Allow classes to register extensions with opener functions; use this for .mgz. Remove .mgz-specific logic from BinOpener, and deprecate.

Author: Ben Cipollini

nibabel/freesurfer/mghformat.py

@@ -18,6 +18,7 @@
 from ..fileholders import FileHolder,  copy_file_map
 from ..arrayproxy import ArrayProxy
 from ..keywordonly import kw_only_meth
+from ..openers import Opener
 
 # mgh header
 # See https://surfer.nmr.mgh.harvard.edu/fswiki/FsTutorial/MghFormat
@@ -453,6 +454,7 @@ def writeftr_to(self, fileobj):
         fileobj.write(ftr_nd.tostring())
 
 
+@Opener.register_extension('.mgz', Opener.gz_def)
 class MGHImage(SpatialImage):
     """ Class for MGH format image
     """

nibabel/openers.py

@@ -146,3 +146,13 @@ def __enter__(self):
 
     def __exit__(self, exc_type, exc_val, exc_tb):
         self.close_if_mine()
+
+    @classmethod
+    def register_extension(opener_klass, ext, func):
+        """Decorator"""
+        def decorate(klass):
+            assert ext not in opener_klass.compress_ext_map, \
+                "Cannot redefine extension-function mappings."
+            opener_klass.compress_ext_map[ext] = func
+            return klass
+        return decorate

nibabel/volumeutils.py

@@ -1537,10 +1537,16 @@ def rec2dict(rec):
 
 
 class BinOpener(Opener):
-    # Adds .mgz as gzipped file name type
+    """ Deprecated class that used to handle .mgz 
+    through specialized logic."""
     __doc__ = Opener.__doc__
-    compress_ext_map = Opener.compress_ext_map.copy()
-    compress_ext_map['.mgz'] = Opener.gz_def
+
+    def __init__(self, *args, **kwargs):
+        warnings.warn("Please use %s class instead of %s" % (
+                          Opener.__class__.__name__,
+                          self.__class__.__name__),
+                      DeprecationWarning, stacklevel=2)
+        return super(BinOpener, self).__init__(*args, **kwargs)
 
 
 def fname_ext_ul_case(fname):