BUG: Allow __array_interface__['shape'] == () (#7994)

Previously this would fail when __array_interface__['data'] is a buffer object.

gh-2897 already removed this check for other types of data.

2 files changed, 27 insertions, 6 deletions

diff --git a/numpy/core/src/multiarray/ctors.c b/numpy/core/src/multiarray/ctors.c
index 7958c619f..701f1da73 100644
--- a/numpy/core/src/multiarray/ctors.c
+++ b/numpy/core/src/multiarray/ctors.c
@@ -2301,12 +2301,7 @@ PyArray_FromInterface(PyObject *origin)
 
     /* Case for data access through buffer */
     else if (attr) {
-        if (n == 0) {
-            PyErr_SetString(PyExc_ValueError,
-                    "__array_interface__ shape must be at least size 1");
-            goto fail;
-        }
-        if (attr && (attr != Py_None)) {
+        if (attr != Py_None) {
             base = attr;
         }
         else {
diff --git a/numpy/core/tests/test_multiarray.py b/numpy/core/tests/test_multiarray.py
index b1a6fbe44..4808303ae 100644
--- a/numpy/core/tests/test_multiarray.py
+++ b/numpy/core/tests/test_multiarray.py
@@ -6529,6 +6529,32 @@ def test_array_interface_itemsize():
     assert_equal(descr_t.itemsize, typestr_t.itemsize)
 
 
+def test_array_interface_empty_shape():
+    # See gh-7994
+    arr = np.array([1, 2, 3])
+    interface1 = dict(arr.__array_interface__)
+    interface1['shape'] = ()
+
+    class DummyArray1(object):
+        __array_interface__ = interface1
+
+    # NOTE: Because Py2 str/Py3 bytes supports the buffer interface, setting
+    # the interface data to bytes would invoke the bug this tests for, that
+    # __array_interface__ with shape=() is not allowed if the data is an object
+    # exposing the buffer interface
+    interface2 = dict(interface1)
+    interface2['data'] = arr[0].tobytes()
+
+    class DummyArray2(object):
+        __array_interface__ = interface2
+
+    arr1 = np.asarray(DummyArray1())
+    arr2 = np.asarray(DummyArray2())
+    arr3 = arr[:1].reshape(())
+    assert_equal(arr1, arr2)
+    assert_equal(arr1, arr3)
+
+
 def test_flat_element_deletion():
     it = np.ones(3).flat
     try: