remove generated dataset folders after download tests (#3376)

* remove generated dataset folders after download tests

* revert unnecessary style changes

test/test_datasets_download.py

@@ -3,10 +3,12 @@ import itertools
 import time
 import unittest.mock
 from datetime import datetime
+from distutils import dir_util
 from os import path
 from urllib.error import HTTPError, URLError
 from urllib.parse import urlparse
 from urllib.request import urlopen, Request
+import tempfile
 import warnings
 
 import pytest
@@ -194,6 +196,17 @@ def collect_download_configs(dataset_loader, name=None, **kwargs):
     return make_download_configs(urls_and_md5s, name)
 
 
+# This is a workaround since fixtures, such as the built-in tmp_dir, can only be used within a test but not within a
+# parametrization. Thus, we use a single root directory for all datasets and remove it when all download tests are run.
+ROOT = tempfile.mkdtemp()
+
+
+@pytest.fixture(scope="module", autouse=True)
+def root():
+    yield ROOT
+    dir_util.remove_tree(ROOT)
+
+
 def places365():
     with log_download_attempts(patch=False) as urls_and_md5s:
         for split, small in itertools.product(("train-standard", "train-challenge", "val"), (False, True)):
@@ -206,26 +219,26 @@ def places365():
 
 
 def caltech101():
-    return collect_download_configs(lambda: datasets.Caltech101(".", download=True), name="Caltech101")
+    return collect_download_configs(lambda: datasets.Caltech101(ROOT, download=True), name="Caltech101")
 
 
 def caltech256():
-    return collect_download_configs(lambda: datasets.Caltech256(".", download=True), name="Caltech256")
+    return collect_download_configs(lambda: datasets.Caltech256(ROOT, download=True), name="Caltech256")
 
 
 def cifar10():
-    return collect_download_configs(lambda: datasets.CIFAR10(".", download=True), name="CIFAR10")
+    return collect_download_configs(lambda: datasets.CIFAR10(ROOT, download=True), name="CIFAR10")
 
 
 def cifar100():
-    return collect_download_configs(lambda: datasets.CIFAR100(".", download=True), name="CIFAR100")
+    return collect_download_configs(lambda: datasets.CIFAR100(ROOT, download=True), name="CIFAR100")
 
 
 def voc():
     return itertools.chain(
         *[
             collect_download_configs(
-                lambda: datasets.VOCSegmentation(".", year=year, download=True),
+                lambda: datasets.VOCSegmentation(ROOT, year=year, download=True),
                 name=f"VOC, {year}",
                 file="voc",
             )
@@ -235,27 +248,27 @@ def voc():
 
 
 def mnist():
-    return collect_download_configs(lambda: datasets.MNIST(".", download=True), name="MNIST")
+    return collect_download_configs(lambda: datasets.MNIST(ROOT, download=True), name="MNIST")
 
 
 def fashion_mnist():
-    return collect_download_configs(lambda: datasets.FashionMNIST(".", download=True), name="FashionMNIST")
+    return collect_download_configs(lambda: datasets.FashionMNIST(ROOT, download=True), name="FashionMNIST")
 
 
 def kmnist():
-    return collect_download_configs(lambda: datasets.KMNIST(".", download=True), name="KMNIST")
+    return collect_download_configs(lambda: datasets.KMNIST(ROOT, download=True), name="KMNIST")
 
 
 def emnist():
     # the 'split' argument can be any valid one, since everything is downloaded anyway
-    return collect_download_configs(lambda: datasets.EMNIST(".", split="byclass", download=True), name="EMNIST")
+    return collect_download_configs(lambda: datasets.EMNIST(ROOT, split="byclass", download=True), name="EMNIST")
 
 
 def qmnist():
     return itertools.chain(
         *[
             collect_download_configs(
-                lambda: datasets.QMNIST(".", what=what, download=True),
+                lambda: datasets.QMNIST(ROOT, what=what, download=True),
                 name=f"QMNIST, {what}",
                 file="mnist",
             )
@@ -268,7 +281,7 @@ def omniglot():
     return itertools.chain(
         *[
             collect_download_configs(
-                lambda: datasets.Omniglot(".", background=background, download=True),
+                lambda: datasets.Omniglot(ROOT, background=background, download=True),
                 name=f"Omniglot, {'background' if background else 'evaluation'}",
             )
             for background in (True, False)
@@ -280,7 +293,7 @@ def phototour():
     return itertools.chain(
         *[
             collect_download_configs(
-                lambda: datasets.PhotoTour(".", name=name, download=True),
+                lambda: datasets.PhotoTour(ROOT, name=name, download=True),
                 name=f"PhotoTour, {name}",
                 file="phototour",
             )
@@ -293,7 +306,7 @@ def phototour():
 
 def sbdataset():
     return collect_download_configs(
-        lambda: datasets.SBDataset(".", download=True),
+        lambda: datasets.SBDataset(ROOT, download=True),
         name="SBDataset",
         file="voc",
     )
@@ -301,7 +314,7 @@ def sbdataset():
 
 def sbu():
     return collect_download_configs(
-        lambda: datasets.SBU(".", download=True),
+        lambda: datasets.SBU(ROOT, download=True),
         name="SBU",
         file="sbu",
     )
@@ -309,7 +322,7 @@ def sbu():
 
 def semeion():
     return collect_download_configs(
-        lambda: datasets.SEMEION(".", download=True),
+        lambda: datasets.SEMEION(ROOT, download=True),
         name="SEMEION",
         file="semeion",
     )
@@ -317,7 +330,7 @@ def semeion():
 
 def stl10():
     return collect_download_configs(
-        lambda: datasets.STL10(".", download=True),
+        lambda: datasets.STL10(ROOT, download=True),
         name="STL10",
     )
 
@@ -326,7 +339,7 @@ def svhn():
     return itertools.chain(
         *[
             collect_download_configs(
-                lambda: datasets.SVHN(".", split=split, download=True),
+                lambda: datasets.SVHN(ROOT, split=split, download=True),
                 name=f"SVHN, {split}",
                 file="svhn",
             )
@@ -339,7 +352,7 @@ def usps():
     return itertools.chain(
         *[
             collect_download_configs(
-                lambda: datasets.USPS(".", train=train, download=True),
+                lambda: datasets.USPS(ROOT, train=train, download=True),
                 name=f"USPS, {'train' if train else 'test'}",
                 file="usps",
             )
@@ -350,7 +363,7 @@ def usps():
 
 def celeba():
     return collect_download_configs(
-        lambda: datasets.CelebA(".", download=True),
+        lambda: datasets.CelebA(ROOT, download=True),
         name="CelebA",
         file="celeba",
     )
@@ -358,7 +371,7 @@ def celeba():
 
 def widerface():
     return collect_download_configs(
-        lambda: datasets.WIDERFace(".", download=True),
+        lambda: datasets.WIDERFace(ROOT, download=True),
         name="WIDERFace",
         file="widerface",
     )