nepomuk-widgets fails to build on High Sierra: :info:build Undefined symbols for architecture x86_64:

[Polyergic (Shad Sterling)]

Reinstalling all ports after upgrading to High Sierra, a few are failing to build, including nepomuk-widgets:

:info:build /usr/bin/clang++  -pipe -Os -stdlib=libc++ -fno-common -Wnon-virtual-dtor -Wno-long-long -Wundef -Wcast-align -Wchar-subscripts -Wall -W -Wpointer-arith -Wformat-security -Woverloaded-virtual -fno-common -fvisibility=hidden -Werror=return-type -fvisibility-inlines-hidden -Wno-return-type-c-linkage -O2 -DNDEBUG -DQT_NO_DEBUG -arch x86_64 -mmacosx-version-min=10.13 -Wl,-search_paths_first -Wl,-headerpad_max_install_names -Wl,-headerpad_max_install_names CMakeFiles/tagwidgetapp.dir/tagwidgetapp_automoc.cpp.o CMakeFiles/tagwidgetapp.dir/tagwidgetapp.cpp.o CMakeFiles/tagwidgetapp.dir/tagwidgettest.cpp.o  -o tagwidgetapp.app/Contents/MacOS/tagwidgetapp -Wl,-rpath,/opt/local/lib ../lib/libnepomukwidgets.4.14.3.dylib /opt/local/lib/libkio.5.14.3.dylib /opt/local/libexec/qt4/lib/libQtNetwork.dylib /opt/local/libexec/qt4/lib/libQtXml.dylib /opt/local/lib/libnepomukcore.4.14.3.dylib /opt/local/lib/libkdeui.5.14.3.dylib /opt/local/libexec/qt4/lib/libQtGui.dylib /opt/local/libexec/qt4/lib/libQtSvg.dylib /opt/local/lib/libkdecore.5.14.3.dylib /opt/local/libexec/qt4/lib/libQtDBus.dylib /opt/local/libexec/qt4/lib/libQtCore.dylib -framework Carbon /opt/local/lib/libsoprano.dylib 
:info:build Undefined symbols for architecture x86_64:
:info:build   "Nepomuk2::FileMetaDataWidget::setItems(KFileItemList const&)", referenced from:
:info:build       FileMetadataWidgetTest::slotChooseFiles() in metadatawidgettest.cpp.o
:info:build   "Nepomuk2::FileMetaDataWidget::FileMetaDataWidget(QWidget*)", referenced from:
:info:build       FileMetadataWidgetTest::FileMetadataWidgetTest(QWidget*, QFlags<Qt::WindowType>) in metadatawidgettest.cpp.o
:info:build ld: symbol(s) not found for architecture x86_64
:info:build clang: error: Undefined symbols for architecture x86_64:
:info:build   "Nepomuk2::TagWidget::setAlignment(QFlags<Qt::AlignmentFlag>)", referenced from:
:info:build       TagWidgetTest::alignRight(bool) in tagwidgettest.cpp.o
:info:build       TagWidgetTest::qt_static_metacall(QObject*, QMetaObject::Call, int, void**) in tagwidgettest.cpp.o
:info:build   "Nepomuk2::TagWidget::setModeFlags(QFlags<Nepomuk2::TagWidget::ModeFlag>)", referenced from:
:info:build       TagWidgetTest::enableMinimode(bool) in tagwidgettest.cpp.o
:info:build       TagWidgetTest::disableClicking(bool) in tagwidgettest.cpp.o
:info:build       TagWidgetTest::setReadOnly(bool) in tagwidgettest.cpp.o
:info:build       TagWidgetTest::qt_static_metacall(QObject*, QMetaObject::Call, int, void**) in tagwidgettest.cpp.o
:info:build   "Nepomuk2::TagWidget::setMaxTagsShown(int)", referenced from:
:info:build       TagWidgetTest::TagWidgetTest() in tagwidgettest.cpp.o
:info:build   "Nepomuk2::TagWidget::TagWidget(QWidget*)", referenced from:
:info:build       TagWidgetTest::TagWidgetTest() in tagwidgettest.cpp.o
:info:build   "Nepomuk2::TagWidget::modeFlags() const", referenced from:
:info:build       TagWidgetTest::enableMinimode(bool) in tagwidgettest.cpp.o
:info:build       TagWidgetTest::disableClicking(bool) in tagwidgettest.cpp.o
:info:build       TagWidgetTest::setReadOnly(bool) in tagwidgettest.cpp.o
:info:build       TagWidgetTest::qt_static_metacall(QObject*, QMetaObject::Call, int, void**) in tagwidgettest.cpp.o
:info:build ld: symbol(s) not found for architecture x86_64
:info:build linker command failed with exit code 1 (use -v to see invocation)
:info:build Undefined symbols for architecture x86_64:
:info:build   "Nepomuk2::FileMetaDataConfigWidget::setItems(KFileItemList const&)", referenced from:
:info:build       FileMetadataWidgetTest::slotChooseFiles() in metadataconfigwidgetapp.cpp.o
:info:build   "Nepomuk2::FileMetaDataConfigWidget::FileMetaDataConfigWidget(QWidget*)", referenced from:
:info:build       FileMetadataWidgetTest::FileMetadataWidgetTest(QWidget*, QFlags<Qt::WindowType>) in metadataconfigwidgetapp.cpp.o
:info:build ld: symbol(s) not found for architecture x86_64
:info:build clang: error: linker command failed with exit code 1 (use -v to see invocation)

[NicosPavlov]

It appears this was a similar problem as #55046 about symbols visibility. Should be fixed with following commit.

[NicosPavlov]

In 27fa77cd502ed7c083c5866721fc5ef3e30d33f6/macports-ports:

nepomuk-widgets: fix symbols visibility (fix: #55161)