Added noconvert support for arg/return type hints

Author: timohl

include/pybind11/pybind11.h

@@ -497,8 +497,10 @@ class cpp_function : public function {
             } else if (c == '@') {
                 // Handle types that differ depending on whether they appear
                 // in an argument or a return value position
+                // For named arguments (py::arg()) with noconvert set, use return value type
                 ++pc;
-                if (!is_return_value) {
+                if (!is_return_value
+                    && !(arg_index < rec->args.size() && !rec->args[arg_index].convert)) {
                     while (*pc && *pc != '@')
                         signature += *pc++;
                     if (*pc == '@')

tests/test_pytypes.cpp

@@ -161,7 +161,11 @@ struct type_caster<RealNumber> {
         return py::float_(number.value).release();
     }
 
-    bool load(handle src, bool) {
+    bool load(handle src, bool convert) {
+        // If we're in no-convert mode, only load if given a float
+        if (!convert && !py::isinstance<py::float_>(src)) {
+            return false;
+        }
         if (!py::isinstance<py::float_>(src) && !py::isinstance<py::int_>(src)) {
             return false;
         }
@@ -1067,6 +1071,14 @@ TEST_SUBMODULE(pytypes, m) {
     m.attr("defined___cpp_inline_variables") = false;
 #endif
     m.def("half_of_number", [](const RealNumber &x) { return RealNumber{x.value / 2}; });
+    m.def(
+        "half_of_number_convert",
+        [](const RealNumber &x) { return RealNumber{x.value / 2}; },
+        py::arg("x"));
+    m.def(
+        "half_of_number_noconvert",
+        [](const RealNumber &x) { return RealNumber{x.value / 2}; },
+        py::arg("x").noconvert());
     // std::vector<T>
     m.def("half_of_number_vector", [](const std::vector<RealNumber> &x) {
         std::vector<RealNumber> result;

tests/test_pytypes.py

@@ -1195,6 +1195,13 @@ def test_final_annotation() -> None:
 
 def test_arg_return_type_hints(doc):
     assert doc(m.half_of_number) == "half_of_number(arg0: Union[float, int]) -> float"
+    assert (
+        doc(m.half_of_number_convert)
+        == "half_of_number_convert(x: Union[float, int]) -> float"
+    )
+    assert (
+        doc(m.half_of_number_noconvert) == "half_of_number_noconvert(x: float) -> float"
+    )
     assert m.half_of_number(2.0) == 1.0
     assert m.half_of_number(2) == 1.0
     assert m.half_of_number(0) == 0