_legacy_patch():
+        from pytorch_lightning.utilities import argparse_utils
+
+        assert callable(argparse_utils._gpus_arg_default)
+        assert "pytorch_lightning.utilities.argparse_utils" in sys.modules
+
+    assert "pytorch_lightning.utilities.argparse_utils" not in sys.modules
+
+
+def test_patch_legacy_gpus_arg_default():
+    with pl_legacy_patch():
+        from pytorch_lightning.utilities.argparse import _gpus_arg_default
+
+        assert callable(_gpus_arg_default)
+    assert not hasattr(pytorch_lightning.utilities.argparse, "_gpus_arg_default")
+    assert not hasattr(pytorch_lightning.utilities.argparse, "_gpus_arg_default")