Variants handling: my $0.02.

[Rainer Müller]

N_Ox wrote:
> These two sugar syntaxes would make the variant writing process cleaner.
> But maybe they could help us more...
> 
> Let's say the variants which do something only when they are disabled 
> (variant -some_variant) are always enabled by default.
> In this setup, `sudo port install some_port +another_variant` would 
> install some_port @some_version+another_variant+some_variant.
> 
> In the registry, we would save "some_variant another_variant" as the 
> list of selected variants.
> 
> Now, let's explicitely disable the variant: sudo port install some_port 
> -some_variant +another_variant.
> In the registry, we would save "-some_variant another_variant".

Should the selection of -some_variant be user visible or just stored 
internal?
port installed some_port
  1) some_port at 1.0+another_variant-some_variant
  2) some_port at 1.0+another_variant

The main problem about default_variants in it's current implementation 
is that we don't store disabled variants and re-select them on upgrade...

> No need to use default_variants.

So how would I tell that a +variant is default? E.g. the lynx port 
provides support for OpenSSL (+ssl) and GNU TLS (+gnutls). They are 
conflicting variants, with +ssl in default_variants. But the user has 
the choice to install it with GNU TLS by using -ssl +gnutls.

But how would I write that in the new syntax?

> No more "Why the hell this variant is enabled when I upgrade this port?" 
> whining.
> No more "no_x11" variant:
> 
> variant -x11 {
>     # no x11
> } else {
>     # x11
> }

And which of those will be the default...? You said -some_variant will 
be enabled by default, or did I understand that wrong? In which cases 
will -some_variant be enabled by defaul? If it got no else-block?
I think that will end up more complex than it currently is...

Also, what is the difference between these and which one is a default 
variant?

variant foo {
    # do something
}

variant -bar {
    # do something
} else {
    # do something
}

variant -baz {
    # do something
}

What if we add some new flag? I like the idea of variant -some_variant, 
but maybe we could also add a default keyword which says if this variant 
is going to be installed by default.

Like this:
variant x11 description {Install X11 support} default {
    # x11
} else {
    # no x11
}

I like the overall idea to simplify the default variants handling!

Rainer