Expose __cpp_noexcept_function_type to Python tests and use explicit skip guards.

This replaces hasattr-based optional assertions with skipif-gated noexcept-only tests so skipped coverage is visible in pytest output while keeping non-noexcept checks always active.

Co-authored-by: Cursor <cursoragent@cursor.com>

Author: rwgk

tests/pybind11_tests.cpp

@@ -105,6 +105,12 @@ PYBIND11_MODULE(pybind11_tests, m, py::mod_gil_not_used()) {
     m.attr("detailed_error_messages_enabled") = false;
 #endif
 
+#if defined(__cpp_noexcept_function_type)
+    m.attr("defined___cpp_noexcept_function_type") = true;
+#else
+    m.attr("defined___cpp_noexcept_function_type") = false;
+#endif
+
     py::class_<UserType>(m, "UserType", "A `py::class_` type for testing")
         .def(py::init<>())
         .def(py::init<int>())

tests/test_buffers.py

@@ -7,7 +7,7 @@
 import pytest
 
 import env
-from pybind11_tests import ConstructorStats
+from pybind11_tests import ConstructorStats, defined___cpp_noexcept_function_type
 from pybind11_tests import buffers as m
 
 np = pytest.importorskip("numpy")
@@ -446,17 +446,26 @@ def test_ref_qualified_def_buffer():
     assert carr.shape == (4,)
     assert carr.flags["WRITEABLE"] is False
 
-    # noexcept ref-qualified forms are available only when noexcept is part of function type
-    if hasattr(m, "OneDBufferLRefNoexcept"):
-        nbuf = m.OneDBufferLRefNoexcept(3)
-        narr = np.frombuffer(nbuf, dtype=np.float32)
-        assert narr.shape == (3,)
-        narr[2] = 7.0
-        narr2 = np.frombuffer(nbuf, dtype=np.float32)
-        assert narr2[2] == pytest.approx(7.0)
-
-    if hasattr(m, "OneDBufferConstLRefNoexcept"):
-        ncbuf = m.OneDBufferConstLRefNoexcept(2)
-        ncarr = np.frombuffer(ncbuf, dtype=np.float32)
-        assert ncarr.shape == (2,)
-        assert ncarr.flags["WRITEABLE"] is False
+
+@pytest.mark.skipif(
+    not defined___cpp_noexcept_function_type,
+    reason="Requires __cpp_noexcept_function_type",
+)
+def test_ref_qualified_noexcept_def_buffer():
+    """Test issue #2234 follow-up: def_buffer with noexcept ref-qualified member pointers.
+
+    Covers:
+      - def_buffer(Return (Class::*)(Args...) & noexcept)
+      - def_buffer(Return (Class::*)(Args...) const & noexcept)
+    """
+    nbuf = m.OneDBufferLRefNoexcept(3)
+    narr = np.frombuffer(nbuf, dtype=np.float32)
+    assert narr.shape == (3,)
+    narr[2] = 7.0
+    narr2 = np.frombuffer(nbuf, dtype=np.float32)
+    assert narr2[2] == pytest.approx(7.0)
+
+    ncbuf = m.OneDBufferConstLRefNoexcept(2)
+    ncarr = np.frombuffer(ncbuf, dtype=np.float32)
+    assert ncarr.shape == (2,)
+    assert ncarr.flags["WRITEABLE"] is False

tests/test_methods_and_attributes.py

@@ -5,7 +5,7 @@
 import pytest
 
 import env
-from pybind11_tests import ConstructorStats
+from pybind11_tests import ConstructorStats, defined___cpp_noexcept_function_type
 from pybind11_tests import methods_and_attributes as m
 
 NO_GETTER_MSG = (
@@ -555,8 +555,6 @@ def test_rvalue_ref_qualified_methods():
     Covers:
       - Return (Class::*)(Args...) &&              (take)
       - Return (Class::*)(Args...) const &&        (peek)
-      - Return (Class::*)(Args...) && noexcept     (take_noexcept, C++17 only)
-      - Return (Class::*)(Args...) const && noexcept (peek_noexcept, C++17 only)
     """
     obj = m.RValueRefDerived()
     # && moves m_payload: first call gets the value, second gets empty string
@@ -565,14 +563,24 @@ def test_rvalue_ref_qualified_methods():
     # const && doesn't move: peek() is stable across calls
     assert obj.peek() == 77
     assert obj.peek() == 77
-    # noexcept variants are bound only under C++17; skip gracefully if absent
-    if hasattr(obj, "take_noexcept"):
-        obj2 = m.RValueRefDerived()
-        assert obj2.take_noexcept() == "rref_payload"
-        assert obj2.take_noexcept() == ""
-    if hasattr(obj, "peek_noexcept"):
-        assert obj.peek_noexcept() == 77
-        assert obj.peek_noexcept() == 77
+
+
+@pytest.mark.skipif(
+    not defined___cpp_noexcept_function_type,
+    reason="Requires __cpp_noexcept_function_type",
+)
+def test_noexcept_rvalue_ref_qualified_methods():
+    """Test noexcept rvalue-ref-qualified methods from an unregistered base.
+
+    Covers:
+      - Return (Class::*)(Args...) && noexcept       (take_noexcept)
+      - Return (Class::*)(Args...) const && noexcept (peek_noexcept)
+    """
+    obj = m.RValueRefDerived()
+    assert obj.take_noexcept() == "rref_payload"
+    assert obj.take_noexcept() == ""
+    assert obj.peek_noexcept() == 77
+    assert obj.peek_noexcept() == 77
 
