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Improve make_tuple error message under debugging

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When make_tuple fails (for example, when print() is called with a
non-convertible argument, as in #778) the error message a less helpful
than it could be:

    make_tuple(): unable to convert arguments of types 'std::tuple<type1, type2>' to Python object

There is no actual std::tuple involved (only a parameter pack and a
Python tuple), but it also doesn't immediately reveal which type caused
the problem.

This commit changes the debugging mode output to show just the
problematic type:

    make_tuple(): unable to convert argument of type 'type2' to Python object
This commit is contained in:
Jason Rhinelander
2017-04-05 10:51:02 -04:00
parent 8f010cce8e
commit 6906b270d6
3 changed files with 23 additions and 6 deletions
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11
include/pybind11/cast.h
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@@ -1246,18 +1246,19 @@ NAMESPACE_END(detail)
template <return_value_policy policy = return_value_policy::automatic_reference,
typename... Args> tuple make_tuple(Args&&... args_) {
const size_t size = sizeof...(Args);
constexpr size_t size = sizeof...(Args);
std::array<object, size> args {
{ reinterpret_steal<object>(detail::make_caster<Args>::cast(
std::forward<Args>(args_), policy, nullptr))... }
};
for (auto &arg_value : args) {
if (!arg_value) {
for (size_t i = 0; i < args.size(); i++) {
if (!args[i]) {
#if defined(NDEBUG)
throw cast_error("make_tuple(): unable to convert arguments to Python object (compile in debug mode for details)");
#else
throw cast_error("make_tuple(): unable to convert arguments of types '" +
(std::string) type_id<std::tuple<Args...>>() + "' to Python object");
std::array<std::string, size> argtypes { type_id<Args>()... };
throw cast_error("make_tuple(): unable to convert argument of type '" +
argtypes[i] + "' to Python object");
#endif
}
}