Merge remote-tracking branch 'upstream/master' into fix-if-fields

1 files changed, 41 insertions, 2 deletions

diff --git a/numpy/lib/tests/test_stride_tricks.py b/numpy/lib/tests/test_stride_tricks.py
index b2bd7da3e..85fcceedc 100644
--- a/numpy/lib/tests/test_stride_tricks.py
+++ b/numpy/lib/tests/test_stride_tricks.py
@@ -4,7 +4,7 @@ import numpy as np
 from numpy.core._rational_tests import rational
 from numpy.testing import (
     assert_equal, assert_array_equal, assert_raises, assert_,
-    assert_raises_regex
+    assert_raises_regex, assert_warns,
     )
 from numpy.lib.stride_tricks import (
     as_strided, broadcast_arrays, _broadcast_shape, broadcast_to
@@ -415,12 +415,32 @@ def test_writeable():
     assert_equal(result.flags.writeable, False)
     assert_raises(ValueError, result.__setitem__, slice(None), 0)
 
-    # but the result of broadcast_arrays needs to be writeable (for now), to
+    # but the result of broadcast_arrays needs to be writeable, to
     # preserve backwards compatibility
+    for is_broadcast, results in [(False, broadcast_arrays(original,)),
+                                  (True, broadcast_arrays(0, original))]:
+        for result in results:
+            # This will change to False in a future version
+            if is_broadcast:
+                with assert_warns(FutureWarning):
+                    assert_equal(result.flags.writeable, True)
+                with assert_warns(DeprecationWarning):
+                    result[:] = 0
+                # Warning not emitted, writing to the array resets it
+                assert_equal(result.flags.writeable, True)
+            else:
+                # No warning:
+                assert_equal(result.flags.writeable, True)
+
     for results in [broadcast_arrays(original),
                     broadcast_arrays(0, original)]:
         for result in results:
+            # resets the warn_on_write DeprecationWarning
+            result.flags.writeable = True
+            # check: no warning emitted
             assert_equal(result.flags.writeable, True)
+            result[:] = 0
+            
     # keep readonly input readonly
     original.flags.writeable = False
     _, result = broadcast_arrays(0, original)
@@ -435,6 +455,25 @@ def test_writeable():
     assert_(first.shape == second.shape)
 
 
+def test_writeable_memoryview():
+    # The result of broadcast_arrays exports as a non-writeable memoryview
+    # because otherwise there is no good way to opt in to the new behaviour
+    # (i.e. you would need to set writeable to False explicitly).
+    # See gh-13929.
+    original = np.array([1, 2, 3])
+
+    for is_broadcast, results in [(False, broadcast_arrays(original,)),
+                                  (True, broadcast_arrays(0, original))]:
+        for result in results:
+            # This will change to False in a future version
+            if is_broadcast:
+                # memoryview(result, writable=True) will give warning but cannot
+                # be tested using the python API.
+                assert memoryview(result).readonly
+            else:
+                assert not memoryview(result).readonly
+
+
 def test_reference_types():
     input_array = np.array('a', dtype=object)
     expected = np.array(['a'] * 3, dtype=object)