Loading from last checkpoint functionality in Trainer.train (#10334)

Enhance resume_from_checkpoint argument of Trainer.train to accept
bool type. If True given, last saved checkpoint in self.args.output_dir
will be loaded. (#10280)

src/transformers/trainer.py

@@ -97,6 +97,7 @@ from .trainer_utils import (
     TrainOutput,
     default_compute_objective,
     default_hp_space,
+    get_last_checkpoint,
     set_seed,
     speed_metrics,
 )
@@ -758,7 +759,7 @@ class Trainer:
 
     def train(
         self,
-        resume_from_checkpoint: Optional[str] = None,
+        resume_from_checkpoint: Optional[Union[str, bool]] = None,
         trial: Union["optuna.Trial", Dict[str, Any]] = None,
         **kwargs,
     ):
@@ -766,9 +767,11 @@ class Trainer:
         Main training entry point.
 
         Args:
-            resume_from_checkpoint (:obj:`str`, `optional`):
-                Local path to a saved checkpoint as saved by a previous instance of :class:`~transformers.Trainer`. If
-                present, training will resume from the model/optimizer/scheduler states loaded here.
+            resume_from_checkpoint (:obj:`str` or :obj:`bool`, `optional`):
+                If a :obj:`str`, local path to a saved checkpoint as saved by a previous instance of
+                :class:`~transformers.Trainer`. If a :obj:`bool` and equals `True`, load the last checkpoint in
+                `args.output_dir` as saved by a previous instance of :class:`~transformers.Trainer`. If present,
+                training will resume from the model/optimizer/scheduler states loaded here.
             trial (:obj:`optuna.Trial` or :obj:`Dict[str, Any]`, `optional`):
                 The trial run or the hyperparameter dictionary for hyperparameter search.
             kwargs:
@@ -803,6 +806,11 @@ class Trainer:
             self.optimizer, self.lr_scheduler = None, None
 
         # Load potential model checkpoint
+        if isinstance(resume_from_checkpoint, bool) and resume_from_checkpoint:
+            resume_from_checkpoint = get_last_checkpoint(self.args.output_dir)
+            if resume_from_checkpoint is None:
+                raise ValueError(f"No valid checkpoint found in output directory ({self.args.output_dir})")
+
         if resume_from_checkpoint is not None and os.path.isfile(os.path.join(resume_from_checkpoint, WEIGHTS_NAME)):
             logger.info(f"Loading model from {resume_from_checkpoint}).")
             if isinstance(self.model, PreTrainedModel):