[jira] [Created] (MESOS-2711) Add some commonly-used utility to stout/flags

["Marco Massenzio (JIRA)" <ji...@apache.org>]

Marco Massenzio created MESOS-2711:
--------------------------------------

             Summary: Add some commonly-used utility to stout/flags
                 Key: MESOS-2711
                 URL: https://issues.apache.org/jira/browse/MESOS-2711
             Project: Mesos
          Issue Type: Improvement
          Components: stout
    Affects Versions: 0.22.0
            Reporter: Marco Massenzio
            Assignee: Marco Massenzio
            Priority: Minor


When using {{stout/flags/flags.hpp}} and implementing our own {{Flags}} class (derived from {{flags::FlagsBase}}) pretty much everyone ends up re-implementing some variant of the following:

{code}
void printUsage(const string& prog, const string& flags)
{
  cout << "Usage: " << os::basename(prog).get() << " [options]\n\n"
      "One (and only one) of the following options MUST be present.\n\n"
      "Options:\n" << flags << endl;
}
{code}

and in {{main.cpp}}:
{code}
int main(int argc, char** argv)
{
  MyFlags flags;
  bool help;
  flags.add(&help, "help", "Prints this help message", false);

  Try<Nothing> load = flags.load(None(), argc, argv);
  // ...
  if (help) {
      printUsage(argv[0], flags.usage());
  }
  // ...
}
{code}

Note that {{FlagsBase}} already "knows" {{argv[0]}} and it would be nice it implemented the "help" functionality itself, so that everyone immediately gains access to it; further, the {{printUsage()}} method could be implemented easily by simply adding the facility for derived classes to specify some form of a "blurb" (the bit that is emitted between the {{Usage:}} line and the {{Options:}} body and, possibly, to customize the "usage" one-liner.



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