Merge pull request #15881 from eric-wieser/empty_like-0d

BUG: Fix empty_like to respect shape=()

3 files changed, 8 insertions, 7 deletions

diff --git a/numpy/core/src/multiarray/ctors.c b/numpy/core/src/multiarray/ctors.c
index a23510c8b..12bf9eace 100644
--- a/numpy/core/src/multiarray/ctors.c
+++ b/numpy/core/src/multiarray/ctors.c
@@ -1211,8 +1211,8 @@ PyArray_NewFromDescrAndBase(
  *             NPY_ANYORDER - Fortran if prototype is Fortran, C otherwise.
  *             NPY_KEEPORDER - Keeps the axis ordering of prototype.
  * dtype     - If not NULL, overrides the data type of the result.
- * ndim      - If not 0 and dims not NULL, overrides the shape of the result.
- * dims      - If not NULL and ndim not 0, overrides the shape of the result.
+ * ndim      - If not -1, overrides the shape of the result.
+ * dims      - If ndim is not -1, overrides the shape of the result.
  * subok     - If 1, use the prototype's array subtype, otherwise
  *             always create a base-class array.
  *
@@ -1225,7 +1225,7 @@ PyArray_NewLikeArrayWithShape(PyArrayObject *prototype, NPY_ORDER order,
 {
     PyObject *ret = NULL;
 
-    if (dims == NULL) {
+    if (ndim == -1) {
         ndim = PyArray_NDIM(prototype);
         dims = PyArray_DIMS(prototype);
     }
@@ -1322,7 +1322,7 @@ NPY_NO_EXPORT PyObject *
 PyArray_NewLikeArray(PyArrayObject *prototype, NPY_ORDER order,
                      PyArray_Descr *dtype, int subok)
 {
-    return PyArray_NewLikeArrayWithShape(prototype, order, dtype, 0, NULL, subok);
+    return PyArray_NewLikeArrayWithShape(prototype, order, dtype, -1, NULL, subok);
 }
 
 /*NUMPY_API
diff --git a/numpy/core/src/multiarray/multiarraymodule.c b/numpy/core/src/multiarray/multiarraymodule.c
index 2856a123f..9e8022abd 100644
--- a/numpy/core/src/multiarray/multiarraymodule.c
+++ b/numpy/core/src/multiarray/multiarraymodule.c
@@ -1857,14 +1857,15 @@ array_empty_like(PyObject *NPY_UNUSED(ignored), PyObject *args, PyObject *kwds)
     NPY_ORDER order = NPY_KEEPORDER;
     PyArrayObject *ret = NULL;
     int subok = 1;
-    PyArray_Dims shape = {NULL, 0};
+    /* -1 is a special value meaning "not specified" */
+    PyArray_Dims shape = {NULL, -1};
 
     if (!PyArg_ParseTupleAndKeywords(args, kwds, "O&|O&O&iO&:empty_like", kwlist,
                 &PyArray_Converter, &prototype,
                 &PyArray_DescrConverter2, &dtype,
                 &PyArray_OrderConverter, &order,
                 &subok,
-                &PyArray_IntpConverter, &shape)) {
+                &PyArray_OptionalIntpConverter, &shape)) {
         goto fail;
     }
     /* steals the reference to dtype if it's not NULL */
diff --git a/numpy/core/tests/test_numeric.py b/numpy/core/tests/test_numeric.py
index 05f59d9dc..dfb2d81fe 100644
--- a/numpy/core/tests/test_numeric.py
+++ b/numpy/core/tests/test_numeric.py
@@ -2457,7 +2457,7 @@ class TestLikeFuncs:
                 (np.arange(24).reshape(2, 3, 4).swapaxes(0, 1), None),
                 (np.arange(24).reshape(4, 3, 2).swapaxes(0, 1), '?'),
                      ]
-        self.shapes = [(5,), (5,6,), (5,6,7,)]
+        self.shapes = [(), (5,), (5,6,), (5,6,7,)]
 
     def compare_array_value(self, dz, value, fill_value):
         if value is not None: