From c104112d27922208d980ff8afe6e5132731823c9 Mon Sep 17 00:00:00 2001
From: Marten van Kerkwijk <mhvk@astro.utoronto.ca>
Date: Sat, 20 Feb 2016 20:03:40 -0500
Subject: [PATCH] Revert part of #3907 which incorrectly propogated MaskedArray
 info.

---
 numpy/ma/core.py                   | 15 +++++++++------
 numpy/ma/tests/test_subclassing.py | 20 ++++++++++++++++++++
 2 files changed, 29 insertions(+), 6 deletions(-)

diff --git a/numpy/ma/core.py b/numpy/ma/core.py
index 3dfe0c4e359c..f3d30d15c441 100644
--- a/numpy/ma/core.py
+++ b/numpy/ma/core.py
@@ -911,7 +911,7 @@ def __call__(self, a, *args, **kwargs):
         # Transform to
         masked_result = result.view(get_masked_subclass(a))
         masked_result._mask = m
-        masked_result._update_from(result)
+        masked_result._update_from(a)
         return masked_result
 
     def __str__(self):
@@ -999,7 +999,10 @@ def __call__(self, a, b, *args, **kwargs):
         # Transforms to a (subclass of) MaskedArray
         masked_result = result.view(get_masked_subclass(a, b))
         masked_result._mask = m
-        masked_result._update_from(result)
+        if isinstance(a, MaskedArray):
+            masked_result._update_from(a)
+        elif isinstance(b, MaskedArray):
+            masked_result._update_from(b)
         return masked_result
 
     def reduce(self, target, axis=0, dtype=None):
@@ -1030,7 +1033,6 @@ def reduce(self, target, axis=0, dtype=None):
                 return tr
         masked_tr = tr.view(tclass)
         masked_tr._mask = mr
-        masked_tr._update_from(tr)
         return masked_tr
 
     def outer(self, a, b):
@@ -1056,7 +1058,6 @@ def outer(self, a, b):
             return d
         masked_d = d.view(get_masked_subclass(a, b))
         masked_d._mask = m
-        masked_d._update_from(d)
         return masked_d
 
     def accumulate(self, target, axis=0):
@@ -1068,7 +1069,6 @@ def accumulate(self, target, axis=0):
         t = filled(target, self.filly)
         result = self.f.accumulate(t, axis)
         masked_result = result.view(tclass)
-        masked_result._update_from(result)
         return masked_result
 
     def __str__(self):
@@ -1145,7 +1145,10 @@ def __call__(self, a, b, *args, **kwargs):
         # Transforms to a (subclass of) MaskedArray
         masked_result = result.view(get_masked_subclass(a, b))
         masked_result._mask = m
-        masked_result._update_from(result)
+        if isinstance(a, MaskedArray):
+            masked_result._update_from(a)
+        elif isinstance(b, MaskedArray):
+            masked_result._update_from(b)
         return masked_result
 
     def __str__(self):
diff --git a/numpy/ma/tests/test_subclassing.py b/numpy/ma/tests/test_subclassing.py
index 68734425c715..814ed5977fed 100644
--- a/numpy/ma/tests/test_subclassing.py
+++ b/numpy/ma/tests/test_subclassing.py
@@ -47,6 +47,14 @@ def __iadd__(self, other):
 subarray = SubArray
 
 
+class SubMaskedArray(MaskedArray):
+    """Pure subclass of MaskedArray, keeping some info on subclass."""
+    def __new__(cls, info=None, **kwargs):
+        obj = super(SubMaskedArray, cls).__new__(cls, **kwargs)
+        obj._optinfo['info'] = info
+        return obj
+
+
 class MSubArray(SubArray, MaskedArray):
 
     def __new__(cls, data, info={}, mask=nomask):
@@ -332,6 +340,18 @@ def test_subclass_str(self):
         mxcsub = masked_array(xcsub, mask=[True, False, True, False, False])
         self.assertTrue(str(mxcsub) == 'myprefix [-- 1 -- 3 4] mypostfix')
 
+    def test_pure_subclass_info_preservation(self):
+        # Test that ufuncs and methods conserve extra information consistently;
+        # see gh-7122.
+        arr1 = SubMaskedArray('test', data=[1,2,3,4,5,6])
+        arr2 = SubMaskedArray(data=[0,1,2,3,4,5])
+        diff1 = np.subtract(arr1, arr2)
+        self.assertTrue('info' in diff1._optinfo)
+        self.assertTrue(diff1._optinfo['info'] == 'test')
+        diff2 = arr1 - arr2
+        self.assertTrue('info' in diff2._optinfo)
+        self.assertTrue(diff2._optinfo['info'] == 'test')
+
 
 ###############################################################################
 if __name__ == '__main__':