Add warning wrappers that allow to call warnings from pybind level

CMakeLists.txt

@@ -180,7 +180,8 @@ set(PYBIND11_HEADERS
     include/pybind11/stl_bind.h
     include/pybind11/stl/filesystem.h
     include/pybind11/type_caster_pyobject_ptr.h
-    include/pybind11/typing.h)
+    include/pybind11/typing.h
+    include/pybind11/warnings.h)
 
 # Compare with grep and warn if mismatched
 if(PYBIND11_MASTER_PROJECT AND NOT CMAKE_VERSION VERSION_LESS 3.12)

include/pybind11/warnings.h

@@ -0,0 +1,70 @@
+/*
+    pybind11/warnings.h: Python warnings wrappers.
+
+    Copyright (c) 2024 Jan Iwaszkiewicz <[email protected]>
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+*/
+
+#pragma once
+
+#include "pybind11.h"
+#include "detail/common.h"
+
+PYBIND11_NAMESPACE_BEGIN(PYBIND11_NAMESPACE)
+
+PYBIND11_NAMESPACE_BEGIN(detail)
+
+inline bool PyWarning_Check(PyObject *obj) {
+    int result = PyObject_IsSubclass(obj, PyExc_Warning);
+    if (result == 1) {
+        return true;
+    }
+    if (result == -1) {
+        raise_from(PyExc_SystemError,
+                   "PyWarning_Check(): internal error of Python C API while "
+                   "checking a subclass of the object!");
+        throw error_already_set();
+    }
+    return false;
+}
+
+PYBIND11_NAMESPACE_END(detail)
+
+PYBIND11_NAMESPACE_BEGIN(warnings)
+
+inline object
+new_warning_type(handle scope, const char *name, handle base = PyExc_RuntimeWarning) {
+    if (!detail::PyWarning_Check(base.ptr())) {
+        pybind11_fail("warning(): cannot create custom warning, base must be a subclass of "
+                      "PyExc_Warning!");
+    }
+    if (hasattr(scope, "__dict__") && scope.attr("__dict__").contains(name)) {
+        pybind11_fail("Error during initialization: multiple incompatible "
+                      "definitions with name \""
+                      + std::string(name) + "\"");
+    }
+    std::string full_name = scope.attr("__name__").cast<std::string>() + std::string(".") + name;
+    handle h(PyErr_NewException(const_cast<char *>(full_name.c_str()), base.ptr(), nullptr));
+    object obj = reinterpret_steal<object>(h);
+    scope.attr(name) = obj;
+    return obj;
+}
+
+// Similar to Python `warnings.warn()`
+inline void
+warn(const char *message, handle category = PyExc_RuntimeWarning, int stack_level = 2) {
+    if (!detail::PyWarning_Check(category.ptr())) {
+        pybind11_fail("raise_warning(): cannot raise warning, category must be a subclass of "
+                      "PyExc_Warning!");
+    }
+
+    if (PyErr_WarnEx(category.ptr(), message, stack_level) == -1) {
+        throw error_already_set();
+    }
+}
+
+PYBIND11_NAMESPACE_END(warnings)
+
+PYBIND11_NAMESPACE_END(PYBIND11_NAMESPACE)

tests/CMakeLists.txt

@@ -162,7 +162,8 @@ set(PYBIND11_TEST_FILES
     test_unnamed_namespace_a
     test_unnamed_namespace_b
     test_vector_unique_ptr_member
-    test_virtual_functions)
+    test_virtual_functions
+    test_warnings)
 
