fix HttpResource.resolve() with preprocessing (#5669)

* fix HttpResource.resolve() with preprocess set

* fix README

* add safe guard for invalid str inputs

test/test_prototype_datasets_utils.py

@@ -5,6 +5,7 @@ import pytest
 import torch
 from datasets_utils import make_fake_flo_file
 from torchvision.datasets._optical_flow import _read_flo as read_flo_ref
+from torchvision.prototype.datasets.utils import HttpResource, GDriveResource
 from torchvision.prototype.datasets.utils._internal import read_flo, fromfile
 
 
@@ -45,3 +46,58 @@ def test_read_flo(tmpdir):
     expected = torch.from_numpy(read_flo_ref(path).astype("f4", copy=False))
 
     torch.testing.assert_close(actual, expected)
+
+
+class TestHttpResource:
+    def test_resolve_to_http(self, mocker):
+        file_name = "data.tar"
+        original_url = f"http://downloads.pytorch.org/{file_name}"
+
+        redirected_url = original_url.replace("http", "https")
+
+        sha256_sentinel = "sha256_sentinel"
+
+        def preprocess_sentinel(path):
+            return path
+
+        original_resource = HttpResource(
+            original_url,
+            sha256=sha256_sentinel,
+            preprocess=preprocess_sentinel,
+        )
+
+        mocker.patch("torchvision.prototype.datasets.utils._resource._get_redirect_url", return_value=redirected_url)
+        redirected_resource = original_resource.resolve()
+
+        assert isinstance(redirected_resource, HttpResource)
+        assert redirected_resource.url == redirected_url
+        assert redirected_resource.file_name == file_name
+        assert redirected_resource.sha256 == sha256_sentinel
+        assert redirected_resource._preprocess is preprocess_sentinel
+
+    def test_resolve_to_gdrive(self, mocker):
+        file_name = "data.tar"
+        original_url = f"http://downloads.pytorch.org/{file_name}"
+
+        id_sentinel = "id-sentinel"
+        redirected_url = f"https://drive.google.com/file/d/{id_sentinel}/view"
+
+        sha256_sentinel = "sha256_sentinel"
+
+        def preprocess_sentinel(path):
+            return path
+
+        original_resource = HttpResource(
+            original_url,
+            sha256=sha256_sentinel,
+            preprocess=preprocess_sentinel,
+        )
+
+        mocker.patch("torchvision.prototype.datasets.utils._resource._get_redirect_url", return_value=redirected_url)
+        redirected_resource = original_resource.resolve()
+
+        assert isinstance(redirected_resource, GDriveResource)
+        assert redirected_resource.id == id_sentinel
+        assert redirected_resource.file_name == file_name
+        assert redirected_resource.sha256 == sha256_sentinel
+        assert redirected_resource._preprocess is preprocess_sentinel

torchvision/prototype/datasets/_builtin/README.md

@@ -231,7 +231,7 @@ To generate the `$NAME.categories` file, run `python -m torchvision.prototype.da
 ### What if a resource file forms an I/O bottleneck?
 
 In general, we are ok with small performance hits of iterating archives rather than their extracted content. However, if
-the performance hit becomes significant, the archives can still be decompressed or extracted. To do this, the
-`decompress: bool` and `extract: bool` flags can be used for every `OnlineResource` individually. For more complex
-cases, each resource also accepts a `preprocess` callable that gets passed a `pathlib.Path` of the raw file and should
-return `pathlib.Path` of the preprocessed file or folder.
+the performance hit becomes significant, the archives can still be preprocessed. `OnlineResource` accepts the
+`preprocess` parameter that can be a `Callable[[pathlib.Path], pathlib.Path]` where the input points to the file to be
+preprocessed and the return value should be the result of the preprocessing to load. For convenience, `preprocess` also
+accepts `"decompress"` and `"extract"` to handle these common scenarios.

torchvision/prototype/datasets/_builtin/caltech.py

@@ -32,7 +32,7 @@ class Caltech101(Dataset):
         images = HttpResource(
             "http://www.vision.caltech.edu/Image_Datasets/Caltech101/101_ObjectCategories.tar.gz",
             sha256="af6ece2f339791ca20f855943d8b55dd60892c0a25105fcd631ee3d6430f9926",
-            decompress=True,
+            preprocess="decompress",
         )
         anns = HttpResource(
             "http://www.vision.caltech.edu/Image_Datasets/Caltech101/Annotations.tar",

