Optionals that are somewhat positional

[biowpn]

Behavior 1

In gcc there is an option -x <language> that works as described:

Specify explicitly the language for the following input files

This means that while -x looks like an optional, it is positional and affect the following positionals:

gcc -xc file1 file2

is different from

gcc file1 -xc file2

Behavior 2

Furthermore, there are flags in the gcc/linker that affect the following options. Take --whole-archive:

gcc --whole-archive -lmylib1 --no-whole-archive -lmylib2

The above basically turns on whole-archive for mylib1, but not mylib2.

Question

Is there a way to emulate the above behaviors with CLI11?

Notes

I've searched to docs through and through and haven't found a good answer.

With behavior 1, I can somewhat get around with

vector<string> args;
CLI::App app;
app.add_option("file,-x", args);

Only 2 issues: no separate help messages for file and -x; one can't really tell whether an element in args is contributed by -x or file.

With behavior 2, there isn't much I can do about it.

Just my opinion: it would solve both cases if add_option and add_flag accept a callback that is invoked for each individual argument during the parsing stage. Something like:

vector<string> c_files;
vector<string> cxx_files;
vector<string>* curr = &c_files;

CLI::App app;
app.add_option("file", [&](const string& file) { 
  curr->push_back(file);
  return true;
});
app.add_option("-x", [&](const string& language) { 
  if (language == "c") { curr = &c_files; }
  else if (language == "c++) { curr = &cxx_files; }
  else { return false; }
  return true;
});

[phlptp]

You likely want to look at trigger_on_parse() this will execute the callback given for the option or flag when the option is parsed vs after all parsing is finished.

[biowpn]

You likely want to look at trigger_on_parse() this will execute the callback given for the option or flag when the option is parsed vs after all parsing is finished.

Thanks for the swift reply!

I can now get case 2 working. However, case 1 still doesn't work: callback for positional is invoked after parsing still.

Full test program attached below:

#include "CLI11.hpp"

int main(int argc, char** argv) {
    using namespace std;

    CLI::App app;
    app.add_option("file", "input file")
        ->take_all()
        ->allow_extra_args(true)
        ->each([&](string arg) { cout << "file callback invoked: " << arg << "\n"; })
        ->trigger_on_parse();
    app.add_option("-x", "specify the language for the following files")
        ->take_all()
        ->each([&](string arg) { cout << "-x callback invoked: " << arg << "\n"; })
        ->trigger_on_parse();
    CLI11_PARSE(app, argc, argv);

    return 0;
}

Compile and run:

$ g++ main.cpp
$ ./a.out  file1 -xc file2
-x callback invoked: c
file callback invoked: file1
file callback invoked: file2

I would expect

file callback invoked: file1
-x callback invoked: c
file callback invoked: file2

[biowpn]

By the way, the conan center still only has version 1.9.1: https://conan.io/center/CLI11

Edit: never mind, found https://conan.io/center/cli11

[phlptp]

I think this is issue is resolved in the latest release now that trigger_on_parse works for positional arguments as well