Fixed EH and error reporting in restore_from (#3583)

* Fixed EH and error reporting in restore_from

Signed-off-by: Boris Fomitchev <bfomitchev@nvidia.com>

* --amend

Signed-off-by: Boris Fomitchev <bfomitchev@nvidia.com>

* Fixed merge issue

Signed-off-by: Boris Fomitchev <bfomitchev@nvidia.com>

Co-authored-by: Eric Harper <complex451@gmail.com>

nemo/core/classes/common.py

@@ -442,45 +442,31 @@ def from_config_dict(cls, config: 'DictConfig', trainer: Optional['Trainer'] = N
             instance = hydra.utils.instantiate(config=config)
         else:
             instance = None
-            imported_cls_tb = None
-            instance_init_error = None
+            prev_error = ""
             # Attempt class path resolution from config `target` class (if it exists)
             if 'target' in config:
                 target_cls = config["target"]  # No guarantee that this is a omegaconf class
                 imported_cls = None
                 try:
                     # try to import the target class
                     imported_cls = import_class_by_path(target_cls)
-                except Exception:
-                    imported_cls_tb = traceback.format_exc()
-
-                # try instantiating model with target class
-                if imported_cls is not None:
                     # if calling class (cls) is subclass of imported class,
                     # use subclass instead
                     if issubclass(cls, imported_cls):
                         imported_cls = cls
-
-                    try:
-                        accepts_trainer = Serialization._inspect_signature_for_trainer(imported_cls)
-                        if accepts_trainer:
-                            instance = imported_cls(cfg=config, trainer=trainer)
-                        else:
-                            instance = imported_cls(cfg=config)
-
-                    except Exception as e:
-                        imported_cls_tb = traceback.format_exc()
-                        instance_init_error = str(e)
-                        instance = None
+                    accepts_trainer = Serialization._inspect_signature_for_trainer(imported_cls)
+                    if accepts_trainer:
+                        instance = imported_cls(cfg=config, trainer=trainer)
+                    else:
+                        instance = imported_cls(cfg=config)
+                except Exception as e:
+                    # record previous error
+                    tb = traceback.format_exc()
+                    prev_error = f"Model instantiation failed!\nTarget class:\t{target_cls}" f"\nError(s):\t{e}\n{tb}"
+                    logging.debug(prev_error + "\nFalling back to `cls`.")
 
             # target class resolution was unsuccessful, fall back to current `cls`
             if instance is None:
-                if imported_cls_tb is not None:
-                    logging.info(
-                        f"Model instantiation from target class {target_cls} failed with following error.\n"
-                        f"Falling back to `cls`.\n"
-                        f"{imported_cls_tb}"
-                    )
                 try:
                     accepts_trainer = Serialization._inspect_signature_for_trainer(cls)
                     if accepts_trainer:
@@ -489,9 +475,9 @@ def from_config_dict(cls, config: 'DictConfig', trainer: Optional['Trainer'] = N
                         instance = cls(cfg=config)
 
                 except Exception as e:
-                    if imported_cls_tb is not None:
-                        logging.error(f"Instance failed restore_from due to: {instance_init_error}")
-                        logging.error(f"{imported_cls_tb}")
+                    # report saved errors, if any, and raise
+                    if prev_error:
+                        logging.error(prev_error)
                     raise e
 
         if not hasattr(instance, '_cfg'):