[MacPorts] #54861: mlt-qt5 install fails with the message "Package Qt5Core was not found in the pkg-config search path."

[MacPorts]

#54861: mlt-qt5 install fails with the message "Package Qt5Core was not found in
the pkg-config search path."
--------------------------+----------------------
  Reporter:  wilya7       |      Owner:  ddennedy
      Type:  defect       |     Status:  assigned
  Priority:  Normal       |  Milestone:
 Component:  ports        |    Version:
Resolution:               |   Keywords:
      Port:  mlt mlt-qt5  |
--------------------------+----------------------

Comment (by RJVB):

 Congratulations, you found a bug ...

 I overlooked the fact that dependency version checking is a bit of a hack.
 This is what the port should have done:

 {{{
 diff --git a/multimedia/mlt/Portfile b/multimedia/mlt/Portfile
 --- a/multimedia/mlt/Portfile
 +++ b/multimedia/mlt/Portfile
 @@ -42,7 +42,7 @@ if {${subport} eq "${name}"} {
      if {[info procs qt5.active_version] eq ""} {
          proc qt5.active_version {} {
              global prefix
 -            if {[file exists ${prefix}/bin/pkg-config]} {
 +            if {[file exists ${prefix}/bin/pkg-config/Qt5Core.pc]} {
                  set av [exec ${prefix}/bin/pkg-config --modversion
 Qt5Core]
                  return ${av}
              } else {
 @@ -53,10 +53,15 @@ if {${subport} eq "${name}"} {

      qt5.depends_component \
                      qtsvg
 -    if {[vercmp [qt5.active_version] 5.7.0] >= 0} {
 -        configure.cxxflags-append \
 -                    -stdlib=libc++ \
 -                    -std=c++11
 +    pre-configure {
 +        # qt5.active_version only works if Qt is installed; we can
 +        # be certain that is the case in the pre-configure phase.
 +        if {[vercmp [qt5.active_version] 5.7.0] >= 0} {
 +            ui_info "Qt 5.7.0 and up require at least C++11"
 +            configure.cxxflags-append \
 +                        -stdlib=libc++ \
 +                        -std=c++11
 +        }
      }
  }

 }}}

 You already uninstalled Qt5-qtbase, maybe you can apply the patch and
 confirm if installing mlt-qt5 now indeed pulls in qt5-qtbase as I think it
 will?

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Ticket URL: <https://trac.macports.org/ticket/54861#comment:5>
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