Fix datamodules ImportError and add tests (#380)

* Warn when unavailable

* Add tests

* Add more to the tests

* Fix experience_source

* Fix vocdetection_datamodule

* Fix imagenet

* Update test_imports

* Fix kitti

* Apply suggestions from code review

Co-authored-by: Jirka Borovec <Borda@users.noreply.github.com>

* Add docstring to tests

Co-authored-by: Jirka Borovec <Borda@users.noreply.github.com>

pl_bolts/datamodules/experience_source.py

@@ -2,14 +2,23 @@
 Datamodules for RL models that rely on experiences generated during training
 Based on implementations found here: https://github.com/Shmuma/ptan/blob/master/ptan/experience.py
 """
+import importlib
 from abc import ABC
 from collections import deque, namedtuple
 from typing import Callable, Iterable, List, Tuple
 
 import torch
-from gym import Env
 from torch.utils.data import IterableDataset
 
+from pl_bolts.utils.warnings import warn_missing_pkg
+
+_GYM_AVAILABLE = importlib.util.find_spec("gym") is not None
+if _GYM_AVAILABLE:
+    from gym import Env
+else:
+    warn_missing_pkg("gym")  # pragma: no-cover
+
+
 # Datasets
 
 Experience = namedtuple(
@@ -172,7 +181,7 @@ def env_actions(self, device) -> List[List[int]]:
 
         return actions
 
-    def env_step(self, env_idx: int, env: Env, action: List[int]) -> Experience:
+    def env_step(self, env_idx: int, env: "Env", action: List[int]) -> Experience:
         """
         Carries out a step through the given environment using the given action
 
@@ -236,7 +245,7 @@ def pop_rewards_steps(self):
 class DiscountedExperienceSource(ExperienceSource):
     """Outputs experiences with a discounted reward over N steps"""
 
-    def __init__(self, env: Env, agent, n_steps: int = 1, gamma: float = 0.99):
+    def __init__(self, env: "Env", agent, n_steps: int = 1, gamma: float = 0.99):
         super().__init__(env, agent, (n_steps + 1))
         self.gamma = gamma
         self.steps = n_steps

pl_bolts/datamodules/kitti_datamodule.py

@@ -1,12 +1,19 @@
+import importlib
 import os
 
 import torch
-import torchvision.transforms as transforms
 from pytorch_lightning import LightningDataModule
 from torch.utils.data import DataLoader
 from torch.utils.data.dataset import random_split
 
 from pl_bolts.datasets.kitti_dataset import KittiDataset
+from pl_bolts.utils.warnings import warn_missing_pkg
+
+_TORCHVISION_AVAILABLE = importlib.util.find_spec("torchvision") is not None
+if _TORCHVISION_AVAILABLE:
+    import torchvision.transforms as transforms
+else:
+    warn_missing_pkg('torchvision')  # pragma: no-cover
 
 
 class KittiDataModule(LightningDataModule):
@@ -56,6 +63,11 @@ def __init__(
             batch_size: the batch size
             seed: random seed to be used for train/val/test splits
         """
+        if not _TORCHVISION_AVAILABLE:
+            raise ModuleNotFoundError(  # pragma: no-cover
+                'You want to use `torchvision` which is not installed yet.'
+            )
+
         super().__init__(*args, **kwargs)
         self.data_dir = data_dir if data_dir is not None else os.getcwd()
         self.batch_size = batch_size

pl_bolts/datamodules/sklearn_datamodule.py

@@ -6,11 +6,12 @@
 from pytorch_lightning import LightningDataModule
 from torch.utils.data import DataLoader, Dataset
 
