Align filename prefix splitting with WebDataset library (#7151)

* Align filename prefix splitting with WebDataset library

* Fix import

Author: albertvillanova

src/datasets/packaged_modules/webdataset/webdataset.py

@@ -1,5 +1,6 @@
 import io
 import json
+import re
 from itertools import islice
 from typing import Any, Callable, Dict, List
 
@@ -28,25 +29,26 @@ def _get_pipeline_from_tar(cls, tar_path, tar_iterator):
         fs: fsspec.AbstractFileSystem = fsspec.filesystem("memory")
         streaming_download_manager = datasets.StreamingDownloadManager()
         for filename, f in tar_iterator:
-            if "." in filename:
-                example_key, field_name = filename.split(".", 1)
-                if current_example and current_example["__key__"] != example_key:
-                    yield current_example
-                    current_example = {}
-                current_example["__key__"] = example_key
-                current_example["__url__"] = tar_path
-                current_example[field_name.lower()] = f.read()
-                if field_name.split(".")[-1] in SINGLE_FILE_COMPRESSION_EXTENSION_TO_PROTOCOL:
-                    fs.write_bytes(filename, current_example[field_name.lower()])
-                    extracted_file_path = streaming_download_manager.extract(f"memory://{filename}")
-                    with fsspec.open(extracted_file_path) as f:
-                        current_example[field_name.lower()] = f.read()
-                    fs.delete(filename)
-                    data_extension = xbasename(extracted_file_path).split(".")[-1]
-                else:
-                    data_extension = field_name.split(".")[-1]
-                if data_extension in cls.DECODERS:
-                    current_example[field_name] = cls.DECODERS[data_extension](current_example[field_name])
+            example_key, field_name = base_plus_ext(filename)
+            if example_key is None:
+                continue
+            if current_example and current_example["__key__"] != example_key:
+                yield current_example
+                current_example = {}
+            current_example["__key__"] = example_key
+            current_example["__url__"] = tar_path
+            current_example[field_name.lower()] = f.read()
+            if field_name.split(".")[-1] in SINGLE_FILE_COMPRESSION_EXTENSION_TO_PROTOCOL:
+                fs.write_bytes(filename, current_example[field_name.lower()])
+                extracted_file_path = streaming_download_manager.extract(f"memory://{filename}")
+                with fsspec.open(extracted_file_path) as f:
+                    current_example[field_name.lower()] = f.read()
+                fs.delete(filename)
+                data_extension = xbasename(extracted_file_path).split(".")[-1]
+            else:
+                data_extension = field_name.split(".")[-1]
+            if data_extension in cls.DECODERS:
+                current_example[field_name] = cls.DECODERS[data_extension](current_example[field_name])
         if current_example:
             yield current_example
 
@@ -121,6 +123,18 @@ def _generate_examples(self, tar_paths, tar_iterators):
                 yield f"{tar_idx}_{example_idx}", example
 
 
+# Source: https://github.com/webdataset/webdataset/blob/87bd5aa41602d57f070f65a670893ee625702f2f/webdataset/tariterators.py#L25
+def base_plus_ext(path):
+    """Split off all file extensions.
+
+    Returns base, allext.
+    """
+    match = re.match(r"^((?:.*/|)[^.]+)[.]([^/]*)$", path)
+    if not match:
+        return None, None
+    return match.group(1), match.group(2)
+
+
 # Obtained with:
 # ```
 # import PIL.Image