torchvision/prototype/datasets/_builtin/cub200.py

@@ -51,29 +51,29 @@ class CUB200(Dataset):
             archive = HttpResource(
                 "http://www.vision.caltech.edu/visipedia-data/CUB-200-2011/CUB_200_2011.tgz",
                 sha256="0c685df5597a8b24909f6a7c9db6d11e008733779a671760afef78feb49bf081",
-                decompress=True,
+                preprocess="decompress",
             )
             segmentations = HttpResource(
                 "http://www.vision.caltech.edu/visipedia-data/CUB-200-2011/segmentations.tgz",
                 sha256="dc77f6cffea0cbe2e41d4201115c8f29a6320ecb04fffd2444f51b8066e4b84f",
-                decompress=True,
+                preprocess="decompress",
             )
             return [archive, segmentations]
         else:  # config.year == "2010"
             split = HttpResource(
                 "http://www.vision.caltech.edu/visipedia-data/CUB-200/lists.tgz",
                 sha256="aeacbd5e3539ae84ea726e8a266a9a119c18f055cd80f3836d5eb4500b005428",
-                decompress=True,
+                preprocess="decompress",
             )
             images = HttpResource(
                 "http://www.vision.caltech.edu/visipedia-data/CUB-200/images.tgz",
                 sha256="2a6d2246bbb9778ca03aa94e2e683ccb4f8821a36b7f235c0822e659d60a803e",
-                decompress=True,
+                preprocess="decompress",
             )
             anns = HttpResource(
                 "http://www.vision.caltech.edu/visipedia-data/CUB-200/annotations.tgz",
                 sha256="c17b7841c21a66aa44ba8fe92369cc95dfc998946081828b1d7b8a4b716805c1",
-                decompress=True,
+                preprocess="decompress",
             )
             return [split, images, anns]
 

torchvision/prototype/datasets/_builtin/dtd.py

@@ -49,7 +49,7 @@ class DTD(Dataset):
         archive = HttpResource(
             "https://www.robots.ox.ac.uk/~vgg/data/dtd/download/dtd-r1.0.1.tar.gz",
             sha256="e42855a52a4950a3b59612834602aa253914755c95b0cff9ead6d07395f8e205",
-            decompress=True,
+            preprocess="decompress",
         )
         return [archive]
 

torchvision/prototype/datasets/_builtin/oxford_iiit_pet.py

@@ -40,12 +40,12 @@ class OxfordIITPet(Dataset):
         images = HttpResource(
             "https://www.robots.ox.ac.uk/~vgg/data/pets/data/images.tar.gz",
             sha256="67195c5e1c01f1ab5f9b6a5d22b8c27a580d896ece458917e61d459337fa318d",
-            decompress=True,
+            preprocess="decompress",
         )
         anns = HttpResource(
             "https://www.robots.ox.ac.uk/~vgg/data/pets/data/annotations.tar.gz",
             sha256="52425fb6de5c424942b7626b428656fcbd798db970a937df61750c0f1d358e91",
-            decompress=True,
+            preprocess="decompress",
         )
         return [images, anns]
 

torchvision/prototype/datasets/_builtin/pcam.py

@@ -91,7 +91,7 @@ class PCAM(Dataset):
 
     def resources(self, config: DatasetConfig) -> List[OnlineResource]:
         return [  # = [images resource, targets resource]
-            GDriveResource(file_name=file_name, id=gdrive_id, sha256=sha256, decompress=True)
+            GDriveResource(file_name=file_name, id=gdrive_id, sha256=sha256, preprocess="decompress")
             for file_name, gdrive_id, sha256 in self._RESOURCES[config.split]
         ]
 

torchvision/prototype/datasets/utils/_resource.py

@@ -23,6 +23,7 @@ from torchvision.datasets.utils import (
     _get_redirect_url,
     _get_google_drive_file_id,
 )
+from typing_extensions import Literal
 
 
 class OnlineResource(abc.ABC):
@@ -31,19 +32,22 @@ class OnlineResource(abc.ABC):
         *,
         file_name: str,
         sha256: Optional[str] = None,
-        decompress: bool = False,
-        extract: bool = False,
+        preprocess: Optional[Union[Literal["decompress", "extract"], Callable[[pathlib.Path], pathlib.Path]]] = None,
     ) -> None:
         self.file_name = file_name
         self.sha256 = sha256
 
-        self._preprocess: Optional[Callable[[pathlib.Path], pathlib.Path]]
-        if extract:
-            self._preprocess = self._extract
-        elif decompress:
-            self._preprocess = self._decompress
+        if isinstance(preprocess, str):
+            if preprocess == "decompress":
+                preprocess = self._decompress
+            elif preprocess == "extract":
+                preprocess = self._extract
             else:
-            self._preprocess = None
+                raise ValueError(
+                    f"Only `'decompress'` or `'extract'` are valid if `preprocess` is passed as string,"
+                    f"but got {preprocess} instead."
+                )
+        self._preprocess = preprocess
 
     @staticmethod
     def _extract(file: pathlib.Path) -> pathlib.Path:
@@ -163,7 +167,6 @@ class HttpResource(OnlineResource):
                 "file_name",
                 "sha256",
                 "_preprocess",
-                "_loader",
             )
         }