BUG: Allow empty strings to be viewed as themselves

2 files changed, 22 insertions, 15 deletions

diff --git a/numpy/core/src/multiarray/getset.c b/numpy/core/src/multiarray/getset.c
index 77d9b8c66..d58071239 100644
--- a/numpy/core/src/multiarray/getset.c
+++ b/numpy/core/src/multiarray/getset.c
@@ -469,22 +469,18 @@ array_descr_set(PyArrayObject *self, PyObject *arg)
         Py_DECREF(safe);
     }
 
-    if (newtype->elsize == 0) {
-        /* Allow a void view */
-        if (newtype->type_num == NPY_VOID) {
-            PyArray_DESCR_REPLACE(newtype);
-            if (newtype == NULL) {
-                return -1;
-            }
-            newtype->elsize = PyArray_DESCR(self)->elsize;
-        }
-        /* But no other flexible types */
-        else {
-            PyErr_SetString(PyExc_TypeError,
-                    "data-type must not be 0-sized");
-            Py_DECREF(newtype);
+    /*
+     * Treat V0 as resizable void - unless the destination is already V0, then
+     * don't allow np.void to be duplicated
+     */
+    if (newtype->type_num == NPY_VOID &&
+            newtype->elsize == 0 &&
+            PyArray_DESCR(self)->elsize != 0) {
+        PyArray_DESCR_REPLACE(newtype);
+        if (newtype == NULL) {
             return -1;
         }
+        newtype->elsize = PyArray_DESCR(self)->elsize;
     }
 
 
@@ -532,7 +528,8 @@ array_descr_set(PyArrayObject *self, PyObject *arg)
 
         if (newtype->elsize < PyArray_DESCR(self)->elsize) {
             /* if it is compatible, increase the size of the relevant axis */
-            if (PyArray_DESCR(self)->elsize % newtype->elsize != 0) {
+            if (newtype->elsize == 0 ||
+                    PyArray_DESCR(self)->elsize % newtype->elsize != 0) {
                 PyErr_SetString(PyExc_ValueError,
                         "When changing to a smaller dtype, its size must be a "
                         "divisor of the size of original dtype");
diff --git a/numpy/core/tests/test_multiarray.py b/numpy/core/tests/test_multiarray.py
index 8ab2c97f5..8bb91619e 100644
--- a/numpy/core/tests/test_multiarray.py
+++ b/numpy/core/tests/test_multiarray.py
@@ -1252,6 +1252,16 @@ class TestZeroSizeFlexible(object):
             zs.resize(25)
             zs.resize((10, 10))
 
+    def test_view(self):
+        for dt in [bytes, np.void, unicode]:
+            zs = self._zeros(10, dt)
+
+            # viewing as itself should be allowed
+            assert_equal(zs.view(dt).dtype, np.dtype(dt))
+
+            # viewing as any non-empty type gives an empty result
+            assert_equal(zs.view((dt, 1)).shape, (0,))
+
 
 class TestMethods(object):
     def test_compress(self):