BUG: Remove incorrect flags propagation in boolean indexing

seberg · seberg · commit cee5f8657c08 · 2024-11-21T16:51:33.000+01:00
Flags don't need to be propagated from the original array. Progating from the result array makes sense and is safe, but really... the only flag we normally need is writeable. (However, this is a typical pattern right now.) Expands the test to cover these cases. Closes gh-27777
diff --git a/numpy/_core/src/multiarray/mapping.c b/numpy/_core/src/multiarray/mapping.c
@@ -1058,7 +1058,7 @@ array_boolean_subscript(PyArrayObject *self,
         ret = (PyArrayObject *)PyArray_NewFromDescrAndBase(
                 Py_TYPE(self), ret_dtype,
                 1, &size, PyArray_STRIDES(ret), PyArray_BYTES(ret),
-                PyArray_FLAGS(self), (PyObject *)self, (PyObject *)tmp);
+                PyArray_FLAGS(ret), (PyObject *)self, (PyObject *)tmp);
 
         Py_DECREF(tmp);
         if (ret == NULL) {
diff --git a/numpy/_core/tests/test_indexing.py b/numpy/_core/tests/test_indexing.py
@@ -409,15 +409,19 @@ def test_array_like_values(self):
         a[...] = memoryview(s)
         assert_array_equal(a, s)
 
-    def test_subclass_writeable(self):
+    @pytest.mark.parametrize("writeable", [True, False])
+    def test_subclass_writeable(self, writeable):
         d = np.rec.array([('NGC1001', 11), ('NGC1002', 1.), ('NGC1003', 1.)],
                          dtype=[('target', 'S20'), ('V_mag', '>f4')])
+        d.flags.writeable = writeable
+        # Advanced indexing results are always writeable:
         ind = np.array([False,  True,  True], dtype=bool)
-        assert_(d[ind].flags.writeable)
+        assert d[ind].flags.writeable
         ind = np.array([0, 1])
-        assert_(d[ind].flags.writeable)
-        assert_(d[...].flags.writeable)
-        assert_(d[0].flags.writeable)
+        assert d[ind].flags.writeable
+        # Views should be writeable if the original array is:
+        assert d[...].flags.writeable == writeable
+        assert d[0].flags.writeable == writeable
 
     def test_memory_order(self):
         # This is not necessary to preserve. Memory layouts for
