[GRASS-dev] Added suppress_required field to flags

[Glynn Clements]

Martin Landa wrote:

> > However, this feature cannot be used until the GUI's own requirement
> > checking has been adapted to understand it. Currently, if an option
> > marked as ->required is omitted but a flag marked as
> > ->suppress_required is given, the command itself won't complain about
> > the missing option but the GUI will.
> >
> > The field is included in the --interface-description output; the GUI
> > just needs to be updated to make use of it.
> `
> done in r44422.

Okay. If people know of more cases where options are being listed as
->required=NO for the sake of special cases, or where certain flags
require option=dummy to satisfy the requirements, please mention them
(or fix them). There isn't any way to identify such cases
mechanically.

The situation with g.mapsets will require a more complex solution,
i.e. some way to inform the parser that at least one option from a set
is required.

One possibility is to allow the module to supply a boolean expression
involving option/flag names which must evaluate to true. This would
allow all of:

+ At least one of ... must be given
+ At most one of ... must be given
+ If ... is given, ... must also be given
+ If ... is given, ... must not be given

However, a more restrictive form might be more useful to the GUI. 

Specifically, one or more lists of alternatives, where each
alternative identifies a primary flag/option, along with any
constraints on other options. This would allow a group of radio
buttons to be attached to the primary options.

E.g. for g.mapsets, the mapset=, addmapset= and removemapset= options
would form a group (along with the -s flag and possibly the -l flag). 
So the user would be able to select exactly one of them, and the
others would be greyed out.

-- 
Glynn Clements <glynn at gclements.plus.com>