Deprecate `LightningDataModule.on_save/load_checkpoint` (#11893)

CHANGELOG.md

@@ -482,6 +482,9 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Deprecated `PrecisionPlugin.on_{save,load}_checkpoint` in favor of `PrecisionPlugin.{state_dict,load_state_dict}` ([#11978](https://github.com/PyTorchLightning/pytorch-lightning/pull/11978))
 
 
+- Deprecated `LightningDataModule.on_save/load_checkpoint` in favor of `state_dict/load_state_dict` ([#11893](https://github.com/PyTorchLightning/pytorch-lightning/pull/11893))
+
+
 ### Removed
 
 - Removed deprecated parameter `method` in `pytorch_lightning.utilities.model_helpers.is_overridden` ([#10507](https://github.com/PyTorchLightning/pytorch-lightning/pull/10507))

docs/source/extensions/datamodules.rst

@@ -323,16 +323,16 @@ on_after_batch_transfer
 .. automethod:: pytorch_lightning.core.datamodule.LightningDataModule.on_after_batch_transfer
     :noindex:
 
-on_load_checkpoint
+load_state_dict
 ~~~~~~~~~~~~~~~~~~
 
-.. automethod:: pytorch_lightning.core.datamodule.LightningDataModule.on_load_checkpoint
+.. automethod:: pytorch_lightning.core.datamodule.LightningDataModule.load_state_dict
     :noindex:
 
-on_save_checkpoint
+state_dict
 ~~~~~~~~~~~~~~~~~~
 
-.. automethod:: pytorch_lightning.core.datamodule.LightningDataModule.on_save_checkpoint
+.. automethod:: pytorch_lightning.core.datamodule.LightningDataModule.state_dict
     :noindex:
 
 on_train_dataloader

pytorch_lightning/trainer/configuration_validator.py

@@ -62,6 +62,8 @@ def verify_loop_configurations(trainer: "pl.Trainer") -> None:
     _check_precision_plugin_checkpoint_hooks(trainer)
     # TODO: Delete on_pretrain_routine_start/end hooks in v1.8
     _check_on_pretrain_routine(model)
+    # TODO: Delete CheckpointHooks off LightningDataModule in v1.8
+    _check_datamodule_checkpoint_hooks(trainer)
 
 
 def __verify_train_val_loop_configuration(trainer: "pl.Trainer", model: "pl.LightningModule") -> None:
@@ -395,3 +397,16 @@ def _check_precision_plugin_checkpoint_hooks(trainer: "pl.Trainer") -> None:
             "`PrecisionPlugin.on_load_checkpoint` was deprecated in"
             " v1.6 and will be removed in v1.8. Use `load_state_dict` instead."
         )
+
+
+def _check_datamodule_checkpoint_hooks(trainer: "pl.Trainer") -> None:
+    if is_overridden(method_name="on_save_checkpoint", instance=trainer.datamodule):
+        rank_zero_deprecation(
+            "`LightningDataModule.on_save_checkpoint` was deprecated in"
+            " v1.6 and will be removed in v1.8. Use `state_dict` instead."
+        )
+    if is_overridden(method_name="on_load_checkpoint", instance=trainer.datamodule):
+        rank_zero_deprecation(
+            "`LightningDataModule.on_load_checkpoint` was deprecated in"
+            " v1.6 and will be removed in v1.8. Use `load_state_dict` instead."
+        )

tests/core/test_datamodules.py

@@ -222,6 +222,10 @@ def test_dm_checkpoint_save_and_load(tmpdir):
     )
 
     # fit model
+    with pytest.deprecated_call(
+        match="`LightningDataModule.on_save_checkpoint` was deprecated in"
+        " v1.6 and will be removed in v1.8. Use `state_dict` instead."
+    ):
         trainer.fit(model, datamodule=dm)
     assert trainer.state.finished, f"Training failed with {trainer.state}"
     checkpoint_path = list(trainer.checkpoint_callback.best_k_models.keys())[0]

tests/deprecated_api/test_remove_1-8.py

@@ -36,6 +36,7 @@ from pytorch_lightning.plugins.training_type.single_device import SingleDevicePl
 from pytorch_lightning.plugins.training_type.single_tpu import SingleTPUPlugin
 from pytorch_lightning.plugins.training_type.tpu_spawn import TPUSpawnPlugin
 from pytorch_lightning.profiler import AbstractProfiler, AdvancedProfiler, SimpleProfiler
+from pytorch_lightning.trainer.configuration_validator import _check_datamodule_checkpoint_hooks
 from pytorch_lightning.trainer.states import RunningStage
 from pytorch_lightning.utilities.apply_func import move_data_to_device
 from pytorch_lightning.utilities.enums import DeviceType, DistributedType
@@ -740,3 +741,29 @@ def test_v1_8_0_precision_plugin_checkpoint_hooks(tmpdir):
 
 def test_v1_8_0_abstract_profiler():
     assert "`AbstractProfiler` was deprecated in v1.6" in AbstractProfiler.__doc__
+
+
+def test_v1_8_0_datamodule_checkpointhooks():
+    class CustomBoringDataModuleSave(BoringDataModule):
+        def on_save_checkpoint(self, checkpoint):
+            print("override on_save_checkpoint")
+
+    class CustomBoringDataModuleLoad(BoringDataModule):
+        def on_load_checkpoint(self, checkpoint):
+            print("override on_load_checkpoint")
+
+    trainer = Mock()
+
+    trainer.datamodule = CustomBoringDataModuleSave()
+    with pytest.deprecated_call(
+        match="`LightningDataModule.on_save_checkpoint` was deprecated in"
+        " v1.6 and will be removed in v1.8. Use `state_dict` instead."
+    ):
+        _check_datamodule_checkpoint_hooks(trainer)
+
+    trainer.datamodule = CustomBoringDataModuleLoad()
+    with pytest.deprecated_call(
+        match="`LightningDataModule.on_load_checkpoint` was deprecated in"
+        " v1.6 and will be removed in v1.8. Use `load_state_dict` instead."
+    ):
+        _check_datamodule_checkpoint_hooks(trainer)