`uproot` cannot write root files over xrootd.

[ikrommyd]

To reproduce:

import uproot

file = uproot.recreate("root://cmseos.fnal.gov//store/user/ikrommyd/test/dummy.root")
file["tree"] = {"branch": [1,2,3]}
file.close()

fails with:

OSError                                   Traceback (most recent call last)
Cell In[2], line 1
----> 1 uproot.recreate("root://cmseos.fnal.gov//store/user/ikrommyd/test/dummy.root")

File ~/miniforge3/envs/work/lib/python3.11/site-packages/uproot/writing/writable.py:110, in recreate(file_path, **options)
    106 file_path = uproot._util.regularize_path(file_path)
    107 storage_options = {
    108     key: value for key, value in options.items() if key not in recreate.defaults
    109 }
--> 110 sink = uproot.sink.file.FileSink(file_path, **storage_options)
    111 compression = options.pop("compression", create.defaults["compression"])
    113 initial_directory_bytes = options.pop(
    114     "initial_directory_bytes", create.defaults["initial_directory_bytes"]
    115 )

File ~/miniforge3/envs/work/lib/python3.11/site-packages/uproot/sink/file.py:53, in FileSink.__init__(self, urlpath_or_file_like, **storage_options)
     51 else:
     52     if not self._file_exists(urlpath_or_file_like, **storage_options):
---> 53         self._truncate_file(urlpath_or_file_like, **storage_options)
     55     self._open_file = fsspec.open(
     56         urlpath_or_file_like, mode="r+b", **storage_options
     57     )

File ~/miniforge3/envs/work/lib/python3.11/site-packages/uproot/sink/file.py:81, in FileSink._truncate_file(cls, urlpath, **storage_options)
     79 parent_directory = fs.sep.join(local_path.split(fs.sep)[:-1])
     80 fs.mkdirs(parent_directory, exist_ok=True)
---> 81 fs.touch(local_path, truncate=True)

File ~/miniforge3/envs/work/lib/python3.11/site-packages/fsspec/asyn.py:118, in sync_wrapper.<locals>.wrapper(*args, **kwargs)
    115 @functools.wraps(func)
    116 def wrapper(*args, **kwargs):
    117     self = obj or args[0]
--> 118     return sync(self.loop, func, *args, **kwargs)

File ~/miniforge3/envs/work/lib/python3.11/site-packages/fsspec/asyn.py:103, in sync(loop, func, timeout, *args, **kwargs)
    101     raise FSTimeoutError from return_result
    102 elif isinstance(return_result, BaseException):
--> 103     raise return_result
    104 else:
    105     return return_result

File ~/miniforge3/envs/work/lib/python3.11/site-packages/fsspec/asyn.py:56, in _runner(event, coro, result, timeout)
     54     coro = asyncio.wait_for(coro, timeout=timeout)
     55 try:
---> 56     result[0] = await coro
     57 except Exception as ex:
     58     result[0] = ex

File ~/miniforge3/envs/work/lib/python3.11/site-packages/fsspec_xrootd/xrootd.py:380, in XRootDFileSystem._touch(self, path, truncate, **kwargs)
    376     status, _ = await _async_wrap(self._myclient.truncate)(
    377         path, size=0, timeout=self.timeout
    378     )
    379     if not status.ok:
--> 380         raise OSError(f"File not touched properly: {status.message}")
    381 else:
    382     len = await self._info(path)

OSError: File not touched properly: [ERROR] Server responded with an error: [3013] Unable to truncate (null); Operation not supported

The below reproducers work fine locally but will fail if "dummy" becomes a remote xrootd path.

import awkward as ak
import dask_awkward as dak
import uproot

# Eager
array = ak.Array({"x":[1,2,3], "y":[4,5,6]})
file = uproot.recreate("dummy.root")
file["tree"] = array

# Lazy
x = dak.from_awkward(array, 3)
uproot.dask_write(x, "dummy", prefix="whatever", compute=True)