 # Invoking cmake with something like:
 #     cmake -DPYBIND11_TEST_OVERRIDE="test_callbacks.cpp;test_pickling.cpp" ..

tests/test_warnings.cpp

@@ -0,0 +1,76 @@
+/*
+    tests/test_warnings.cpp -- usage of warnings::warn() and warnings categories.
+
+    Copyright (c) 2024 Jan Iwaszkiewicz <[email protected]>
+
+    All rights reserved. Use of this source code is governed by a
+    BSD-style license that can be found in the LICENSE file.
+*/
+
+#include <pybind11/warnings.h>
+
+#include "pybind11_tests.h"
+
+#include <utility>
+
+namespace warning_helpers {
+void warn_function(py::module &m, const char *name, py::handle category, const char *message) {
+    m.def(name, [category, message]() { py::warnings::warn(message, category); });
+}
+} // namespace warning_helpers
+
+class CustomWarning {};
+
+TEST_SUBMODULE(warnings_, m) {
+
+    // Test warning mechanism base
+    m.def("raise_and_return", []() {
+        std::string message = "Warning was raised!";
+        py::warnings::warn(message.c_str(), PyExc_Warning);
+        return 21;
+    });
+
+    m.def("raise_default", []() { py::warnings::warn("RuntimeWarning is raised!"); });
+
+    m.def("raise_from_cpython",
+          []() { py::warnings::warn("UnicodeWarning is raised!", PyExc_UnicodeWarning); });
+
+    m.def("raise_and_fail",
+          []() { py::warnings::warn("RuntimeError should be raised!", PyExc_Exception); });
+
+    // Test custom warnings
+    PYBIND11_CONSTINIT static py::gil_safe_call_once_and_store<py::object> ex_storage;
+    ex_storage.call_once_and_store_result([&]() {
+        return py::warnings::new_warning_type(m, "CustomWarning", PyExc_DeprecationWarning);
+    });
+
+    m.def("raise_custom", []() {
+        py::warnings::warn("CustomWarning was raised!", ex_storage.get_stored());
+        return 37;
+    });
+
+    // Bind warning categories
+    warning_helpers::warn_function(m, "raise_base_warning", PyExc_Warning, "This is Warning!");
+    warning_helpers::warn_function(
+        m, "raise_bytes_warning", PyExc_BytesWarning, "This is BytesWarning!");
+    warning_helpers::warn_function(
+        m, "raise_deprecation_warning", PyExc_DeprecationWarning, "This is DeprecationWarning!");
+    warning_helpers::warn_function(
+        m, "raise_future_warning", PyExc_FutureWarning, "This is FutureWarning!");
+    warning_helpers::warn_function(
+        m, "raise_import_warning", PyExc_ImportWarning, "This is ImportWarning!");
+    warning_helpers::warn_function(m,
+                                   "raise_pending_deprecation_warning",
+                                   PyExc_PendingDeprecationWarning,
+                                   "This is PendingDeprecationWarning!");
+    warning_helpers::warn_function(
+        m, "raise_resource_warning", PyExc_ResourceWarning, "This is ResourceWarning!");
+    warning_helpers::warn_function(
+        m, "raise_runtime_warning", PyExc_RuntimeWarning, "This is RuntimeWarning!");
+    warning_helpers::warn_function(
+        m, "raise_syntax_warning", PyExc_SyntaxWarning, "This is SyntaxWarning!");
+    warning_helpers::warn_function(
+        m, "raise_unicode_warning", PyExc_UnicodeWarning, "This is UnicodeWarning!");
+    warning_helpers::warn_function(
+        m, "raise_user_warning", PyExc_UserWarning, "This is UserWarning!");
+}

tests/test_warnings.py

@@ -0,0 +1,104 @@
+from __future__ import annotations
+
+import warnings
+
+import pytest
+
+import pybind11_tests  # noqa: F401
+from pybind11_tests import warnings_ as m
+
+
+@pytest.mark.parametrize(
+    ("expected_category", "expected_message", "expected_value", "module_function"),
+    [
+        (Warning, "Warning was raised!", 21, m.raise_and_return),
+        (RuntimeWarning, "RuntimeWarning is raised!", None, m.raise_default),
+        (UnicodeWarning, "UnicodeWarning is raised!", None, m.raise_from_cpython),
+    ],
+)
+def test_warning_simple(
+    expected_category, expected_message, expected_value, module_function
+):
+    with pytest.warns(Warning) as excinfo:
+        value = module_function()
+
+    assert issubclass(excinfo[0].category, expected_category)
+    assert str(excinfo[0].message) == expected_message
+    assert value == expected_value
+
+
+def test_warning_fail():
+    with pytest.raises(Exception) as excinfo:
+        m.raise_and_fail()
+
+    assert issubclass(excinfo.type, RuntimeError)
+    assert (
+        str(excinfo.value)
+        == "raise_warning(): cannot raise warning, category must be a subclass of PyExc_Warning!"
+    )
+
+
+def test_warning_register():
+    assert m.CustomWarning is not None
+    assert issubclass(m.CustomWarning, DeprecationWarning)
+
+    with pytest.warns(m.CustomWarning) as excinfo:
+        warnings.warn("This is warning from Python!", m.CustomWarning, stacklevel=1)
+
+    assert issubclass(excinfo[0].category, DeprecationWarning)
+    assert issubclass(excinfo[0].category, m.CustomWarning)
+    assert str(excinfo[0].message) == "This is warning from Python!"
+
+
+@pytest.mark.parametrize(
+    (
+        "expected_category",
+        "expected_base",
+        "expected_message",
+        "expected_value",
+        "module_function",
+    ),
+    [
+        (
+            m.CustomWarning,
+            DeprecationWarning,
+            "CustomWarning was raised!",
+            37,
+            m.raise_custom,
+        ),
+    ],
+)
+def test_warning_custom(
+    expected_category, expected_base, expected_message, expected_value, module_function
+):
+    with pytest.warns(expected_category) as excinfo:
+        value = module_function()
+
+    assert issubclass(excinfo[0].category, expected_base)
+    assert issubclass(excinfo[0].category, expected_category)
+    assert str(excinfo[0].message) == expected_message
+    assert value == expected_value
+
+
+@pytest.mark.parametrize(
+    ("expected_category", "module_function"),
+    [
+        (Warning, m.raise_base_warning),
+        (BytesWarning, m.raise_bytes_warning),
+        (DeprecationWarning, m.raise_deprecation_warning),
+        (FutureWarning, m.raise_future_warning),
+        (ImportWarning, m.raise_import_warning),
+        (PendingDeprecationWarning, m.raise_pending_deprecation_warning),
+        (ResourceWarning, m.raise_resource_warning),
+        (RuntimeWarning, m.raise_runtime_warning),
+        (SyntaxWarning, m.raise_syntax_warning),
+        (UnicodeWarning, m.raise_unicode_warning),
+        (UserWarning, m.raise_user_warning),
+    ],
+)
+def test_warning_categories(expected_category, module_function):
+    with pytest.warns(Warning) as excinfo:
+        module_function()
+
+    assert issubclass(excinfo[0].category, expected_category)
+    assert str(excinfo[0].message) == f"This is {expected_category.__name__}!"