Make Resource.url a property.

PiperOrigin-RevId: 681063729

Author: fineguy

tensorflow_datasets/core/download/download_manager.py

@@ -372,7 +372,6 @@ def _download_or_get_cache(
     if not isinstance(resource, resource_lib.Resource):
       resource = resource_lib.Resource(url=resource)
     url = resource.url
-    assert url is not None, 'URL is undefined from resource.'
 
     expected_url_info = self._url_infos.get(url)
     if (
@@ -406,7 +405,7 @@ def _download_or_get_cache(
       return self._download(resource)
 
     # Download has been cached (checksum known)
-    elif expected_url_info and resource_lib.Resource.exists_locally(
+    elif expected_url_info and resource_lib.is_locally_cached(
         checksum_path := self._get_dl_path(resource, expected_url_info.checksum)
     ):
       self._register_or_validate_checksums(
@@ -420,7 +419,7 @@ def _download_or_get_cache(
       return promise.Promise.resolve(checksum_path)
 
     # Download has been cached (checksum unknown)
-    elif resource_lib.Resource.exists_locally(
+    elif resource_lib.is_locally_cached(
         url_path := self._get_dl_path(resource)
     ):
       computed_url_info = downloader.read_url_info(url_path)
@@ -458,7 +457,7 @@ def _register_or_validate_checksums(
       computed_url_info: checksums.UrlInfo,
   ) -> epath.Path | None:
     """Validates/records checksums and returns checksum path if registered."""
-    url: str = resource.url  # pytype: disable=annotation-type-mismatch
+    url = resource.url
 
     if self._register_checksums:
       # Note:
@@ -517,7 +516,7 @@ def _download(
       Promise of the path to the downloaded url.
     """
     url_path = self._get_dl_path(resource)
-    url: str = resource.url  # pytype: disable=annotation-type-mismatch
+    url = resource.url
 
     # Download in a tmp directory next to url_path (to avoid name collisions)
     # `download_tmp_dir` is cleaned-up in `callback`

tensorflow_datasets/core/download/resource.py

@@ -197,6 +197,12 @@ def get_info_path(path: epath.Path) -> epath.Path:
   return path.with_suffix(path.suffix + '.INFO')
 
 
+def is_locally_cached(path: epath.Path) -> bool:
+  """Returns whether the path is locally cached."""
+  # If INFO file doesn't exist, consider path NOT cached.
+  return path.exists() and get_info_path(path).exists()
+
+
 def _read_info(info_path: epath.Path) -> Json:
   """Returns info dict."""
   if not info_path.exists():
@@ -298,19 +304,19 @@ def __init__(
       relative_download_dir: Optional directory for downloading relative to
         `download_dir`.
     """
-    self.url = url
+    self._url = url
     self._extract_method = extract_method
     self.path: epath.Path = epath.Path(path) if path else None  # pytype: disable=annotation-type-mismatch  # attribute-variable-annotations
     self.relative_download_dir = relative_download_dir
 
-  @classmethod
-  def exists_locally(cls, path: epath.Path) -> bool:
-    """Returns whether the resource exists locally, at `resource.path`."""
-    # If INFO file doesn't exist, consider resource does NOT exist, as it would
-    # prevent guessing the `extract_method`.
-    return path.exists() and get_info_path(path).exists()
+  @property
+  def url(self) -> str:
+    """Returns the URL at which to download the resource."""
+    if not self._url:
+      raise ValueError('URL is undefined from resource.')
+    return self._url
 
   @property
   def extract_method(self) -> ExtractMethod:
-    """Returns `ExtractMethod` to use on resource. Cannot be None."""
+    """Returns `ExtractMethod` to use on resource."""
     return self._extract_method or _get_extract_method(self.path)

tensorflow_datasets/testing/dataset_builder_testing.py

@@ -315,8 +315,8 @@ def _get_dl_extract_result(self, url):
     return self._prepare_download_results(self.DL_EXTRACT_RESULT)
 
   def _get_dl_extract_only_result(self, url):
+    del url
     if self.DL_EXTRACT_ONLY_RESULT:
-      tf.nest.map_structure(self._add_url, url)
       return self._prepare_download_results(self.DL_EXTRACT_ONLY_RESULT)
 
   def _get_dl_download_result(self, url):