Correct vertical alignment for multi-line help message

[fanurs]

Issue

Currently, a multi-line help message would look something like:

Positional arguments:
  program_inputs        This is the first line of help text.
And this is the second line of help text. (MISALIGNED)

Optional arguments:
  -h, --help            shows help message and exits 
  -v, --version         prints version information and exits 

This is produced from the C++ code:

argparse::ArgumentParser program("program");
program.add_argument("program_inputs")
    .help(
        "This is the first line of help text.\n"
        "And this is the second line of help text."
    );

Expecting

Is it possible to make the multi-line help message aligns properly?

Positional arguments:
  program_inputs        This is the first line of help text.
                        And this is the second line of help text. (ALIGNED)

Optional arguments:
  -h, --help            shows help message and exits 
  -v, --version         prints version information and exits 

If not, is there a way, as a hack, to access the number of spaces needed to add prior to the second line of the help message?

Thank you.

[p-ranav]

I am not aware of a hack but the relevant code is here and it wouldn't take much to implement support.

I'd imagine something like this:

const auto name_string = name_stream.str();
stream << name_string;

auto prefix = std::string(name_string.size(), ' ') + "\t";
auto first_line = true;
auto pos = 0;
auto prev = 0;
while ((pos = argument.m_help.find('\n', prev)) != std::string::npos) {
    auto line = argument.m_help.substr(prev, pos - prev);

    // Print nth line of help message

    if (first_line) {
        // First line
        first_line = false;
        stream << "\t" << line << "\n"; 
    } else {
        // Second, Third... (N-1)th line of help message
        stream << prefix << line << "\n";
    }
    prev = pos + 1;
}
if (first_line) {
    // Print first and only line of help if no '\n' in help message
    stream << "\t" << line;
} else {
    // Print last line of help message in a multi-line help
    stream << prefix << argument.m_help.substr(prev);  
}

I'm not sure if this will fail since I've not tested anything. But I'd be open to a PR with a clean and tested implementation.

[fanurs]

Thanks for the quick and detailed reply. I will try working on a PR to support this feature / fix then.

[nmoreaud]

This doesn't seem to work for optional arguments