Mandatorily wrap _read_chunk in a check_chunk_n decorator

strax/storage/common.py

@@ -403,6 +403,13 @@ class StorageBackend:
     these have to be hardcoded (or made part of the key).
     """
 
+    def __new__(cls, *args, **kwargs):
+        """Mandatorily wrap _read_chunk in a check_chunk_n decorator"""
+        if '_read_chunk' in cls.__dict__:
+            method = getattr(cls, '_read_chunk')
+            setattr(cls, '_read_chunk', strax.check_chunk_n(method))
+        return super(StorageBackend, cls).__new__(cls)
+
     def loader(self,
                backend_key,
                time_range=None,

strax/storage/files.py

@@ -251,7 +251,6 @@ def _read_and_format_chunk(self, *args, **kwargs):
             chunk.target_size_mb = self.set_chunk_size_mb
         return chunk
 
-    @strax.check_chunk_n
     def _read_chunk(self, dirname, chunk_info, dtype, compressor):
         fn = osp.join(dirname, chunk_info['filename'])
         return strax.load_file(fn, dtype=dtype, compressor=compressor)

strax/storage/mongo.py

@@ -45,7 +45,6 @@ def __init__(self, uri: str, database: str, col_name: str):
         self._buff_mb = DEFAULT_MONGO_BACKEND_BUFFER_MB
         self._buff_nruns = DEFAULT_MONGO_BACKEND_BUFFER_NRUNS
 
-    @strax.check_chunk_n
     def _read_chunk(self, backend_key, chunk_info, dtype, compressor):
         """See strax.Backend"""
         chunk_i = chunk_info["chunk_i"]

strax/storage/zipfiles.py

@@ -104,8 +104,6 @@ def zip_dir(input_dir, output_zipfile, delete=False):
 
 @export
 class ZipFileBackend(strax.StorageBackend):
-
-    @strax.check_chunk_n
     def _read_chunk(self, zipn_and_dirn, chunk_info, dtype, compressor):
         zipn, dirn = zipn_and_dirn
         with zipfile.ZipFile(zipn) as zp: