Parsing error if \t in default (is this normal?)

[acourdavault]

Hello,

Issue:
Cannot parse default of my options, i get null, null
I am using Visual Community v14,
Usage is:

R"(test_ua_client

    Usage:
      test_ua_client [--host=<host>] [--port=<port>]

    Options:
      --host=<host>		Host [default: localhost].
      --port=<port>		Port [default: 53530].
)"

I tried to debug and in this piece of code (below) i ve noticed that:

• the "double space" is not found. And indeed the double space was trimmed before somehow,
• the options_end is ""
• when parsing this: std::regex{"\[default: (.*)\]" there is no match
  • description is "--host=\t\tHost [default: localhost]."

from my understanding, this is where localhost should have been parsed

If I replace "\t" by spaces there is no issue.
I thought this should have worked?

inline Option Option::parse(std::string const& option_description)
	{
		std::string shortOption, longOption;
		int argcount = 0;
		value val { false };

		auto double_space = option_description.find("  ");
		auto options_end = option_description.end();
		if (double_space != std::string::npos) {
			options_end = option_description.begin() + static_cast<std::ptrdiff_t>(double_space);
		}
// .....

		if (argcount) {
			std::smatch match;
			if (std::regex_search(options_end, option_description.end(),
						  match,
						  std::regex{"\\[default: (.*)\\]", std::regex::icase}))
			{
				val = match[1].str();
			}
		}