BUG: Ensure that fully masked arrays pass assert_array_equal.

The underlying problem is that ma.all() evaluates to masked,
which is falsy, and thus triggers test failures.

2 files changed, 23 insertions, 1 deletions

diff --git a/numpy/testing/_private/utils.py b/numpy/testing/_private/utils.py
index b0c0b0c48..c420e1fb5 100644
--- a/numpy/testing/_private/utils.py
+++ b/numpy/testing/_private/utils.py
@@ -771,7 +771,11 @@ def assert_array_compare(comparison, x, y, err_msg='', verbose=True,
             reduced = val.ravel()
             cond = reduced.all()
             reduced = reduced.tolist()
-        if not cond:
+        # The below comparison is a hack to ensure that fully masked
+        # results, for which val.ravel().all() returns np.ma.masked,
+        # do not trigger a failure (np.ma.masked != True evaluates as
+        # np.ma.masked, which is falsy).
+        if cond != True:
             match = 100-100.0*reduced.count(1)/len(reduced)
             msg = build_err_msg([x, y],
                                 err_msg
diff --git a/numpy/testing/tests/test_utils.py b/numpy/testing/tests/test_utils.py
index c9e8384c2..602cdf5f2 100644
--- a/numpy/testing/tests/test_utils.py
+++ b/numpy/testing/tests/test_utils.py
@@ -366,6 +366,24 @@ class TestArrayAlmostEqual(_GenericTest):
         self._assert_func(b, a)
         self._assert_func(b, b)
 
+        # Test fully masked as well (see gh-11123).
+        a = np.ma.MaskedArray(3.5, mask=True)
+        b = np.array([3., 4., 6.5])
+        self._test_equal(a, b)
+        self._test_equal(b, a)
+        a = np.ma.masked
+        b = np.array([3., 4., 6.5])
+        self._test_equal(a, b)
+        self._test_equal(b, a)
+        a = np.ma.MaskedArray([3., 4., 6.5], mask=[True, True, True])
+        b = np.array([1., 2., 3.])
+        self._test_equal(a, b)
+        self._test_equal(b, a)
+        a = np.ma.MaskedArray([3., 4., 6.5], mask=[True, True, True])
+        b = np.array(1.)
+        self._test_equal(a, b)
+        self._test_equal(b, a)
+
     def test_subclass_that_cannot_be_bool(self):
         # While we cannot guarantee testing functions will always work for
         # subclasses, the tests should ideally rely only on subclasses having