Handling of URL quoting (for `file://` URLs)

I have a local file at /tmp/URL--https&c%%zenodo.org%record%68331 that I am trying to access via FSSPEC. This fails due to a missing unquoting step, as far as I can tell.

Here is a small demo to show the essence of the issue:

>>> from pathlib import Path
>>> from fsspec.core import url_to_fs

# local file exists
>>> p = Path('/tmp/URL--https&c%%zenodo.org%record%68331')
>>> p.exists()
True

# file:// URL generation via pathlib
>>> p_url = p.as_uri()
# this quotes the URL, which is to be expected
>>> p_url
'file:///tmp/URL--https%26c%25%25zenodo.org%25record%2568331'

# fsspec does not unquote
>>> fs, urlpath = url_to_fs(p_url)
>>> urlpath
'/tmp/URL--https%26c%25%25zenodo.org%25record%2568331'
# the returned urlpath is not the original path
# (this may be OK still)
>>> Path(urlpath).exists()
False

# but fsspec also fails to access the target file
>>> fs.stat(urlpath)
-> FileNotFoundError: [Errno 2] No such file or directory: '/tmp/URL--https%26c%25%25zenodo.org%25record%2568331'

# if quoting is undone, either for the URL, or for the path, things start working
>>> from urllib.parse import unquote
>>> fs.stat(unquote(urlpath))
{'name': '/tmp/URL--https&c%%zenodo.org%record%68331',...}
# or the URL
>>> fs, urlpath = url_to_fs(unquote(p_url))
>>> fs.stat(urlpath)
{'name': '/tmp/URL--https&c%%zenodo.org%record%68331',...}

I was confused by the above behavior, as I expect the urlpath returned by url_to_fs() to match the needs of the simultaneously returned fs object. My expectation was that fsspec would assume all input URL to be adequately quoted, and do any necessary unquoting to match the nature of urlpath to the needs of fs internally.

Do you consider this behavior a bug?

Start by reproducing the example through fsspec.core.url_to_fs() and the returned filesystem's fs.stat() call, comparing quoted and unquoted file:// paths. Trace how the URL path is parsed and passed to the filesystem; done means a pathlib-generated file:// URL resolves to the existing local file without requiring callers to unquote it.