Add support for nested exceptions in custom exceptions

include/pybind11/pybind11.h

@@ -2535,7 +2535,9 @@ class exception : public object {
     }
 
     // Sets the current python exception to this exception object with the given message
-    void operator()(const char *message) { PyErr_SetString(m_ptr, message); }
+    void operator()(const char *message) {
+        detail::raise_err(m_ptr, message);
+    }
 };
 
 PYBIND11_NAMESPACE_BEGIN(detail)
@@ -2567,6 +2569,8 @@ register_exception_impl(handle scope, const char *name, handle base, bool isLoca
         try {
             std::rethrow_exception(p);
         } catch (const CppException &e) {
+            detail::handle_nested_exception(e, p);
+
             detail::get_exception_object<CppException>()(e.what());
         }
     });

tests/test_exceptions.cpp

@@ -305,6 +305,14 @@ TEST_SUBMODULE(exceptions, m) {
         }
     });
 
+    m.def("throw_custom_nested_exception", []() {
+        try {
+            throw std::runtime_error("Inner Exception");
+        } catch (const std::runtime_error &) {
+            std::throw_with_nested(MyException5("Outer Exception"));
+        }
+    });
+
     m.def("error_already_set_what", [](const py::object &exc_type, const py::object &exc_value) {
         PyErr_SetObject(exc_type.ptr(), exc_value.ptr());
         std::string what = py::error_already_set().what();

tests/test_exceptions.py

@@ -248,6 +248,13 @@ def test_throw_nested_exception():
     assert str(excinfo.value.__cause__) == "Inner Exception"
 
 
+def test_throw_custom_nested_exception():
+    with pytest.raises(m.MyException5) as excinfo:
+        m.throw_custom_nested_exception()
+    assert str(excinfo.value) == "Outer Exception"
+    assert str(excinfo.value.__cause__) == "Inner Exception"
+
+
 # This can often happen if you wrap a pybind11 class in a Python wrapper
 def test_invalid_repr():
     class MyRepr: