Merge pull request numpy#26268 from mtsokol/nonzero-0d-input

API: Disallow 0D input arrays in ``nonzero``

Author: ngoldbaum

doc/release/upcoming_changes/26268.expired.rst

@@ -0,0 +1 @@
+* Scalars and 0D arrays are disallowed for `numpy.nonzero` and `numpy.ndarray.nonzero`.

numpy/_core/src/multiarray/item_selection.c

@@ -2797,6 +2797,23 @@ NPY_NO_EXPORT PyObject *
 PyArray_Nonzero(PyArrayObject *self)
 {
     int i, ndim = PyArray_NDIM(self);
+    if (ndim == 0) {
+        char const* msg;
+        if (PyArray_ISBOOL(self)) {
+            msg =
+                "Calling nonzero on 0d arrays is not allowed. "
+                "Use np.atleast_1d(scalar).nonzero() instead. "
+                "If the context of this error is of the form "
+                "`arr[nonzero(cond)]`, just use `arr[cond]`.";
+        } else {
+            msg =
+                "Calling nonzero on 0d arrays is not allowed. "
+                "Use np.atleast_1d(scalar).nonzero() instead.";
+        }
+        PyErr_SetString(PyExc_ValueError, msg);
+        return NULL;
+    }
+
     PyArrayObject *ret = NULL;
     PyObject *ret_tuple;
     npy_intp ret_dims[2];
@@ -2818,42 +2835,6 @@ PyArray_Nonzero(PyArrayObject *self)
     nonzero = PyDataType_GetArrFuncs(dtype)->nonzero;
     needs_api = PyDataType_FLAGCHK(dtype, NPY_NEEDS_PYAPI);
 
-    /* Special case - nonzero(zero_d) is nonzero(atleast_1d(zero_d)) */
-    if (ndim == 0) {
-        char const* msg;
-        if (PyArray_ISBOOL(self)) {
-            msg =
-                "Calling nonzero on 0d arrays is deprecated, as it behaves "
-                "surprisingly. Use `atleast_1d(cond).nonzero()` if the old "
-                "behavior was intended. If the context of this warning is of "
-                "the form `arr[nonzero(cond)]`, just use `arr[cond]`.";
-        }
-        else {
-            msg =
-                "Calling nonzero on 0d arrays is deprecated, as it behaves "
-                "surprisingly. Use `atleast_1d(arr).nonzero()` if the old "
-                "behavior was intended.";
-        }
-        if (DEPRECATE(msg) < 0) {
-            return NULL;
-        }
-
-        static npy_intp const zero_dim_shape[1] = {1};
-        static npy_intp const zero_dim_strides[1] = {0};
-
-        Py_INCREF(PyArray_DESCR(self));  /* array creation steals reference */
-        PyArrayObject *self_1d = (PyArrayObject *)PyArray_NewFromDescrAndBase(
-            Py_TYPE(self), PyArray_DESCR(self),
-            1, zero_dim_shape, zero_dim_strides, PyArray_BYTES(self),
-            PyArray_FLAGS(self), (PyObject *)self, (PyObject *)self);
-        if (self_1d == NULL) {
-            return NULL;
-        }
-        ret_tuple = PyArray_Nonzero(self_1d);
-        Py_DECREF(self_1d);
-        return ret_tuple;
-    }
-
     /*
      * First count the number of non-zeros in 'self'.
      */

numpy/_core/tests/test_deprecations.py

@@ -283,13 +283,6 @@ def test_deprecate_unparsable_string(self, invalid_str):
             assert_array_equal(res, x)
 
 
-class TestNonZero(_DeprecationTestCase):
-    # 2019-05-26, 1.17.0
-    def test_zerod(self):
-        self.assert_deprecated(lambda: np.nonzero(np.array(0)))
-        self.assert_deprecated(lambda: np.nonzero(np.array(1)))
-
-
 class TestToString(_DeprecationTestCase):
     # 2020-03-06 1.19.0
     message = re.escape("tostring() is deprecated. Use tobytes() instead.")

numpy/_core/tests/test_numeric.py

@@ -1567,16 +1567,12 @@ def test_nonzero_trivial(self):
         assert_equal(np.count_nonzero(np.array([1], dtype='?')), 1)
         assert_equal(np.nonzero(np.array([1])), ([0],))
 
-    def test_nonzero_zerod(self):
-        assert_equal(np.count_nonzero(np.array(0)), 0)
-        assert_equal(np.count_nonzero(np.array(0, dtype='?')), 0)
-        with assert_warns(DeprecationWarning):
-            assert_equal(np.nonzero(np.array(0)), ([],))
-
-        assert_equal(np.count_nonzero(np.array(1)), 1)
-        assert_equal(np.count_nonzero(np.array(1, dtype='?')), 1)
-        with assert_warns(DeprecationWarning):
-            assert_equal(np.nonzero(np.array(1)), ([0],))
+    def test_nonzero_zerodim(self):
+        err_msg = "Calling nonzero on 0d arrays is not allowed"
+        with assert_raises_regex(ValueError, err_msg):
+            np.nonzero(np.array(0))
+        with assert_raises_regex(ValueError, err_msg):
+            np.array(1).nonzero()
 
     def test_nonzero_onedim(self):
         x = np.array([1, 0, 2, -1, 0, 0, 8])

tools/ci/array-api-skips.txt

@@ -14,9 +14,6 @@ array_api_tests/test_signatures.py::test_func_signature[reshape]
 array_api_tests/test_signatures.py::test_func_signature[argsort]
 array_api_tests/test_signatures.py::test_func_signature[sort]
 
-# nonzero for 0D should error
-array_api_tests/test_searching_functions.py::test_nonzero_zerodim_error
-
 # TODO: check why in CI `inspect.signature(np.vecdot)` returns (*arg, **kwarg)
 #       instead of raising ValueError. mtsokol: couldn't reproduce locally
 array_api_tests/test_signatures.py::test_func_signature[vecdot]