public static bool IsCustomRequired(this Arg argument) => argument?.CustomAttributes.OfType <RequiredAttribute>().Any() ?? false;
private void MakeCallable(MethodInfo mi, object inst, out Delegate cbl, out IReadOnlyList <CommandArgument> args)
{
if (!mi.IsCommandCandidate(out var ps))
{
throw new MissingMethodException("Specified method is not suitable for a command.");
}
var ei = Expression.Constant(inst);
var ea = new ParameterExpression[ps.Length];
ea[0] = Expression.Parameter(typeof(CommandContext), "ctx");
var i = 1;
var ps1 = ps.Skip(1);
var argsl = new List <CommandArgument>(ps.Length - 1);
foreach (var xp in ps1)
{
var ca = new CommandArgument
{
Name = xp.Name,
Type = xp.ParameterType,
IsOptional = xp.IsOptional,
DefaultValue = xp.IsOptional ? xp.DefaultValue : null
};
var attrs = xp.GetCustomAttributes();
foreach (var xa in attrs)
{
switch (xa)
{
case DescriptionAttribute d:
ca.Description = d.Description;
break;
case RemainingTextAttribute r:
ca.IsCatchAll = true;
break;
case ParamArrayAttribute p:
ca.IsCatchAll = true;
ca.Type = xp.ParameterType.GetElementType();
ca._is_array = true;
break;
}
}
if (i > 1 && !ca.IsOptional && !ca.IsCatchAll && argsl[i - 2].IsOptional)
{
throw new InvalidOperationException("Non-optional argument cannot appear after an optional one");
}
argsl.Add(ca);
ea[i++] = Expression.Parameter(xp.ParameterType, xp.Name);
}
var ec = Expression.Call(ei, mi, ea);
var el = Expression.Lambda(ec, ea);
cbl = el.Compile();
args = new ReadOnlyCollection <CommandArgument>(argsl);
}