+from pl_bolts.utils.warnings import warn_missing_pkg
+
 try:
     from sklearn.utils import shuffle as sk_shuffle
 except ModuleNotFoundError:
-    raise ModuleNotFoundError('You want to use `sklearn` which is not installed yet,'  # pragma: no-cover
-                              ' install it with `pip install sklearn`.')
+    warn_missing_pkg("sklearn")  # pragma: no-cover
     _SKLEARN_AVAILABLE = False
 else:
     _SKLEARN_AVAILABLE = True

pl_bolts/datamodules/vocdetection_datamodule.py

@@ -1,13 +1,12 @@
 import torch
-import torchvision.transforms as T
 from pytorch_lightning import LightningDataModule
 from torch.utils.data import DataLoader
 
 from pl_bolts.utils.warnings import warn_missing_pkg
 
 try:
+    import torchvision.transforms as T
     from torchvision.datasets import VOCDetection
-
 except ModuleNotFoundError:
     warn_missing_pkg('torchvision')  # pragma: no-cover
     _TORCHVISION_AVAILABLE = False

pl_bolts/datasets/imagenet_dataset.py

@@ -11,13 +11,14 @@
 import torch
 from torch._six import PY3
 
+from pl_bolts.utils.warnings import warn_missing_pkg
+
 try:
     from torchvision.datasets import ImageNet
     from torchvision.datasets.imagenet import load_meta_file
-except ModuleNotFoundError as err:
-    raise ModuleNotFoundError(  # pragma: no-cover
-        'You want to use `torchvision` which is not installed yet, install it with `pip install torchvision`.'
-    ) from err
+except ModuleNotFoundError:
+    warn_missing_pkg('torchvision')  # pragma: no-cover
+    ImageNet = object
 
 
 class UnlabeledImagenet(ImageNet):

pl_bolts/datasets/kitti_dataset.py

@@ -1,9 +1,18 @@
+import importlib
 import os
 
 import numpy as np
-from PIL import Image
 from torch.utils.data import Dataset
 
+from pl_bolts.utils.warnings import warn_missing_pkg
+
+_PIL_AVAILABLE = importlib.util.find_spec("PIL") is not None
+if _PIL_AVAILABLE:
+    from PIL import Image
+else:
+    warn_missing_pkg('PIL')  # pragma: no-cover
+
+
 DEFAULT_VOID_LABELS = (0, 1, 2, 3, 4, 5, 6, 9, 10, 14, 15, 16, 18, 29, 30, -1)
 DEFAULT_VALID_LABELS = (7, 8, 11, 12, 13, 17, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 31, 32, 33)
 
@@ -41,6 +50,11 @@ def __init__(
             void_labels: useless classes to be excluded from training
             valid_labels: useful classes to include
         """
+        if not _PIL_AVAILABLE:
+            raise ModuleNotFoundError(  # pragma: no-cover
+                'You want to use `PIL` which is not installed yet.'
+            )
+
         self.img_size = img_size
         self.void_labels = void_labels
         self.valid_labels = valid_labels

tests/datamodules/test_imports.py

@@ -0,0 +1,37 @@
+import importlib
+from unittest import mock
+
+import pytest
+
+
+@pytest.mark.parametrize("dm_cls,deps", [
+    ("AsynchronousLoader", []),
+    ("BinaryMNISTDataModule", ["torchvision"]),
+    ("CIFAR10DataModule", ["torchvision"]),
+    ("TinyCIFAR10DataModule", ["torchvision"]),
+    ("DiscountedExperienceSource", ["gym"]),
+    ("ExperienceSource", ["gym"]),
+    ("ExperienceSourceDataset", ["gym"]),
+    ("FashionMNISTDataModule", ["torchvision"]),
+    ("ImagenetDataModule", ["torchvision"]),
+    ("MNISTDataModule", ["torchvision"]),
+    ("SklearnDataModule", ["sklearn"]),
+    ("SklearnDataset", []),
+    ("TensorDataset", []),
+    ("SSLImagenetDataModule", ["torchvision"]),
+    ("STL10DataModule", ["torchvision"]),
+    ("VOCDetectionDataModule", ["torchvision"]),
+    ("CityscapesDataModule", ["torchvision"]),
+    ("KittiDataset", ["PIL"]),
+    ("KittiDataModule", ["torchvision"]),
+])
+def test_import(dm_cls, deps):
+    """Tests importing when dependencies are not met.
+
+    Set the followings in @pytest.mark.parametrize:
+        dm_cls: class to test importing
+        deps: packages required for dm_cls
+    """
+    with mock.patch.dict("sys.modules", {pkg: None for pkg in deps}):
+        dms_module = importlib.import_module("pl_bolts.datamodules")
+        assert hasattr(dms_module, dm_cls), f"`from pl_bolts.datamodules import {dm_cls}` failed."