For the arrow S3FileSystem for example, using root_market = "/" throws an error when trying to upload a local file. Love the arrow integration, please let me know if I'm misusing something here.

from pyarrow.fs import S3FileSystem
from fsspec.implementations.arrow import ArrowFSWrapper

fs = ArrowFSWrapper(S3FileSystem())
fs.upload('foo.txt', 'bucket/folder/foo.txt')

Traceback (most recent call last):
File "", line 1, in
File ".../fsspec/spec.py", line 1530, in upload
return self.put(lpath, rpath, recursive=recursive, **kwargs)
File ".../fsspec/spec.py", line 1057, in put
self.put_file(lpath, rpath, **kwargs)
File ".../fsspec/spec.py", line 984, in put_file
self.mkdirs(self._parent(os.fspath(rpath)), exist_ok=True)
File ".../fsspec/spec.py", line 1498, in mkdirs
return self.makedirs(path, exist_ok=exist_ok)
File ".../fsspec/implementations/arrow.py", line 22, in wrapper
return func(*args, **kwargs)
File ".../fsspec/implementations/arrow.py", line 193, in makedirs
self.fs.create_dir(path, recursive=True)
File "pyarrow/_fs.pyx", line 603, in pyarrow._fs.FileSystem.create_dir
File "pyarrow/error.pxi", line 91, in pyarrow.lib.check_status
pyarrow.lib.ArrowInvalid: Path cannot start with a separator ('/bucket/folder')

If I set root_market to '' manually, the upload succeeds

fs.__class__.root_marker = ''
fs.upload('foo.txt', 'bucket/folder/foo.txt')