BUG: Fix array_split empty array type and add FutureWarning

Fixes the result type of empty output arrays.

The FutureWarning warns about changed behaviour. A "kludge" was
introduced into array split converting converting the result of
something like:

>>> np.array_split(np.array([[1, 1]]), 2)
[array([[1, 1]]), array([], dtype=int64)]

instead of retaining the shape of the empty/second array to
be (0, 2). A FutureWarning is now raised when such a
replacement occurs.

Closes gh-612

1 files changed, 8 insertions, 2 deletions

diff --git a/numpy/lib/tests/test_shape_base.py b/numpy/lib/tests/test_shape_base.py
index 55b008871..d6d01ba99 100644
--- a/numpy/lib/tests/test_shape_base.py
+++ b/numpy/lib/tests/test_shape_base.py
@@ -100,9 +100,12 @@ class TestArraySplit(TestCase):
 
     def test_integer_split_2D_rows(self):
         a = array([arange(10), arange(10)])
-        res = array_split(a, 3, axis=0)
+        res = assert_warns(FutureWarning, array_split, a, 3, axis=0)
+
+        # After removing the FutureWarning, the last should be zeros((0, 10))
         desired = [array([arange(10)]), array([arange(10)]), array([])]
         compare_results(res, desired)
+        assert_(a.dtype.type is res[-1].dtype.type)
 
     def test_integer_split_2D_cols(self):
         a = array([arange(10), arange(10)])
@@ -116,9 +119,12 @@ class TestArraySplit(TestCase):
         """ This will fail if we change default axis
         """
         a = array([arange(10), arange(10)])
-        res = array_split(a, 3)
+        res = assert_warns(FutureWarning, array_split, a, 3)
+
+        # After removing the FutureWarning, the last should be zeros((0, 10))
         desired = [array([arange(10)]), array([arange(10)]), array([])]
         compare_results(res, desired)
+        assert_(a.dtype.type is res[-1].dtype.type)
     #perhaps should check higher dimensions
 
     def test_index_split_simple(self):