fix handling of broken file references in brainvisionrawio

Author: chkothe

neo/rawio/brainvisionrawio.py

@@ -55,6 +55,9 @@ def _parse_header(self):
         marker_filename = self.filename.replace(bname, vhdr_header["Common Infos"]["MarkerFile"])
         binary_filename = self.filename.replace(bname, vhdr_header["Common Infos"]["DataFile"])
 
+        binary_filename = self._ensure_filename(binary_filename, "binary")
+        marker_filename = self._ensure_filename(marker_filename, "marker")
+
         if vhdr_header["Common Infos"]["DataFormat"] != "BINARY":
             raise NeoReadWriteError(
                 f"Only `BINARY` format has been implemented. Current Data Format is {vhdr_header['Common Infos']['DataFormat']}"
@@ -236,6 +239,25 @@ def _rescale_event_timestamp(self, event_timestamps, dtype, event_channel_index)
     def _get_analogsignal_buffer_description(self, block_index, seg_index, buffer_id):
         return self._buffer_descriptions[block_index][seg_index][buffer_id]
 
+    def _ensure_filename(self, filename, kind):
+        if not os.path.exists(filename):
+            # file not found, subsequent import stage would fail
+            ext = os.path.splitext(filename)[1]
+            # Check if we can fall back to a file with the same prefix as the .vhdr.
+            # This can happen when users rename their files but forget to edit the
+            # .vhdr file to fix the path reference to the binary and marker files,
+            # in which case import will fail. These files come in triples, like:
+            # myfile.vhdr, myfile.eeg and myfile.vmrk; this code will thus pick
+            # the next best alternative.
+            alt_name = self.filename.replace(".vhdr", ext)
+            if os.path.exists(alt_name):
+                self.logger.warning(
+                    f"The {kind} file {filename} was not found, but found a file whose "
+                    f"prefix matched the .vhdr ({os.path.basename(alt_name)}). Using "
+                    f"this file instead.")
+                filename = alt_name
+        return filename
+
 
 def read_brainvsion_soup(filename):
     with open(filename, "r", encoding="utf8") as f: