Hi Llew,
The version of Boost.program_options I am using throws lots of informative exceptions to indicate precisely what has gone wrong.
The exception is where an incorrect argument to an option has been supplied
e.g. --some_arg "abc" where --some_arg 0.6 is expected.
The error message is annoyingly non-descript and it can be difficult to figure out which particular optional argument has been mis-specified.
I agree with you.
This imprecision is because when program_options::validation_error is being thrown, it is not clear which option is being parsed.
Could I suggest that this particular exception is caught in: void store(const parsed_options& options, variables_map& xm, bool utf8) and the option context added back in (and the same exception type re-thrown):
catch ( validation_error& e ) { throw validation_error("[--" + name + "]: " + e.what()); }
}
... }
What do you think?
Personally, I would prefer something like: catch(validation_error& e) { e.set_option_name(name); throw; } However, that would require to format the string inside the 'what' method, something like: class validation_error { std::string m_option_name; std::string m_error_message; const char* what() const { m_error_message = logic_error::what(); if (!m_option_name.empty()) m_error_message = "--" + m_option_name + " : " + m_error_message; return m_error_message.c_str(); } }; I've used this approach once, but I'm not sure if has any hidden problems. I'd appreciate if some exception handling expert could comment on this. Thanks, Volodya