Fix dpnp.insert ignoring out-of-bounds negative indices in multi-element obj

CHANGELOG.md

@@ -90,6 +90,7 @@ This release is compatible with NumPy 2.5.
 * Fixed `dpnp.all` and `dpnp.any` aborting when reducing over an empty axis (e.g. an array with a zero-length dimension) [#3021](https://github.com/IntelPython/dpnp/pull/3021)
 * Released the GIL before the blocking OneMKL DFT calls in the FFT extension [#3040](https://github.com/IntelPython/dpnp/pull/3040)
 * Fixed `astype` casting an out-of-range floating point value to a signed narrow integer type saturating to the destination min/max instead of wrapping like NumPy, generalizing the earlier unsigned-only fix [#3033](https://github.com/IntelPython/dpnp/pull/3033)
+* Fixed `dpnp.insert` silently ignoring out-of-bounds negative indices in a multi-element `obj`, so a mix of in-bounds and out-of-bounds indices now consistently raises `IndexError` [#3041](https://github.com/IntelPython/dpnp/pull/3041)
 
 ### Security
 

dpnp/dpnp_iface_manipulation.py

@@ -240,6 +240,35 @@ def _calc_parameters(a, axis, obj, values=None):
     )
 
 
+def _check_index_bounds(obj, indices, n, axis):
+    """
+    Raise ``IndexError`` if any index in `obj` is out of bounds for `axis`.
+
+    Mirrors the size-1 path in ``_insert_singleton_index``: when `obj` lives on
+    the host (a Python sequence/scalar or NumPy array) the bounds are validated
+    with NumPy, avoiding a device sync entirely. A slice cannot be out of bounds
+    (``obj.indices(n)`` is clamped to ``[0, n]``), so it is skipped. Only a
+    device array `obj` needs a single host transfer to read its extremes.
+
+    """
+
+    if isinstance(obj, slice) or indices.size == 0:
+        return
+
+    if dpnp.is_supported_array_type(obj):
+        min_idx, max_idx = dpnp.stack([indices.min(), indices.max()]).asnumpy()
+    else:
+        host_obj = numpy.asarray(obj)
+        min_idx, max_idx = host_obj.min(), host_obj.max()
+
+    min_idx, max_idx = int(min_idx), int(max_idx)
+    if min_idx < -n or max_idx > n:
+        oob = min_idx if min_idx < -n else max_idx
+        raise IndexError(
+            f"index {oob} is out of bounds for axis {axis} with size {n}"
+        )
+
+
 def _insert_array_indices(parameters, indices, values, obj):
     """
     Utility function for ``dpnp.insert`` when indices is an array with
@@ -2435,6 +2464,13 @@ def insert(arr, obj, values, axis=None):
         does not occur in-place: a new array is returned. If
         `axis` is ``None``, `out` is a flattened array.
 
+    Warnings
+    --------
+    This function might synchronize in order to validate that the indices are
+    within bounds. This may harm performance in some applications. To avoid
+    synchronization, pass `obj` as a Python scalar or sequence, or as a NumPy
+    array.
+
     See Also
     --------
     :obj:`dpnp.append` : Append elements at the end of an array.
@@ -2522,8 +2558,10 @@ def insert(arr, obj, values, axis=None):
             )
 
     if indices.size == 1:
+        # the size-1 path validates the bounds itself while reading the index
         return _insert_singleton_index(params, indices, values, obj)
 
+    _check_index_bounds(obj, indices, params.n, params.axis)
     return _insert_array_indices(params, indices, values, obj)
 
 

dpnp/tests/test_manipulation.py

@@ -815,11 +815,32 @@ def test_error(self):
         with pytest.raises(TypeError):
             dpnp.insert(a, [], 2, axis="nonsense")
 
-    @pytest.mark.parametrize("idx", [4, -4])
-    def test_index_out_of_bounds(self, idx):
-        a = dpnp.array([0, 1, 2])
+    @testing.with_requires("numpy>=2.6")
+    @pytest.mark.parametrize("xp", [numpy, dpnp])
+    @pytest.mark.parametrize(
+        "idx, values",
+        [
+            # single-element obj -> singleton path
+            ([4], [3, 4]),
+            ([-4], [3, 4]),
+            # multi-element obj -> array path
+            ([-6, 0], [9, 8]),
+            ([0, 6], [9, 8]),
+            ([4, 4], [3, 4]),
+            ([-4, -5], [3, 4]),
+        ],
+    )
+    def test_index_out_of_bounds(self, xp, idx, values):
+        a = xp.array([0, 1, 2])
+        with pytest.raises(IndexError, match="out of bounds"):
+            xp.insert(a, idx, values)
+
+    @pytest.mark.parametrize("xp", [numpy, dpnp])
+    @pytest.mark.parametrize("axis", [0, 1])
+    def test_index_out_of_bounds_ndim(self, xp, axis):
+        a = xp.ones((3, 3))
         with pytest.raises(IndexError, match="out of bounds"):
-            dpnp.insert(a, [idx], [3, 4])
+            xp.insert(a, [5, 0], 9, axis=axis)
 
 
 # array_split has more comprehensive test of splitting.