[MacPorts] #60566: Setting known_fail yes should prevent the port from being installed

[MacPorts]

#60566: Setting known_fail yes should prevent the port from being installed
-------------------------+-----------------------------
 Reporter:  ryandesign   |      Owner:  (none)
     Type:  enhancement  |     Status:  new
 Priority:  Normal       |  Milestone:  MacPorts Future
Component:  base         |    Version:  2.6.2
 Keywords:               |       Port:
-------------------------+-----------------------------
 Some ports do this (this is from go):

 {{{
 if {${os.platform} eq "darwin" && ${os.major} < 11} {
     known_fail yes
     pre-fetch {
         ui_error "${name} @${version} requires OS X 10.7 or greater."
         return -code error "incompatible Mac OS X version"
     }
 }
 }}}

 In other words in addition to setting `known_fail yes` it prints an error
 message in a `pre-fetch` block to prevent the port from being installed.

 It would be great if MacPorts base itself would ensure that the port
 cannot be installed when `known_fail yes` is set.

 Ports still need an opportunity to specify a reason why they would fail.
 Maybe a new option could be created for that, so that a portfile could
 then say:

 {{{
 # hypothetical code
 if {${os.platform} eq "darwin" && ${os.major} < 11} {
     known_fail yes
     known_fail_reason requires OS X 10.7 or greater
 }
 }}}

 Maybe implementing this would make other smaller enhancements to
 `known_fail yes` like #60564 and #60565 unnecessary.

-- 
Ticket URL: <https://trac.macports.org/ticket/60566>
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