sokol_args: support single keys for native apps

[edubart]

I am using sokol_args.h as a library to handle command line arguments in an apps that can be compiled to WebAssembly or native (Linux in my case).
When I use emrun myapp.html -- -myarg, while the argument -myarg is listed for WebAssembly, it's omitted in native, so there is a different behavior between native and WebAssembly.

I noticed this comment in sokol_args.h:

Currently 'single keys' without values are not allowed, but may be in the future.

Actually single keys works in WebAssembly, but not in native yet, I guess this behavior was not really defined in the library. I think the library should start defining this, so native could be improved to handle single key arguments like WebAssembly is.

[floooh]

Agreed, I was actually missing it too a couple of times. It should essentially be a shortcut for boolean args (bla=true vs just bla). I guess the reason why I didn't implement this to begin with is that it complicates the parser (also because sokol-args doesn't expect args to start with '-')

[floooh]

Hmm ok, on the web it works by accident, because the URLSearchParams object fill missing values with empty strings, e.g. here:

sokol/sokol_args.h

Lines 723 to 724 in 751fc4c

	const key = p.value[0];
	const val = p.value[1];

const val will be an empty string.

I'll see if I can fix the 'native' arg parser function to work the same way.

PS: I probably still need to change behaviour a bit, because currently sargs_value() for a non-existing arg returns an empty string, so standalone args can't have an empty value string too.

[floooh]

Ok, fixed via #896

See the updated documentation for caveats (key-only args have an empty value string, but can be checked with sargs_exists() or sargs_boolean().

Also check the updated tests (

sokol/tests/functional/sokol_args_test.c

Lines 256 to 302 in 10f2c9c

	static char* argv_11[] = { "exe_name", "kvp0 kvp1", "kvp2 = val2", "kvp3", "kvp4=val4" };
	UTEST(sokol_args, key_only_args) {
	sargs_setup(&(sargs_desc){
	.argc = NUM_ARGS(argv_11),
	.argv = argv_11,
	});
	T(sargs_isvalid());
	T(sargs_num_args() == 5);
	T(0 == sargs_find("kvp0"));
	T(1 == sargs_find("kvp1"));
	T(2 == sargs_find("kvp2"));
	T(3 == sargs_find("kvp3"));
	T(4 == sargs_find("kvp4"))
	T(-1 == sargs_find("kvp5"));
	T(-1 == sargs_find("val2"));
	T(-1 == sargs_find("val4"));
	T(sargs_exists("kvp0"));
	T(sargs_exists("kvp1"));
	T(sargs_exists("kvp2"));
	T(sargs_exists("kvp3"));
	T(sargs_exists("kvp4"));
	T(!sargs_exists("kvp5"));
	TSTR(sargs_value("kvp0"), "");
	TSTR(sargs_value("kvp1"), "");
	TSTR(sargs_value("kvp2"), "val2");
	TSTR(sargs_value("kvp3"), "");
	TSTR(sargs_value("kvp4"), "val4");
	TSTR(sargs_value("kvp5"), "");
	TSTR(sargs_value_def("kvp0", "bla0"), "bla0");
	TSTR(sargs_value_def("kvp1", "bla1"), "bla1");
	TSTR(sargs_value_def("kvp2", "bla2"), "val2");
	TSTR(sargs_value_def("kvp3", "bla3"), "bla3");
	TSTR(sargs_value_def("kvp4", "bla4"), "val4");
	TSTR(sargs_value_def("kvp5", "bla5"), "bla5");
	TSTR(sargs_key_at(0), "kvp0");
	TSTR(sargs_key_at(1), "kvp1");
	TSTR(sargs_key_at(2), "kvp2");
	TSTR(sargs_key_at(3), "kvp3");
	TSTR(sargs_key_at(4), "kvp4");
	TSTR(sargs_key_at(5), "");
	TSTR(sargs_value_at(0), "");
	TSTR(sargs_value_at(1), "");
	TSTR(sargs_value_at(2), "val2");
	TSTR(sargs_value_at(3), "");
	TSTR(sargs_value_at(4), "val4");
	TSTR(sargs_value_at(5), "");
	}

)

[edubart]

Thanks for improving this @floooh !