[Core] return_config=True now extracts just config, not full tarfile

nemo/collections/nlp/parts/nlp_overrides.py

@@ -372,7 +372,7 @@ def restore_from(
         loaded_params = super().load_config_and_state_dict(
             calling_cls, restore_path, override_config_path, map_location, strict, return_config, trainer,
         )
-        if not isinstance(loaded_params, tuple):
+        if not isinstance(loaded_params, tuple) or return_config is True:
             return loaded_params
         conf, instance, state_dict = loaded_params
         state_dict = self.modify_state_dict(conf, state_dict)

nemo/core/connectors/save_restore_connector.py

@@ -126,7 +126,9 @@ def load_config_and_state_dict(
 
                 else:
                     # Extract the nemo file into the temporary directory
-                    self._unpack_nemo_file(path2file=restore_path, out_folder=tmpdir)
+                    self._unpack_nemo_file(
+                        path2file=restore_path, out_folder=tmpdir, extract_config_only=return_config is True
+                    )
 
                 # Change current working directory to
                 os.chdir(tmpdir)
@@ -239,7 +241,7 @@ def restore_from(
         loaded_params = self.load_config_and_state_dict(
             calling_cls, restore_path, override_config_path, map_location, strict, return_config, trainer,
         )
-        if not isinstance(loaded_params, tuple):
+        if not isinstance(loaded_params, tuple) or return_config is True:
             return loaded_params
         conf, instance, state_dict = loaded_params
         state_dict = self.modify_state_dict(conf, state_dict)
@@ -532,7 +534,7 @@ def _make_nemo_file_from_folder(filename, source_dir):
             tar.add(source_dir, arcname=".")
 
     @staticmethod
-    def _unpack_nemo_file(path2file: str, out_folder: str) -> str:
+    def _unpack_nemo_file(path2file: str, out_folder: str, extract_config_only: bool = False) -> str:
         if not os.path.exists(path2file):
             raise FileNotFoundError(f"{path2file} does not exist")
 
@@ -546,7 +548,11 @@ def _unpack_nemo_file(path2file: str, out_folder: str) -> str:
             # can be older checkpoint => try compressed tar
             tar_header = "r:gz"
         tar = tarfile.open(path2file, tar_header)
-        tar.extractall(path=out_folder)
+        if not extract_config_only:
+            tar.extractall(path=out_folder)
+        else:
+            members = [x for x in tar.getmembers() if ".yaml" in x.name]
+            tar.extractall(path=out_folder, members=members)
         tar.close()
         return out_folder
 

tests/core/test_save_restore.py

@@ -708,6 +708,69 @@ class MockModelV2(MockModel):
             assert type(restored_model) == MockModelV2
             assert type(restored_model._save_restore_connector) == MySaveRestoreConnector
 
+    @pytest.mark.unit
+    def test_restore_from_save_restore_connector_return_config(self):
+        class MySaveRestoreConnector(save_restore_connector.SaveRestoreConnector):
+            def save_to(self, model, save_path: str):
+                save_path = save_path.replace(".nemo", "_XYZ.nemo")
+                super().save_to(model, save_path)
+
+        class MockModelV2(MockModel):
+            pass
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            # Update config
+            cfg = _mock_model_config()
+
+            # Create model
+            save_path = os.path.join(tmpdir, 'save_custom.nemo')
+            model_with_custom_connector = MockModel(cfg=cfg.model, trainer=None)
+            model_with_custom_connector._save_restore_connector = MySaveRestoreConnector()
+            model_with_custom_connector.save_to(save_path)
+
+            assert os.path.exists(os.path.join(tmpdir, 'save_custom_XYZ.nemo'))
+
+            restored_model_cfg = MockModelV2.restore_from(
+                save_path.replace(".nemo", "_XYZ.nemo"),
+                save_restore_connector=MySaveRestoreConnector(),
+                return_config=True,
+            )
+            assert isinstance(restored_model_cfg, DictConfig)
+            assert model_with_custom_connector.cfg == restored_model_cfg
+
+    @pytest.mark.unit
+    def test_restore_from_save_restore_connector_return_config_partial_tar_extraction(self):
+        class MySaveRestoreConnector(save_restore_connector.SaveRestoreConnector):
+            def save_to(self, model, save_path: str):
+                save_path = save_path.replace(".nemo", "_XYZ.nemo")
+                super().save_to(model, save_path)
+
+        class MockModelV2(MockModel):
+            pass
+
+        with tempfile.TemporaryDirectory() as tmpdir:
+            # Update config
+            cfg = _mock_model_config()
+
+            # Create model
+            save_path = os.path.join(tmpdir, 'save_custom.nemo')
+            model_with_custom_connector = MockModel(cfg=cfg.model, trainer=None)
+            model_with_custom_connector._save_restore_connector = MySaveRestoreConnector()
+            model_with_custom_connector.save_to(save_path)
+
+            true_save_path = os.path.join(tmpdir, 'save_custom_XYZ.nemo')
+            assert os.path.exists(true_save_path)
+
+            my_connector = MySaveRestoreConnector()
+
+            with tempfile.TemporaryDirectory() as config_tmpdir:
+                my_connector._unpack_nemo_file(true_save_path, out_folder=config_tmpdir, extract_config_only=True)
+                current_files = list(os.listdir(config_tmpdir))
+
+                assert len(current_files) == 1  # only config file should have been extracted, no pytorch params
+                config_filepath = current_files[0]
+                assert config_filepath.endswith(".yaml")
+
     @pytest.mark.unit
     def test_mock_model_model_collision(self):
         # The usual pipeline is working just fine.