[MacPorts] #56411: opencv @3.4.1_2+contrib fails to build with protobuf-cpp (was: opencv @3.4.1_2 +python27 fails to build on 10.13.4 HighSierra)

[MacPorts]

#56411: opencv @3.4.1_2+contrib fails to build with protobuf-cpp
------------------------+----------------------
  Reporter:  duchowski  |      Owner:  stromnov
      Type:  defect     |     Status:  assigned
  Priority:  Normal     |  Milestone:
 Component:  ports      |    Version:  2.4.3
Resolution:             |   Keywords:
      Port:  opencv     |
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Changes (by ryandesign):

 * cc: meghadri (added)


Comment:

 The +contrib variant is the one that uses protobuf, not the +python*
 variants.

 The suggested patch is not correct, in that the use of a `path:`-style
 dependency is not correct, because that allows either protobuf-cpp or
 protobuf3-cpp to satisfy the dependency (whichever is already installed).
 If only protobuf3-cpp will work, then that is what the port should depend
 on.

 Has duplicate #56634.

 See also #56135 for the overall effort to move all ports from protobuf 2
 to protobuf 3.

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Ticket URL: <https://trac.macports.org/ticket/56411#comment:8>
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