[MacPorts] #15712: Add versions to platforms

[MacPorts]

#15712: Add versions to platforms
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  Reporter:  raimue       |      Owner:  larryv
      Type:  enhancement  |     Status:  assigned
  Priority:  Normal       |  Milestone:  MacPorts 2.6.0
 Component:  base         |    Version:
Resolution:               |   Keywords:
      Port:               |
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Comment (by raimue):

 Replying to [comment:21 mojca]:
 > I would really like to see the ability to proliferate this information
 from PortGroups or potentially even dependencies. If one port depends on
 `qt5` which cannot be compiled on older systems, then this port (or any
 other dependent port of `qt5`) should have those darwin versions
 blacklisted as well.

 I agree the platform information should be used early in a `port install`
 and error out before even installing dependencies. But in my opinion, this
 is out of scope of defining a syntax for `platforms`.

 I am still not convinced of the `-blacklist`/`-whitelist` approach. What
 if I only specify a whitelist? Would it imply all other versions are not
 supported?

 Also, consider this example:

 {{{
 platforms-blacklist {darwin >= 10}
 platforms-whitelist {darwin 11}
 }}}

 Of course this is an artificial example, but the syntax supports it. You
 said start with whitelist, then apply blacklist. So, the blacklist
 overrides `{darwin 11}` in the whitelist and it is not supported? Or is
 `{darwin 11}` supported although it is matched by the blacklist?
 Implementing and documenting this behavior seems complicated and overly
 complex.

 With a `platforms` option taking entries for supported platforms as
 [#comment:20 as proposed above], there is no room for ambiguity:

 {{{
 platforms {darwin < 10} {darwin 11}
 }}}

-- 
Ticket URL: <https://trac.macports.org/ticket/15712#comment:23>
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