write_raw_bids cannot find emptyroom when anonymize=True

[drammock]

Description of the problem

calling write_raw_bids(..., anonymize=dict(daysback=<some_positive_integer>), empty_room=<some_Raw_object>) fails, because the ERM will be written at sub-emptyroom/ses-<some_date_far_in_the_past>, but the subsequent call to actually write the Raw data file will try to find the empty room based on the value of the ERM's BidsPath before anonymization.

I think the culprit is basically this line:

mne-bids/mne_bids/write.py

Line 1831 in 313fe10

associated_er_path = er_bids_path.fpath

Steps to reproduce

In [1]: import mne
In [2]: from mne_bids import write_raw_bids, BIDSPath
In [3]: fdir = mne.datasets.sample.data_path()
In [4]: fpath = (fdir / 'MEG' / 'sample' / 'sample_audvis_raw.fif')
In [5]: raw = mne.io.read_raw(fpath, preload=False, verbose=False)
In [6]: erm = raw.copy()  # fake ERM just for demo purposes
In [7]: bp = BIDSPath(subject="sample", root=".", task="foo")
In [8]: write_raw_bids(raw=raw, empty_room=erm, bids_path=bp, anonymize=dict(daysback=23456))

Expected results

writing succeeds

Actual results

Here's the output and traceback

<ipython-input-8-84bb36779bc7>:1: RuntimeWarning: `daysback` is too small; the measurement date is after 1925, which is not recommended by BIDS.The minimum `daysback` value for changing the measurement date of this data to before this date is 28461
  write_raw_bids(raw=raw, empty_room=erm, bids_path=bp, anonymize=dict(daysback=23456))
Writing './README'...
Writing './participants.tsv'...
Writing 'participants.json'...
Writing of electrodes.tsv is not supported for data type "meg". Skipping ...
Writing './dataset_description.json'...
Writing 'sub-emptyroom/ses-19380914/meg/sub-emptyroom_ses-19380914_task-noise_meg.json'...
Writing 'sub-emptyroom/ses-19380914/meg/sub-emptyroom_ses-19380914_task-noise_channels.tsv'...
Copying data files to sub-emptyroom_ses-19380914_task-noise_meg.fif
Reserving possible split file sub-emptyroom_ses-19380914_task-noise_split-01_meg.fif
Writing /home/drmccloy/sub-emptyroom/ses-19380914/meg/sub-emptyroom_ses-19380914_task-noise_meg.fif
Closing /home/drmccloy/sub-emptyroom/ses-19380914/meg/sub-emptyroom_ses-19380914_task-noise_meg.fif
[done]
Writing 'sub-emptyroom/ses-19380914/sub-emptyroom_ses-19380914_scans.tsv'...
Wrote sub-emptyroom/ses-19380914/sub-emptyroom_ses-19380914_scans.tsv entry with meg/sub-emptyroom_ses-19380914_task-noise_meg.fif.
---------------------------------------------------------------------------
FileNotFoundError                         Traceback (most recent call last)
Cell In[8], line 1
----> 1 write_raw_bids(raw=raw, empty_room=erm, bids_path=bp, anonymize=dict(daysback=23456))

File <decorator-gen-447>:12, in write_raw_bids(raw, bids_path, events, event_id, anonymize, format, symlink, empty_room, allow_preload, montage, acpc_aligned, overwrite, events_data, verbose)

File /opt/mne/bids/mne_bids/write.py:1854, in write_raw_bids(raw, bids_path, events, event_id, anonymize, format, symlink, empty_room, allow_preload, montage, acpc_aligned, overwrite, events_data, verbose)
   1852 if associated_er_path is not None:
   1853     if not associated_er_path.exists():
-> 1854         raise FileNotFoundError(
   1855             f"Empty-room data file not found: " f"{associated_er_path}"
   1856         )
   1858     # Turn it into a path relative to the BIDS root
   1859     associated_er_path = Path(
   1860         str(associated_er_path).replace(str(bids_path.root), "")
   1861     )

FileNotFoundError: Empty-room data file not found: sub-emptyroom/ses-20021203/meg/sub-emptyroom_ses-20021203_task-noise_meg.fif

Additional information

$ mne sys_info
Platform             Linux-5.15.0-58-generic-x86_64-with-glibc2.35
Python               3.11.7 | packaged by conda-forge | (main, Dec 23 2023, 14:43:09) [GCC 12.3.0]
Executable           /opt/mambaforge/envs/mnedev/bin/python3.11
CPU                  x86_64 (16 cores)
Memory               125.7 GB

Core
├☒ mne               1.7.0.dev76+g52a905928 (outdated, release 1.7.1 is available!)
├☑ numpy             1.26.4 (OpenBLAS 0.3.23.dev with 16 threads)
├☑ scipy             1.11.4
└☑ matplotlib        3.8.2 (backend=QtAgg)

Numerical (optional)
├☑ sklearn           1.3.2
├☑ numba             0.58.1
├☑ nibabel           5.2.0
├☑ nilearn           0.10.2
├☑ dipy              1.9.0
├☑ openmeeg          2.5.7
├☑ cupy              13.0.0
├☑ pandas            2.1.4
├☑ h5io              0.2.1
└☑ h5py              3.10.0

Visualization (optional)
├☑ pyvista           0.43.2 (OpenGL 4.5.0 NVIDIA 545.23.08 via NVIDIA GeForce RTX 2060/PCIe/SSE2)
├☑ pyvistaqt         0.11.0
├☑ vtk               9.3.0
├☑ qtpy              2.4.1 (PyQt6=6.6.0)
├☑ ipympl            0.9.3
├☑ pyqtgraph         0.13.3
├☑ mne-qt-browser    0.7.0.dev9+g547b976
├☑ ipywidgets        8.1.1
├☑ trame_client      2.14.2
├☑ trame_server      2.15.0
├☑ trame_vtk         2.7.0
└☑ trame_vuetify     2.3.1

Ecosystem (optional)
├☑ mne-bids          0.15.0.dev24+g05b8e6b8
├☑ mne-nirs          0.7.0.dev0
├☑ mne-connectivity  0.7.0.dev0
├☑ mne-bids-pipeline 1.6.0.dev8+g9055e9c
├☑ neo               0.13.0
├☑ eeglabio          0.0.2-4
├☑ edfio             0.4.0
├☑ mffpy             0.8.0
├☑ pybv              0.7.5
└☐ unavailable       mne-features, mne-icalabel

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