load after close automatically reopens, but doesn't close everything

What happened?

Calling .close, then .load works, and keeps the file closed (so it can be overwritten or removed). However, it doesn't work if e.g. a copy is made. The file is apparently kept in an open state by the copy.

(Apologies in advance if this is a duplicate, I've searched for load and close, but it yields many many results; #4131 is topical, but is closed.)

What did you expect to happen?

Either loading after close should raise an error (see #4131), or the file should be closed consistently, everywhere.

Currently, it's somewhat easy to accidentally end up in a situation where there's no way to close a file.
Because the first .close() sets the ._close attribute to None, there doesn't seem to be a way to get it back, unless you've stored a reference to it beforehand -- see the workaround below.

Minimal Complete Verifiable Example

# This'll run without a problem:

import xarray as xr
import os

path = "tmp1.nc"
xr.Dataset({"var1": ("x", [1, 2, 3])}).to_netcdf(path)
ds = xr.open_dataset(path)
ds.close()
ds.load()
os.remove(path)

# This errors:

path = "tmp2.nc"
xr.Dataset({"var1": ("x", [1, 2, 3])}).to_netcdf(path)
ds = xr.open_dataset(path)
ds2 = ds.copy()
ds.close()
ds.load()
ds.close()  # does nothing since ds._close is currently None
ds2.close()  # does nothing
os.remove(path)  # PermissionError

# Workaround

path = "tmp3.nc"
xr.Dataset({"var1": ("x", [1, 2, 3])}).to_netcdf(path)
ds = xr.open_dataset(path)
close_func = ds._close
ds2 = ds.copy()
ds.close()
ds.load()
close_func()
os.remove(path)

MVCE confirmation

• Minimal example — the example is as focused as reasonably possible to demonstrate the underlying issue in xarray.
• Complete example — the example is self-contained, including all data and the text of any traceback.
• Verifiable example — the example copy & pastes into an IPython prompt or Binder notebook, returning the result.
• New issue — a search of GitHub Issues suggests this is not a duplicate.
• Recent environment — the issue occurs with the latest version of xarray and its dependencies.

Relevant log output

Anything else we need to know?

No response

Environment

INSTALLED VERSIONS
------------------
commit: None
python: 3.12.8 | packaged by conda-forge | (main, Dec  5 2024, 14:06:27) [MSC v.1942 64 bit (AMD64)]
python-bits: 64
OS: Windows
OS-release: 11
machine: AMD64
processor: Intel64 Family 6 Model 191 Stepping 2, GenuineIntel
byteorder: little
LC_ALL: None
LANG: None
LOCALE: ('Dutch_Netherlands', '1252')
libhdf5: 1.14.4
libnetcdf: 4.9.2

xarray: 2025.1.2
pandas: 2.2.3
numpy: 2.1.3
scipy: 1.15.1
netCDF4: 1.7.2
pydap: None
h5netcdf: None
h5py: None
zarr: 3.0.2
cftime: 1.6.4
nc_time_axis: None
iris: None
bottleneck: None
dask: 2025.1.0
distributed: 2025.1.0
matplotlib: 3.10.0
cartopy: None
seaborn: None
numbagg: None
fsspec: 2025.2.0
cupy: None
pint: None
sparse: None
flox: None
numpy_groupies: None
setuptools: 75.8.0
pip: 25.0
conda: None
pytest: 8.3.4
mypy: None
IPython: 8.32.0
sphinx: 8.1.3

Start by reproducing the two Python examples around xarray.open_dataset and Dataset.close, load, and copy. Trace how the copied Dataset retains the file handle, then determine whether loading after close should raise or close all references consistently. Done means the chosen behavior is covered and the copied dataset no longer prevents os.remove(path).