Fix from_argparse_args (#380)

* Fix from_argparse_args

* Update CHANGELOG.md

CHANGELOG.md

@@ -27,6 +27,7 @@ The format is based on [Keep a Changelog](http://keepachangelog.com/en/1.0.0/).
 - Fixed `flash.Trainer.add_argparse_args` not adding any arguments ([#343](https://github.com/PyTorchLightning/lightning-flash/pull/343))
 - Fixed a bug where using `val_split` with `overfit_batches` would give an infinite recursion ([#375](https://github.com/PyTorchLightning/lightning-flash/pull/375))
 - Fixed a bug where some timm models were mistakenly given a `global_pool` argument ([#376](https://github.com/PyTorchLightning/lightning-flash/pull/376))
+- Fixed `flash.Trainer.from_argparse_args` not passing arguments correctly ([#380](https://github.com/PyTorchLightning/lightning-flash/pull/380))
 
 
 ## [0.3.0] - 2021-05-20

flash/core/trainer.py

@@ -11,8 +11,9 @@
 # WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 # See the License for the specific language governing permissions and
 # limitations under the License.
+import inspect
 import warnings
-from argparse import ArgumentParser
+from argparse import ArgumentParser, Namespace
 from functools import wraps
 from typing import Callable, List, Optional, Union
 
@@ -29,6 +30,22 @@
 from flash.core.finetuning import _DEFAULTS_FINETUNE_STRATEGIES, instantiate_default_finetuning_callbacks
 
 
+def from_argparse_args(cls, args: Union[Namespace, ArgumentParser], **kwargs):
+    """Modified version of ``pytorch_lightning.utilities.argparse.from_argparse_args`` which populates ``valid_kwargs``
+    from ``pytorch_lightning.Trainer``."""
+    if isinstance(args, ArgumentParser):
+        args = cls.parse_argparser(args)
+
+    params = vars(args)
+
+    # we only want to pass in valid PLTrainer args, the rest may be user specific
+    valid_kwargs = inspect.signature(PlTrainer.__init__).parameters
+    trainer_kwargs = dict((name, params[name]) for name in valid_kwargs if name in params)
+    trainer_kwargs.update(**kwargs)
+
+    return cls(**trainer_kwargs)
+
+
 def _defaults_from_env_vars(fn: Callable) -> Callable:
     """Copy of ``pytorch_lightning.trainer.connectors.env_vars_connector._defaults_from_env_vars``. Required to fix
     build error in readthedocs."""
@@ -180,3 +197,9 @@ def add_argparse_args(cls, *args, **kwargs) -> ArgumentParser:
         # the lightning trainer implementation does not support subclasses.
         # context: https://github.com/PyTorchLightning/lightning-flash/issues/342#issuecomment-848892447
         return add_argparse_args(PlTrainer, *args, **kwargs)
+
+    @classmethod
+    def from_argparse_args(cls, args: Union[Namespace, ArgumentParser], **kwargs) -> 'Trainer':
+        # the lightning trainer implementation does not support subclasses.
+        # context: https://github.com/PyTorchLightning/lightning-flash/issues/342#issuecomment-848892447
+        return from_argparse_args(PlTrainer, args, **kwargs)

tests/core/test_trainer.py

@@ -118,3 +118,11 @@ def test_add_argparse_args():
     parser = Trainer.add_argparse_args(parser)
     args = parser.parse_args(['--gpus=1'])
     assert args.gpus == 1
+
+
+def test_from_argparse_args():
+    parser = ArgumentParser()
+    parser = Trainer.add_argparse_args(parser)
+    args = parser.parse_args(['--max_epochs=200'])
+    trainer = Trainer.from_argparse_args(args)
+    assert trainer.max_epochs == 200