RF: Subclass Cifti2MetaData from CaretMetaData and add API compatibility hacks

Author: effigies

nibabel/cifti2/cifti2.py

@@ -25,6 +25,7 @@
 from ..nifti1 import Nifti1Extensions
 from ..nifti2 import Nifti2Image, Nifti2Header
 from ..arrayproxy import reshape_dataobj
+from ..caret import CaretMetaData
 from warnings import warn
 
 
@@ -102,7 +103,7 @@ def _underscore(string):
     return re.sub(r'([a-z0-9])([A-Z])', r'\1_\2', string).lower()
 
 
-class Cifti2MetaData(xml.XmlSerializable, MutableMapping):
+class Cifti2MetaData(CaretMetaData):
     """ A list of name-value pairs
 
     * Description - Provides a simple method for user-supplied metadata that
@@ -121,25 +122,27 @@ class Cifti2MetaData(xml.XmlSerializable, MutableMapping):
     ----------
     data : list of (name, value) tuples
     """
-    def __init__(self, metadata=None):
-        self.data = OrderedDict()
-        if metadata is not None:
-            self.update(metadata)
+    def __init__(self, *args, **kwargs):
+        if not args and list(kwargs) == ["metadata"]:
+            md = kwargs.pop("metadata")
+            if not isinstance(md, str):
+                warn("CaretMetaData now has a dict-like interface and will "
+                     "no longer accept the ``metadata`` keyword argument in "
+                     "NiBabel 6.0. See ``pydoc dict`` for initialization options.",
+                     FutureWarning, stacklevel=2)
+                if md is not None:
+                    args = (md,)
+        if args == (None,):
+            warn("CaretMetaData now has a dict-like interface and will no longer "
+                 "accept the positional argument ``None`` in NiBabel 6.0. "
+                 "See ``pydoc dict`` for initialization options.",
+                 FutureWarning, stacklevel=2)
+            args = ()
+        super().__init__(*args, **kwargs)
 
-    def __getitem__(self, key):
-        return self.data[key]
-
-    def __setitem__(self, key, value):
-        self.data[key] = value
-
-    def __delitem__(self, key):
-        del self.data[key]
-
-    def __len__(self):
-        return len(self.data)
-
-    def __iter__(self):
-        return iter(self.data)
+    @property
+    def data(self):
+        return self._data
 
     def difference_update(self, metadata):
         """Remove metadata key-value pairs
@@ -159,17 +162,6 @@ def difference_update(self, metadata):
         for k in pairs:
             del self.data[k]
 
-    def _to_xml_element(self):
-        metadata = xml.Element('MetaData')
-
-        for name_text, value_text in self.data.items():
-            md = xml.SubElement(metadata, 'MD')
-            name = xml.SubElement(md, 'Name')
-            name.text = str(name_text)
-            value = xml.SubElement(md, 'Value')
-            value.text = str(value_text)
-        return metadata
-
 
 class Cifti2LabelTable(xml.XmlSerializable, MutableMapping):
     r""" CIFTI-2 label table: a sequence of ``Cifti2Label``\s

nibabel/cifti2/cifti2_axes.py

@@ -1075,7 +1075,6 @@ def to_mapping(self, dim):
         """
         mim = cifti2.Cifti2MatrixIndicesMap([dim], 'CIFTI_INDEX_TYPE_SCALARS')
         for name, meta in zip(self.name, self.meta):
-            meta = None if len(meta) == 0 else meta
             named_map = cifti2.Cifti2NamedMap(name, cifti2.Cifti2MetaData(meta))
             mim.append(named_map)
         return mim
@@ -1213,8 +1212,6 @@ def to_mapping(self, dim):
             label_table = cifti2.Cifti2LabelTable()
             for key, value in label.items():
                 label_table[key] = (value[0],) + tuple(value[1])
-            if len(meta) == 0:
-                meta = None
             named_map = cifti2.Cifti2NamedMap(name, cifti2.Cifti2MetaData(meta),
                                               label_table)
             mim.append(named_map)