Reject arrays in deeply nested asarray inputs

array_api_strict/_creation_functions.py

@@ -48,6 +48,16 @@ def _supports_buffer_protocol(obj: object) -> TypeIs[SupportsBufferProtocol]:
     return True
 
 
+def _contains_nested_array(obj: list[object] | tuple[object, ...]) -> bool:
+    from ._array_object import Array
+
+    return any(
+        isinstance(item, Array)
+        or isinstance(item, list | tuple) and _contains_nested_array(item)
+        for item in obj
+    )
+
+
 def asarray(
     obj: Array | complex | NestedSequence[complex] | SupportsBufferProtocol,
     /,
@@ -97,7 +107,7 @@ def asarray(
 
     if isinstance(obj, Array):
         return Array._new(np.array(obj._array, copy=copy, dtype=_np_dtype), device=device)
-    elif isinstance(obj, list | tuple) and any(isinstance(x, Array) for x in obj):
+    elif isinstance(obj, list | tuple) and _contains_nested_array(obj):
         raise TypeError("Nested Arrays are not allowed. Use `stack` instead.")
 
     if dtype is None and isinstance(obj, int) and (obj > 2 ** 64 or obj < -(2 ** 63)):

array_api_strict/tests/test_creation_functions.py

@@ -116,6 +116,33 @@ def test_asarray_nested_arrays():
         asarray([1, asarray(1)])
 
 
+@pytest.mark.parametrize("outer", [list, tuple])
+@pytest.mark.parametrize("inner", [list, tuple])
+@pytest.mark.parametrize("array_value", [1, [1]])
+@pytest.mark.parametrize("depth", [2, 3])
+def test_asarray_deeply_nested_arrays(outer, inner, array_value, depth):
+    obj = asarray(array_value)
+    for _ in range(depth - 1):
+        obj = inner([obj])
+    obj = outer([obj])
+    with pytest.raises(TypeError, match="Nested Arrays are not allowed"):
+        asarray(obj)
+
+
+def test_asarray_nested_array_after_scalars():
+    with pytest.raises(TypeError, match="Nested Arrays are not allowed"):
+        asarray([[1, 2], [3, asarray(4)]])
+
+
+@pytest.mark.parametrize("outer", [list, tuple])
+@pytest.mark.parametrize("inner", [list, tuple])
+def test_asarray_nested_scalars(outer, inner):
+    obj = outer([inner([1, 2]), inner([3, 4])])
+    res = asarray(obj)
+    assert res.shape == (2, 2)
+    assert all(res == asarray([[1, 2], [3, 4]]))
+
+
 def test_asarray_device_inference():
     assert asarray([1, 2, 3]).device == CPU_DEVICE