RFE: add version number support to `platforms` field in portfiles

[cooljeanius (Eric Gallager)]

Thought of this is #38506; not sure if there's already a ticket open for it...

Anyway, currently, if a port is incompatible with a certain OS version, the portfile author has to write something like this:

pre-fetch {
    if {${os.platform} == "darwin" && ${os.major} < 9} {
        ui_error "${name} is only supported on OS X 10.5 Leopard or later."
        return -code error "unsupported platform version"
    }
}

It'd be much easier to just be able to write something likeplatforms darwin 9+ or something like that instead.

[larryv (Lawrence Velázquez)]

I’ve been thinking about this. I’m leaning towards a syntax similar to that in compiler_blacklist_versions.

platforms   macosx {darwin >= 9} freebsd

[cooljeanius (Eric Gallager)]

Replying to larryv@…:

I’ve been thinking about this. I’m leaning towards a syntax similar to that in compiler_blacklist_versions.

platforms   macosx {darwin >= 9} freebsd

That would be perfect, thanks for agreeing to take this on.

[larryv (Lawrence Velázquez)]

Hm. It doesn’t seem that platforms even affects whether or not a port can be installed. Even after I change a port to use

platforms   freebsd

I can still install it on OS X. Can anyone confirm this behavior?

[raimue (Rainer Müller)]

The platform field is currently purely informational and is not enforced.

Duplicate of #15712.

[larryv (Lawrence Velázquez)]

Replying to raimue@…:

The platform field is currently purely informational and is not enforced.

Would changing this cause any problems?