BUG: Fix gh-8069

Fill values were not correctly calculated for subdtypes, instead returning `None`

2 files changed, 15 insertions, 1 deletions

diff --git a/numpy/ma/core.py b/numpy/ma/core.py
index e091baa22..d0b18fb3a 100644
--- a/numpy/ma/core.py
+++ b/numpy/ma/core.py
@@ -277,7 +277,12 @@ def _recursive_extremum_fill_value(ndtype, extremum):
             fval = _recursive_extremum_fill_value(ndtype[name], extremum)
             deflist.append(fval)
         return tuple(deflist)
-    return extremum[ndtype]
+    elif ndtype.subdtype:
+        subtype, shape = ndtype.subdtype
+        subval = _recursive_extremum_fill_value(subtype, extremum)
+        return np.full(shape, subval)
+    else:
+        return extremum[ndtype]
 
 
 def _extremum_fill_value(obj, extremum, extremum_name):
diff --git a/numpy/ma/tests/test_core.py b/numpy/ma/tests/test_core.py
index bba8f2cb7..26099455d 100644
--- a/numpy/ma/tests/test_core.py
+++ b/numpy/ma/tests/test_core.py
@@ -1879,6 +1879,15 @@ class TestFillingValues(TestCase):
         assert_equal(test[1][1], maximum_fill_value(a['B']['BB']))
         assert_equal(test[1], maximum_fill_value(a['B']))
 
+    def test_extremum_fill_value_subdtype(self):
+        a = array(([2, 3, 4],), dtype=[('value', np.int8, 3)])
+
+        test = minimum_fill_value(a)
+        assert_equal(test[0], np.full(3, minimum_fill_value(a['value'])))
+
+        test = maximum_fill_value(a)
+        assert_equal(test[0], np.full(3, maximum_fill_value(a['value'])))
+
     def test_fillvalue_individual_fields(self):
         # Test setting fill_value on individual fields
         ndtype = [('a', int), ('b', int)]