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On Wednesday, 13 October 2021 at 16:24:52 UTC, Steven Schveighoffer wrote:
>The point is that I shouldn't have to tell the library the name of something that I've already given a name to.
Having them named differently on the command line than the actual field name should still be a possibility (and required in some cases, e.g. the enum case above), but honestly, the Params struct exists solely to accept command line parameters, there's no compelling need to use alternate names for the command line and the field name. If the library automatically does the right thing by default, then your code becomes simpler and more beautiful.
Not to detract from your library, because I think it's an awesome design to model using structs (one I use all the time), but the API developer in me frowns at lack of DRY. Try to focus on requiring the smallest amount of machinery/attributes possible. Every time you require extraneous pieces to get things to work, it adds another place where errors/confusion can happen.
I got your point. Omitting the name is good suggestion and I'll add this.
Regarding the detecting all members and treating them as an arguments, I see one issues so far: the struct might have other members that are not used in CLI (it can be even functions).
Consider the example when the member is renamed but the struct still provides the old name for backward compatibility:
struct T
{
string name;
@property string label() const { return name; }
}
pragma(msg, __traits(allMembers, T)); // tuple("name", "label")
Another example is when the struct has additional functions convenient for the users so it's not clear whether void foo() is a CLI flag or just a convenient function.
So to implement your suggestion correctly, argparse should provide a way to opt-out specific members from CLI.
In addition to that, each CLI argument usually has its own help text so in most cases each member will have an UDA with this text which makes opt-out approach mush less useful. So it sill look like this at the end:
struct T
{
@help("First name")
string firstName;
@help("Last name")
string lastName;
@skip
@property string fullName() const { return firstName~" "~lastName; }
}