 
 def test_noexcept_overload_cast():
@@ -612,14 +620,25 @@ def test_ref_qualified_overload_cast():
     assert obj.method_rref(1.0) == "(float) &&"
     assert obj.method_const_rref(1.0) == "(float) const &&"
 
-    if hasattr(obj, "method_lref_noexcept"):
-        assert obj.method_lref_noexcept(1) == "(long) & noexcept"
-    if hasattr(obj, "method_const_lref_noexcept"):
-        assert obj.method_const_lref_noexcept(1) == "(long) const & noexcept"
-    if hasattr(obj, "method_rref_noexcept"):
-        assert obj.method_rref_noexcept(1.0) == "(double) && noexcept"
-    if hasattr(obj, "method_const_rref_noexcept"):
-        assert obj.method_const_rref_noexcept(1.0) == "(double) const && noexcept"
+
+@pytest.mark.skipif(
+    not defined___cpp_noexcept_function_type,
+    reason="Requires __cpp_noexcept_function_type",
+)
+def test_noexcept_ref_qualified_overload_cast():
+    """Test issue #2234 follow-up: overload_cast with noexcept ref-qualified member pointers.
+
+    Covers:
+      - overload_cast_impl::operator()(Return (Class::*)(Args...) & noexcept, false_type)
+      - overload_cast_impl::operator()(Return (Class::*)(Args...) const & noexcept, true_type)
+      - overload_cast_impl::operator()(Return (Class::*)(Args...) && noexcept, false_type)
+      - overload_cast_impl::operator()(Return (Class::*)(Args...) const && noexcept, true_type)
+    """
+    obj = m.RefQualifiedOverloaded()
+    assert obj.method_lref_noexcept(1) == "(long) & noexcept"
+    assert obj.method_const_lref_noexcept(1) == "(long) const & noexcept"
+    assert obj.method_rref_noexcept(1.0) == "(double) && noexcept"
+    assert obj.method_const_rref_noexcept(1.0) == "(double) const && noexcept"
 
 
 def test_ref_qualified():

tests/test_numpy_vectorize.py

@@ -2,6 +2,7 @@
 
 import pytest
 
+from pybind11_tests import defined___cpp_noexcept_function_type
 from pybind11_tests import numpy_vectorize as m
 
 np = pytest.importorskip("numpy")
@@ -261,10 +262,23 @@ def test_ref_qualified_method_vectorization():
     assert np.all(o.method_lref(x, y) == [[14, 15], [24, 25]])
     assert np.all(o.method_const_lref(x, y) == [[14, 15], [24, 25]])
 
-    if hasattr(o, "method_lref_noexcept"):
-        assert np.all(o.method_lref_noexcept(x, y) == [[14, 15], [24, 25]])
-    if hasattr(o, "method_const_lref_noexcept"):
-        assert np.all(o.method_const_lref_noexcept(x, y) == [[14, 15], [24, 25]])
+
+@pytest.mark.skipif(
+    not defined___cpp_noexcept_function_type,
+    reason="Requires __cpp_noexcept_function_type",
+)
+def test_noexcept_ref_qualified_method_vectorization():
+    """Test issue #2234 follow-up: vectorize with noexcept lvalue-ref-qualified member pointers.
+
+    Covers:
+      - vectorize(Return (Class::*)(Args...) & noexcept)
+      - vectorize(Return (Class::*)(Args...) const & noexcept)
+    """
+    o = m.VectorizeTestClass(3)
+    x = np.array([1, 2], dtype="int")
+    y = np.array([[10], [20]], dtype="float32")
+    assert np.all(o.method_lref_noexcept(x, y) == [[14, 15], [24, 25]])
+    assert np.all(o.method_const_lref_noexcept(x, y) == [[14, 15], [24, 25]])
 
 
 def test_noexcept_method_vectorization():