Skip download and prepare if the dataset is already prepared and download_mode is REUSE_DATASET_IF_EXISTS.

PiperOrigin-RevId: 642267366

Author: tomvdw

tensorflow_datasets/core/load.py

@@ -43,6 +43,7 @@
 from tensorflow_datasets.core import utils
 from tensorflow_datasets.core import visibility
 from tensorflow_datasets.core.dataset_builders import huggingface_dataset_builder  # pylint:disable=unused-import
+from tensorflow_datasets.core.download import util
 from tensorflow_datasets.core.utils import error_utils
 from tensorflow_datasets.core.utils import gcs_utils
 from tensorflow_datasets.core.utils import py_utils
@@ -501,6 +502,16 @@ def _download_and_prepare_builder(
     download: bool,
     download_and_prepare_kwargs: Optional[Dict[str, Any]],
 ) -> None:
+  """Downloads and prepares the dataset builder if necessary."""
+  if dbuilder.is_prepared():
+    if not download_and_prepare_kwargs:
+      return
+    if download_config := download_and_prepare_kwargs.get('download_config'):
+      if (
+          download_config.download_mode
+          == util.GenerateMode.REUSE_DATASET_IF_EXISTS
+      ):
+        return
   if download:
     download_and_prepare_kwargs = download_and_prepare_kwargs or {}
     dbuilder.download_and_prepare(**download_and_prepare_kwargs)
@@ -663,7 +674,7 @@ def load(
 
 
 def _set_file_format_for_data_source(
-    builder_kwargs: Optional[Dict[str, Any]]
+    builder_kwargs: Optional[Dict[str, Any]],
 ) -> Dict[str, Any]:
   """Normalizes file format in builder_kwargs for `tfds.data_source`."""
   if builder_kwargs is None:

tensorflow_datasets/core/registered_test.py

@@ -17,10 +17,8 @@
 
 import abc
 import re
-
 from unittest import mock
 import pytest
-
 from tensorflow_datasets import testing
 from tensorflow_datasets.core import constants
 from tensorflow_datasets.core import load
@@ -49,6 +47,9 @@ def as_dataset(self, **kwargs):
     self.as_dataset_kwargs = kwargs
     return self
 
+  def is_prepared(self) -> bool:
+    return False
+
   VERSION = utils.Version("1.0.0")
   BUILDER_CONFIGS = []
   builder_configs = {}