Restrict allowed values

In some cases an argument can receive one of the limited set of values. This can be achieved by adding .AllowedValues() to UDA:

import argparse;

struct T
{
    @(NamedArgument.AllowedValues("apple","pear","banana"))
    string fruit;
}

T t;
assert(CLI!T.parseArgs(t, ["--fruit", "apple"]));
assert(t == T("apple"));

// "kiwi" is not allowed
assert(!CLI!T.parseArgs(t, ["--fruit", "kiwi"]));

For the value that is not in the allowed list, this error will be printed:

Last modified: 22 March 2025