MRG: Better split file handling in Report.parse_folder()

doc/changes/latest.inc

@@ -103,6 +103,8 @@ Bugs
 
 - Attempting to remove baseline correction from preloaded `~mne.Epochs` will now raise an exception by `Richard Höchenberger`_ (:gh:`8435`)
 
+- :meth:`mne.Report.parse_folder` will now correctly handle split FIFF files by `Richard Höchenberger`_ (:gh:`8486`)
+
 API changes
 ~~~~~~~~~~~
 

mne/report.py

@@ -1456,6 +1456,30 @@ class construction.
         for p in pattern:
             fnames.extend(sorted(_recursive_search(self.data_path, p)))
 
+        if not fnames and not render_bem:
+            raise RuntimeError(f'No matching files found in {self.data_path}')
+
+        # For split files, only keep the first one.
+        fnames_to_remove = []
+        for fname in fnames:
+            if _endswith(fname, ('raw', 'sss', 'meg')):
+                inst = read_raw_fif(fname, allow_maxshield=True, preload=False)
+            elif _endswith(fname, ('epo',)):
+                inst = read_epochs(fname, preload=False)
+            elif _endswith(fname, ('ave',)):
+                inst = read_evokeds(fname, condition=0, allow_maxshield=True)
+            else:
+                continue
+
+            if len(inst.filenames) > 1:
+                fnames_to_remove.extend(inst.filenames[1:])
+
+        fnames_to_remove = list(set(fnames_to_remove))  # Drop duplicates
+        for fname in fnames_to_remove:
+            if fname in fnames:
+                del fnames[fnames.index(fname)]
+        del fnames_to_remove
+
         if self.info_fname is not None:
             info = read_info(self.info_fname, verbose=False)
             sfreq = info['sfreq']

mne/tests/test_report.py

@@ -296,7 +296,8 @@ def test_render_mri_without_bem(tmpdir):
     shutil.copyfile(mri_fname, op.join(tempdir, 'sample', 'mri', 'T1.mgz'))
     report = Report(info_fname=raw_fname,
                     subject='sample', subjects_dir=tempdir)
-    report.parse_folder(tempdir, render_bem=False)
+    with pytest.raises(RuntimeError, match='No matching files found'):
+        report.parse_folder(tempdir, render_bem=False)
     with pytest.warns(RuntimeWarning, match='No BEM surfaces found'):
         report.parse_folder(tempdir, render_bem=True, mri_decim=20)
     assert 'bem' in report.fnames
@@ -495,4 +496,18 @@ def test_scraper(tmpdir):
     assert op.isfile(img_fname.replace('png', 'svg'))
 
 
+@pytest.mark.parametrize('split_naming', ('neuromag', 'bids',))
+def test_split_files(tmpdir, split_naming):
+    """Test that in the case of split files, we only parse the first."""
+    raw = read_raw_fif(raw_fname)
+    split_size = '7MB'  # Should produce 3 files
+    buffer_size_sec = 1  # Tiny buffer so it's smaller than the split size
+    raw.save(op.join(tmpdir, 'raw_meg.fif'), split_size=split_size,
+             split_naming=split_naming, buffer_size_sec=buffer_size_sec)
+
+    report = Report()
+    report.parse_folder(tmpdir, render_bem=False)
+    assert len(report.fnames) == 1
+
+
 run_tests_if_main()