How to run QT's `lupdate`-tool with a `qmake CONFIG`?

This question has been posted before in the qt community: https://forum.qt.io/topic/106930/how-to-run-lupdate-with-a-qmake-config

I use such a construct in my project files:

LANGUAGES = de
TRANSLATION_NAME = authorization
include(../../gen_translations.pri)

where gen_translations.pri looks like so:

# parameters: var, prepend, append
defineReplace(prependAll) {
 for(a,$$1):result += $$2$${a}$$3
 return($$result)
}

TRANSLATIONS = $$prependAll(LANGUAGES, $$PWD/libs/$$TRANSLATION_NAME/translations/lib$${TRANSLATION_NAME}_, .ts)

TRANSLATIONS_FILES =

qtPrepareTool(LRELEASE, lrelease)

for(tsfile, TRANSLATIONS) {
 qmfile = $$shadowed($$tsfile)
 qmfile ~= s,.ts$,.qm,
 qmdir = $$dirname(qmfile)
 !exists($$qmdir) {
 mkpath($$qmdir)|error("Aborting.")
 }
 command = $$LRELEASE -removeidentical $$tsfile -qm $$qmfile
 system($$command)|error("Failed to run: $$command")
 TRANSLATIONS_FILES += $$qmfile
}

for(qmentry, $$list($$TRANSLATIONS_FILES)) {
  qmpath = $$OUT_PWD/../translations
  qmpathname = $$replace(qmpath,/,)
  qmpathname = $$replace(qmpathname,\.,)
  qmpathname = $$replace(qmpathname,:,)
  qmpathname = $$replace(qmpathname," ",)
  qmentity = qmfiles_$${qmpathname}
  eval($${qmentity}.files += $$qmentry)
  eval($${qmentity}.path = $$qmpath)
  INSTALLS *= $${qmentity}
}

It generates the *.qm files for me and moves them to a defined location with make install.

I do not want qmake to execute that whole stuff for each build on my developing machine. Therefore I want to make it conditional by wrapping it for qmake:

translate{
LANGUAGES = de
TRANSLATION_NAME = authorization
include(../../gen_translations.pri)
}

That way I can decide when I want to get *.qm files and when not. But then I am unable to run lupdate on the project file beforehand because it is blocked by that conditional.

I am sure, that someone has a better idea to accomplish the task.

Thanks in advance.

I'm sharing here my recipe for the vmpk project. I've borrowed it from the Arora project (I think). It is much simpler than yours, and I let qmake to decide if it is necessary regenerate any .qm files when the output has been erased or the input .ts has changed, like any other compiler does.

updateqm.pri

# update translations

isEmpty(QMAKE_LRELEASE) {
    win32:QMAKE_LRELEASE = $$[QT_INSTALL_BINS]\\lrelease.exe
    else:QMAKE_LRELEASE = $$[QT_INSTALL_BINS]/lrelease
    !exists($$QMAKE_LRELEASE) { QMAKE_LRELEASE = lrelease }
}

updateqm.input = TRANSLATIONS
updateqm.output = $$OUT_PWD/${QMAKE_FILE_BASE}.qm
updateqm.commands = $$QMAKE_LRELEASE ${QMAKE_FILE_IN} -qm $$OUT_PWD/${QMAKE_FILE_BASE}.qm
updateqm.CONFIG += no_link target_predeps
QMAKE_EXTRA_COMPILERS += updateqm

project.pro:

TRANSLATIONS +=  \
    translations/project_en.ts \
    translations/project_cs.ts \
    translations/project_de.ts \
    translations/project_es.ts \
    translations/project_fr.ts \
    translations/project_ru.ts 

include(updateqm.pri)

With this project file you can do, as always:

lupdate project.pro

Anyway, Qt5 has a builtin CONFIG+=lrelease option that makes "updateqm.pri" deprecated.