xPath cannot handle hdfs:///xxxx properly

[li-yi-dong]

Describe the bug

_as_str('hdfs:///xxxx') would return hdfs://xxxx. Removing one / and making the path invalid.

For the use case like

ds = load_dataset(
    "parquet",
    data_files={
        "train": "hdfs:///user/path/to/data/train*.parquet",
    },
    streaming=True,
    storage_options={
        "host": "hostname",  
    }
)

would get

  File "/usr/local/lib/python3.11/site-packages/datasets/load.py", line 1511, in load_dataset
    return builder_instance.as_streaming_dataset(split=split)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/datasets/builder.py", line 1193, in as_streaming_dataset
    splits_generators = {sg.name: sg for sg in self._split_generators(dl_manager)}
                                               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/datasets/packaged_modules/parquet/parquet.py", line 123, in _split_generators
    with open(file, "rb") as f:
         ^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/datasets/streaming.py", line 73, in wrapper
    return function(*args, download_config=download_config, **kwargs)
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/datasets/utils/file_utils.py", line 963, in xopen
    file_obj = fsspec.open(file, mode=mode, *args, **kwargs).open()
               ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/fsspec/core.py", line 508, in open
    out = open_files(
          ^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/fsspec/core.py", line 295, in open_files
    fs, fs_token, paths = get_fs_token_paths(
                          ^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/fsspec/core.py", line 672, in get_fs_token_paths
    chain = _un_chain(urlpath0, storage_options or {})
            ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/local/lib/python3.11/site-packages/fsspec/core.py", line 365, in _un_chain
    kw = dict(
         ^^^^^
TypeError: dict() got multiple values for keyword argument 'host'

Due to the file passed to fsspec.open is hdfs://user/path/to/data/trainxxx.parquet, and fsspec would take user as the hostname

Steps to reproduce the bug

Expected behavior

Keep all three /

Environment info

datasets 4.4.2