Address comments

Author: virtuald

include/pybind11/cast.h

@@ -1019,12 +1019,12 @@ type_caster<T, SFINAE> &load_type(type_caster<T, SFINAE> &conv, const handle &ha
 #if !defined(PYBIND11_DETAILED_ERROR_MESSAGES)
         throw cast_error(
             "Unable to cast Python instance of type "
-            + static_cast<std::string>(str(type::handle_of(handle)))
+            + str(type::handle_of(handle)).cast<std::string>()
             + " to C++ type '?' (#define "
               "PYBIND11_DETAILED_ERROR_MESSAGES or compile in debug mode for details)");
 #else
         throw cast_error("Unable to cast Python instance of type "
-                         + (std::string) str(type::handle_of(handle)) + " to C++ type '"
+                         + str(type::handle_of(handle)).cast<std::string>() + " to C++ type '"
                          + type_id<T>() + "'");
 #endif
     }
@@ -1088,13 +1088,13 @@ detail::enable_if_t<!detail::move_never<T>::value, T> move(object &&obj) {
     if (obj.ref_count() > 1) {
 #if !defined(PYBIND11_DETAILED_ERROR_MESSAGES)
         throw cast_error(
-            "Unable to cast Python " + (std::string) str(type::handle_of(obj))
+            "Unable to cast Python " + str(type::handle_of(obj)).cast<std::string>()
             + " instance to C++ rvalue: instance has multiple references"
               " (#define PYBIND11_DETAILED_ERROR_MESSAGES or compile in debug mode for details)");
 #else
-        throw cast_error("Unable to move from Python " + (std::string) str(type::handle_of(obj))
-                         + " instance to C++ " + type_id<T>()
-                         + " instance: instance has multiple references");
+        throw cast_error("Unable to move from Python "
+                         + str(type::handle_of(obj)).cast<std::string>() + " instance to C++ "
+                         + type_id<T>() + " instance: instance has multiple references");
 #endif
     }
 

include/pybind11/detail/common.h

@@ -1225,7 +1225,7 @@ constexpr
 #endif
 
 // Pybind offers detailed error messages by default for all builts that are debug (through the
-// negation of ndebug). This can also be manually enabled by users, for any builds, through
+// negation of NDEBUG). This can also be manually enabled by users, for any builds, through
 // defining PYBIND11_DETAILED_ERROR_MESSAGES.
 //
 // Pybind attempts to provide useful error messages by default. Specifically, this macro will

tests/test_callbacks.py

@@ -5,6 +5,7 @@
 
 import env  # noqa: F401
 from pybind11_tests import callbacks as m
+from pybind11_tests import detailed_error_messages_enabled
 
 
 def test_callbacks():
@@ -70,11 +71,19 @@ def f(*args, **kwargs):
 
     with pytest.raises(RuntimeError) as excinfo:
         m.test_arg_conversion_error1(f)
-    assert "Unable to convert call argument" in str(excinfo.value)
+    assert str(excinfo.value) == "Unable to convert call argument " + (
+        "'1' of type 'UnregisteredType' to Python object"
+        if detailed_error_messages_enabled
+        else "'1' to Python object (#define PYBIND11_DETAILED_ERROR_MESSAGES or compile in debug mode for details)"
+    )
 
     with pytest.raises(RuntimeError) as excinfo:
         m.test_arg_conversion_error2(f)
-    assert "Unable to convert call argument" in str(excinfo.value)
+    assert str(excinfo.value) == "Unable to convert call argument " + (
+        "'expected_name' of type 'UnregisteredType' to Python object"
+        if detailed_error_messages_enabled
+        else "'expected_name' to Python object (#define PYBIND11_DETAILED_ERROR_MESSAGES or compile in debug mode for details)"
+    )
 
 
 def test_lambda_closure_cleanup():

tests/test_exceptions.cpp

@@ -340,8 +340,8 @@ TEST_SUBMODULE(exceptions, m) {
         return py::str("UNEXPECTED");
     });
 
-    m.def("test_hidden_error", [](const py::function &fn) {
-        // function returns none instead of int, should give a useful error message
+    m.def("test_fn_cast_int", [](const py::function &fn) {
+        // function returns None instead of int, should give a useful error message
         fn().cast<int>();
     });
 }

tests/test_exceptions.py

@@ -383,11 +383,10 @@ def test_pypy_oserror_normalization():
     assert "this_filename_must_not_exist" in what
 
 
-def test_sane_hidden_exception():
+def test_fn_cast_int_exception():
     with pytest.raises(RuntimeError) as excinfo:
-        m.test_hidden_error(lambda: None)
+        m.test_fn_cast_int(lambda: None)
 
-    # Always display the python type even if the C++ type isn't available
     assert str(excinfo.value).startswith(
         "Unable to cast Python instance of type <class 'NoneType'> to C++ type"
     )