Fix bad config ids that name cache directories

src/datasets/builder.py

@@ -123,6 +123,8 @@ def create_config_id(
         # it was previously ignored before the introduction of config id because we didn't want
         # to change the config name. Now it's fine to take it into account for the config id.
         # config_kwargs_to_add_to_suffix.pop("data_dir", None)
+        if "data_dir" in config_kwargs_to_add_to_suffix and config_kwargs_to_add_to_suffix["data_dir"] is None:
+            del config_kwargs_to_add_to_suffix["data_dir"]
         if config_kwargs_to_add_to_suffix:
             # we don't care about the order of the kwargs
             config_kwargs_to_add_to_suffix = {

tests/test_builder.py

@@ -1,6 +1,7 @@
 import os
 import tempfile
 import types
+from pathlib import Path
 from unittest import TestCase
 
 import numpy as np
@@ -518,6 +519,12 @@ def test_generator_based_download_and_prepare(self):
                 )
             )
 
+    def test_cache_dir_no_args(self):
+        with tempfile.TemporaryDirectory() as tmp_dir:
+            dummy_builder = DummyGeneratorBasedBuilder(cache_dir=tmp_dir, name="dummy", data_dir=None, data_files=None)
+            relative_cache_dir_parts = Path(dummy_builder._relative_data_dir()).parts
+            self.assertEqual(relative_cache_dir_parts, ("dummy_generator_based_builder", "dummy", "0.0.0"))
+
     def test_cache_dir_for_data_files(self):
         with tempfile.TemporaryDirectory() as tmp_dir:
             dummy_data1 = os.path.join(tmp_dir, "dummy_data1.txt")