Fix saving hyperparameters in a composition where parent is not a LM or LDM

src/pytorch_lightning/CHANGELOG.md

@@ -70,6 +70,10 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Fixed epoch-end logging results not being reset after the end of the epoch ([#14061](https://github.com/Lightning-AI/lightning/pull/14061))
 
 
+- Fix saving hyperparameters in a composition where the parent class is not a `LightningModule` or `LightningDataModule` ([#14151](https://github.com/Lightning-AI/lightning/pull/14151))
+
+
+
 ## [1.7.1] - 2022-08-09
 
 ### Fixed

src/pytorch_lightning/utilities/parsing.py

@@ -162,14 +162,18 @@ def get_init_args(frame: types.FrameType) -> Dict[str, Any]:
 
 
 def collect_init_args(
-    frame: types.FrameType, path_args: List[Dict[str, Any]], inside: bool = False
+    frame: types.FrameType,
+    path_args: List[Dict[str, Any]],
+    inside: bool = False,
+    classes: Tuple[Type, ...] = (object,),
 ) -> List[Dict[str, Any]]:
     """Recursively collects the arguments passed to the child constructors in the inheritance tree.
 
     Args:
         frame: the current stack frame
         path_args: a list of dictionaries containing the constructor args in all parent classes
         inside: track if we are inside inheritance path, avoid terminating too soon
+        classes: the classes in which to inspect the frames
 
     Return:
           A list of dictionaries where each dictionary contains the arguments passed to the
@@ -181,13 +185,13 @@ def collect_init_args(
     if not isinstance(frame.f_back, types.FrameType):
         return path_args
 
-    if "__class__" in local_vars:
+    if "__class__" in local_vars and issubclass(local_vars["__class__"], classes):
         local_args = get_init_args(frame)
         # recursive update
         path_args.append(local_args)
-        return collect_init_args(frame.f_back, path_args, inside=True)
+        return collect_init_args(frame.f_back, path_args, inside=True, classes=classes)
     if not inside:
-        return collect_init_args(frame.f_back, path_args, inside)
+        return collect_init_args(frame.f_back, path_args, inside, classes=classes)
     return path_args
 
 
@@ -225,7 +229,10 @@ def save_hyperparameters(
         init_args = {f.name: getattr(obj, f.name) for f in fields(obj)}
     else:
         init_args = {}
-        for local_args in collect_init_args(frame, []):
+
+        from pytorch_lightning.core.mixins import HyperparametersMixin
+
+        for local_args in collect_init_args(frame, [], classes=(HyperparametersMixin,)):
             init_args.update(local_args)
 
     if ignore is None:

tests/tests_pytorch/models/test_hparams.py

@@ -29,6 +29,7 @@
 from pytorch_lightning import LightningModule, Trainer
 from pytorch_lightning.callbacks import ModelCheckpoint
 from pytorch_lightning.core.datamodule import LightningDataModule
+from pytorch_lightning.core.mixins import HyperparametersMixin
 from pytorch_lightning.core.saving import load_hparams_from_yaml, save_hparams_to_yaml
 from pytorch_lightning.demos.boring_classes import BoringDataModule, BoringModel, RandomDataset
 from pytorch_lightning.utilities import _OMEGACONF_AVAILABLE, AttributeDict, is_picklable
@@ -399,6 +400,24 @@ def _raw_checkpoint_path(trainer) -> str:
     return raw_checkpoint_path
 
 
+@pytest.mark.parametrize("base_class", (HyperparametersMixin, LightningModule, LightningDataModule))
+def test_save_hyperparameters_under_composition(base_class):
+    """Test that in a composition where the parent is not a Lightning-like module, the parent's arguments don't get
+    collected."""
+
+    class ChildInComposition(base_class):
+        def __init__(self, same_arg):
+            super().__init__()
+            self.save_hyperparameters()
+
+    class NotPLSubclass:  # intentionally not subclassing LightningModule/LightningDataModule
+        def __init__(self, same_arg="parent_default", other_arg="other"):
+            self.child = ChildInComposition(same_arg="cocofruit")
+
+    parent = NotPLSubclass()
+    assert parent.child.hparams == dict(same_arg="cocofruit")
+
+
 class LocalVariableModelSuperLast(BoringModel):
     """This model has the super().__init__() call at the end."""