From eea25cc2e2ef38fe0084348c7577fd121263b4b8 Mon Sep 17 00:00:00 2001
From: Philip Meier <github.pmeier@posteo.de>
Date: Fri, 31 Dec 2021 10:40:02 +0100
Subject: [PATCH 1/3] resolve redirection for HTTP resources

---
 .../prototype/datasets/utils/_resource.py     | 34 +++++++++++++++++++
 1 file changed, 34 insertions(+)

diff --git a/torchvision/prototype/datasets/utils/_resource.py b/torchvision/prototype/datasets/utils/_resource.py
index 94603bfc81e..35a0dd210f8 100644
--- a/torchvision/prototype/datasets/utils/_resource.py
+++ b/torchvision/prototype/datasets/utils/_resource.py
@@ -21,6 +21,8 @@
     extract_archive,
     _decompress,
     download_file_from_google_drive,
+    _get_redirect_url,
+    _get_google_drive_file_id,
 )
 
 
@@ -141,8 +143,40 @@ def __init__(
         super().__init__(file_name=file_name or pathlib.Path(urlparse(url).path).name, **kwargs)
         self.url = url
         self.mirrors = mirrors
+        self._resolved = False
+
+    @property
+    def resolved(self) -> bool:
+        return self._resolved
+
+    def resolve(self) -> Optional[OnlineResource]:
+        redirect_url = _get_redirect_url(self.url)
+        if redirect_url == self.url:
+            self._resolved = True
+            return self
+
+        meta = {
+            attr.lstrip("_"): getattr(self, attr)
+            for attr in (
+                "file_name",
+                "sha256",
+                "_preprocess",
+                "_loader",
+            )
+        }
+
+        gdrive_id = _get_google_drive_file_id(redirect_url)
+        if gdrive_id:
+            return GDriveResource(gdrive_id, **meta)
+
+        http_resource = HttpResource(redirect_url, **meta)
+        http_resource._resolved = True
+        return http_resource
 
     def _download(self, root: pathlib.Path) -> None:
+        if not self.resolved:
+            return self.resolve()._download(root)
+
         for url in itertools.chain((self.url,), self.mirrors or ()):
             try:
                 download_url(url, str(root), filename=self.file_name, md5=None)

From d47990f82f493ae1d18ae3bd83a08dbfaba67a5c Mon Sep 17 00:00:00 2001
From: Philip Meier <github.pmeier@posteo.de>
Date: Mon, 3 Jan 2022 11:27:18 +0100
Subject: [PATCH 2/3] appease mypy

---
 torchvision/prototype/datasets/utils/_resource.py | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/torchvision/prototype/datasets/utils/_resource.py b/torchvision/prototype/datasets/utils/_resource.py
index 35a0dd210f8..a2643d07747 100644
--- a/torchvision/prototype/datasets/utils/_resource.py
+++ b/torchvision/prototype/datasets/utils/_resource.py
@@ -3,7 +3,7 @@
 import itertools
 import pathlib
 import warnings
-from typing import Optional, Sequence, Tuple, Callable, IO, Any, Union, NoReturn
+from typing import Optional, Sequence, Tuple, Callable, IO, Any, Union, NoReturn, cast
 from urllib.parse import urlparse
 
 from torchdata.datapipes.iter import (
@@ -175,7 +175,7 @@ def resolve(self) -> Optional[OnlineResource]:
 
     def _download(self, root: pathlib.Path) -> None:
         if not self.resolved:
-            return self.resolve()._download(root)
+            return cast(OnlineResource, self.resolve())._download(root)
 
         for url in itertools.chain((self.url,), self.mirrors or ()):
             try:

From c372606b96f80fe57c356f2001110e48715af342 Mon Sep 17 00:00:00 2001
From: Philip Meier <github.pmeier@posteo.de>
Date: Fri, 14 Jan 2022 13:41:45 +0100
Subject: [PATCH 3/3] address review

---
 torchvision/prototype/datasets/utils/_resource.py | 13 ++++++-------
 1 file changed, 6 insertions(+), 7 deletions(-)

diff --git a/torchvision/prototype/datasets/utils/_resource.py b/torchvision/prototype/datasets/utils/_resource.py
index a2643d07747..d7bf9fc4b18 100644
--- a/torchvision/prototype/datasets/utils/_resource.py
+++ b/torchvision/prototype/datasets/utils/_resource.py
@@ -3,7 +3,7 @@
 import itertools
 import pathlib
 import warnings
-from typing import Optional, Sequence, Tuple, Callable, IO, Any, Union, NoReturn, cast
+from typing import Optional, Sequence, Tuple, Callable, IO, Any, Union, NoReturn
 from urllib.parse import urlparse
 
 from torchdata.datapipes.iter import (
@@ -145,11 +145,10 @@ def __init__(
         self.mirrors = mirrors
         self._resolved = False
 
-    @property
-    def resolved(self) -> bool:
-        return self._resolved
+    def resolve(self) -> OnlineResource:
+        if self._resolved:
+            return self
 
-    def resolve(self) -> Optional[OnlineResource]:
         redirect_url = _get_redirect_url(self.url)
         if redirect_url == self.url:
             self._resolved = True
@@ -174,8 +173,8 @@ def resolve(self) -> Optional[OnlineResource]:
         return http_resource
 
     def _download(self, root: pathlib.Path) -> None:
-        if not self.resolved:
-            return cast(OnlineResource, self.resolve())._download(root)
+        if not self._resolved:
+            return self.resolve()._download(root)
 
         for url in itertools.chain((self.url,), self.mirrors or ()):
             try: