RF: Change ArrayProxy.order class var to _default_order, deprecate order

Author: effigies

nibabel/arrayproxy.py

@@ -27,6 +27,7 @@
 """
 from contextlib import contextmanager
 from threading import RLock
+import warnings
 
 import numpy as np
 
@@ -83,7 +84,7 @@ class ArrayProxy:
     See :mod:`nibabel.minc1`, :mod:`nibabel.ecat` and :mod:`nibabel.parrec` for
     examples.
     """
-    order = 'F'
+    _default_order = 'F'
 
     def __init__(self, file_like, spec, *, mmap=True, order=None, keep_file_open=None):
         """Initialize array proxy instance
@@ -147,13 +148,25 @@ def __init__(self, file_like, spec, *, mmap=True, order=None, keep_file_open=Non
         else:
             raise TypeError('spec must be tuple of length 2-5 or header object')
 
+        # Warn downstream users that the class variable order is going away
+        if hasattr(self.__class__, 'order'):
+            warnings.warn(f'Class {self.__class__} has an `order` class variable. '
+                          'ArrayProxy subclasses should rename this variable to `_default_order` '
+                          'to avoid conflict with instance variables.\n'
+                          '* deprecated in version: 5.0\n'
+                          '* will raise error in version: 7.0\n',
+                          DeprecationWarning, stacklevel=2)
+            # Override _default_order with order, to follow intent of subclasser
+            self._default_order = self.order
+
         # Copies of values needed to read array
         self._shape, self._dtype, self._offset, self._slope, self._inter = par
         # Permit any specifier that can be interpreted as a numpy dtype
         self._dtype = np.dtype(self._dtype)
         self._mmap = mmap
-        if order is not None:
-            self.order = order
+        if order is None:
+            order = self._default_order
+        self.order = order
         # Flags to keep track of whether a single ImageOpener is created, and
         # whether a single underlying file handle is created.
         self._keep_file_open, self._persist_opener = \

nibabel/tests/test_arrayproxy.py

@@ -15,13 +15,16 @@
 
 import pickle
 from io import BytesIO
+from packaging.version import Version
 from ..tmpdirs import InTemporaryDirectory
 
 import numpy as np
 
+from .. import __version__
 from ..arrayproxy import (ArrayProxy, is_proxy, reshape_dataobj, get_obj_dtype)
 from ..openers import ImageOpener
 from ..nifti1 import Nifti1Header
+from ..deprecator import ExpiredDeprecationError
 
 from unittest import mock
 
@@ -57,6 +60,10 @@ def copy(self):
 
 class CArrayProxy(ArrayProxy):
     # C array memory layout
+    _default_order = 'C'
+
+
+class DeprecatedCArrayProxy(ArrayProxy):
     order = 'C'
 
 
@@ -203,6 +210,38 @@ def test_order_override(order):
         assert_array_equal(arr[sliceobj], prox[sliceobj])
 
 
+def test_deprecated_order_classvar():
+    shape = (15, 16, 17)
+    arr = np.arange(np.prod(shape)).reshape(shape)
+    fobj = BytesIO()
+    fobj.write(arr.tobytes(order='C'))
+    sliceobj = (None, slice(None), 1, -1)
+
+    # We don't really care about the original order, just that the behavior
+    # of the deprecated mode matches the new behavior
+    fprox = ArrayProxy(fobj, (shape, arr.dtype), order='F')
+    cprox = ArrayProxy(fobj, (shape, arr.dtype), order='C')
+
+    # Start raising errors when we crank the dev version
+    if Version(__version__) >= Version('7.0.0.dev0'):
+        cm = pytest.raises(ExpiredDeprecationError)
+    else:
+        cm = pytest.deprecated_call()
+
+    with cm:
+        prox = DeprecatedCArrayProxy(fobj, (shape, arr.dtype))
+        assert prox.order == 'C'
+        assert_array_equal(prox[sliceobj], cprox[sliceobj])
+    with cm:
+        prox = DeprecatedCArrayProxy(fobj, (shape, arr.dtype), order='C')
+        assert prox.order == 'C'
+        assert_array_equal(prox[sliceobj], cprox[sliceobj])
+    with cm:
+        prox = DeprecatedCArrayProxy(fobj, (shape, arr.dtype), order='F')
+        assert prox.order == 'F'
+        assert_array_equal(prox[sliceobj], fprox[sliceobj])
+
+
 def test_is_proxy():
     # Test is_proxy function
     hdr = FunkyHeader((2, 3, 4))