Merge pull request numpy#10314 from mhvk/ma-array-finalize-mask-view

eric-wieser · web-flow · commit 6ccb03d5e0bf · 2018-05-29T00:54:27.000-07:00
BUG: Ensure __array_finalize__ cannot back-mangle shape
diff --git a/numpy/ma/core.py b/numpy/ma/core.py
@@ -2992,7 +2992,9 @@ def __array_finalize__(self, obj):
                     order = "K"
 
                 _mask = _mask.astype(_mask_dtype, order)
-
+            else:
+                # Take a view so shape changes, etc., do not propagate back.
+                _mask = _mask.view()
         else:
             _mask = nomask
 
@@ -3337,17 +3339,35 @@ def __setitem__(self, indx, value):
             _mask[indx] = mindx
         return
 
-    def __setattr__(self, attr, value):
-        super(MaskedArray, self).__setattr__(attr, value)
-        if attr == 'dtype' and self._mask is not nomask:
-            self._mask = self._mask.view(make_mask_descr(value), ndarray)
-            # Try to reset the shape of the mask (if we don't have a void)
-            # This raises a ValueError if the dtype change won't work
+    # Define so that we can overwrite the setter.
+    @property
+    def dtype(self):
+        return super(MaskedArray, self).dtype
+
+    @dtype.setter
+    def dtype(self, dtype):
+        super(MaskedArray, type(self)).dtype.__set__(self, dtype)
+        if self._mask is not nomask:
+            self._mask = self._mask.view(make_mask_descr(dtype), ndarray)
+            # Try to reset the shape of the mask (if we don't have a void).
+            # This raises a ValueError if the dtype change won't work.
             try:
                 self._mask.shape = self.shape
             except (AttributeError, TypeError):
                 pass
 
+    @property
+    def shape(self):
+        return super(MaskedArray, self).shape
+
+    @shape.setter
+    def shape(self, shape):
+        super(MaskedArray, type(self)).shape.__set__(self, shape)
+        # Cannot use self._mask, since it may not (yet) exist when a
+        # masked matrix sets the shape.
+        if getmask(self) is not nomask:
+            self._mask.shape = self.shape
+
     def __setmask__(self, mask, copy=False):
         """
         Set the mask.
diff --git a/numpy/ma/tests/test_core.py b/numpy/ma/tests/test_core.py
@@ -352,9 +352,11 @@ def test_copy(self):
         assert_equal(y1._mask.__array_interface__, m.__array_interface__)
 
         y1a = array(y1)
+        # Default for masked array is not to copy; see gh-10318.
         assert_(y1a._data.__array_interface__ ==
                         y1._data.__array_interface__)
-        assert_(y1a.mask is y1.mask)
+        assert_(y1a._mask.__array_interface__ ==
+                        y1._mask.__array_interface__)
 
         y2 = array(x1, mask=m3)
         assert_(y2._data.__array_interface__ == x1.__array_interface__)
diff --git a/numpy/ma/tests/test_old_ma.py b/numpy/ma/tests/test_old_ma.py
@@ -273,7 +273,11 @@ def test_testCopySize(self):
         assert_(y1.mask is m)
 
         y1a = array(y1, copy=0)
-        assert_(y1a.mask is y1.mask)
+        # For copy=False, one might expect that the array would just
+        # passed on, i.e., that it would be "is" instead of "==".
+        # See gh-4043 for discussion.
+        assert_(y1a._mask.__array_interface__ ==
+                y1._mask.__array_interface__)
 
         y2 = array(x1, mask=m3, copy=0)
         assert_(y2.mask is m3)
diff --git a/numpy/ma/tests/test_regression.py b/numpy/ma/tests/test_regression.py
@@ -74,3 +74,13 @@ def test_ddof_corrcoef(self):
             r1 = np.ma.corrcoef(x, y, ddof=1)
             # ddof should not have an effect (it gets cancelled out)
             assert_allclose(r0.data, r1.data)
+
+    def test_mask_not_backmangled(self):
+        # See gh-10314.  Test case taken from gh-3140.
+        a = np.ma.MaskedArray([1., 2.], mask=[False, False])
+        assert_(a.mask.shape == (2,))
+        b = np.tile(a, (2, 1))
+        # Check that the above no longer changes a.shape to (1, 2)
+        assert_(a.mask.shape == (2,))
+        assert_(b.shape == (2, 2))
+        assert_(b.mask.shape == (2, 2))
