Add DEPENDS option to qt5_wrap_cpp()

Currently the moc rule does not support dependency scanning, so after
successful moc file generation it will ignore implicit dependencies
in the header file.

Although this works in most typical scenarios, at least in one case
incremental builds become broken: when using Q_PLUGIN_METADATA() with
the FILE argument.

If FILE refers to a JSON file and latter was updated, then the expected
behavior is to regenerate the moc file. Since CMake add_custom_command()
does not support late dependency setup, all dependencies should be
explicitly listed in a DEPENDS section.

This patch adds the DEPENDS multiarg option to qt5_wrap_cpp(),
allowing to specify additional dependencies to the moc rule.

Task-number: QTBUG-44009
Change-Id: I2052ce23d3cb0c87c6bd99fcb7e8a71a7be9a330
Reviewed-by: Kevin Funk <kevin.funk@kdab.com>
Reviewed-by: Olivier Goffart (Woboq GmbH) <ogoffart@woboq.com>
Reviewed-by: Daniel Levin <dendy.ua@gmail.com>

1 files changed, 6 insertions, 5 deletions

diff --git a/src/corelib/Qt5CoreMacros.cmake b/src/corelib/Qt5CoreMacros.cmake
index 18563764ad..c441d3ad73 100644
--- a/src/corelib/Qt5CoreMacros.cmake
+++ b/src/corelib/Qt5CoreMacros.cmake
@@ -94,7 +94,7 @@ endmacro()
 
 
 # helper macro to set up a moc rule
-macro(QT5_CREATE_MOC_COMMAND infile outfile moc_flags moc_options moc_target)
+macro(QT5_CREATE_MOC_COMMAND infile outfile moc_flags moc_options moc_target moc_depends)
     # Pass the parameters in a file.  Set the working directory to
     # be that containing the parameters file and reference it by
     # just the file name.  This is necessary because the moc tool on
@@ -131,7 +131,7 @@ macro(QT5_CREATE_MOC_COMMAND infile outfile moc_flags moc_options moc_target)
     set(_moc_extra_parameters_file @${_moc_parameters_file})
     add_custom_command(OUTPUT ${outfile}
                        COMMAND ${Qt5Core_MOC_EXECUTABLE} ${_moc_extra_parameters_file}
-                       DEPENDS ${infile}
+                       DEPENDS ${infile} ${moc_depends}
                        ${_moc_working_dir}
                        VERBATIM)
 endmacro()
@@ -151,7 +151,7 @@ function(QT5_GENERATE_MOC infile outfile )
         endif()
         set(moc_target ${ARGV3})
     endif()
-    qt5_create_moc_command(${abs_infile} ${_outfile} "${moc_flags}" "" "${moc_target}")
+    qt5_create_moc_command(${abs_infile} ${_outfile} "${moc_flags}" "" "${moc_target}" "")
     set_source_files_properties(${outfile} PROPERTIES SKIP_AUTOMOC TRUE)  # dont run automoc on this file
 endfunction()
 
@@ -164,13 +164,14 @@ function(QT5_WRAP_CPP outfiles )
 
     set(options)
     set(oneValueArgs TARGET)
-    set(multiValueArgs OPTIONS)
+    set(multiValueArgs OPTIONS DEPENDS)
 
     cmake_parse_arguments(_WRAP_CPP "${options}" "${oneValueArgs}" "${multiValueArgs}" ${ARGN})
 
     set(moc_files ${_WRAP_CPP_UNPARSED_ARGUMENTS})
     set(moc_options ${_WRAP_CPP_OPTIONS})
     set(moc_target ${_WRAP_CPP_TARGET})
+    set(moc_depends ${_WRAP_CPP_DEPENDS})
 
     if (moc_target AND CMAKE_VERSION VERSION_LESS 2.8.12)
         message(FATAL_ERROR "The TARGET parameter to qt5_wrap_cpp is only available when using CMake 2.8.12 or later.")
@@ -178,7 +179,7 @@ function(QT5_WRAP_CPP outfiles )
     foreach(it ${moc_files})
         get_filename_component(it ${it} ABSOLUTE)
         qt5_make_output_file(${it} moc_ cpp outfile)
-        qt5_create_moc_command(${it} ${outfile} "${moc_flags}" "${moc_options}" "${moc_target}")
+        qt5_create_moc_command(${it} ${outfile} "${moc_flags}" "${moc_options}" "${moc_target}" "${moc_depends}")
         list(APPEND ${outfiles} ${outfile})
     endforeach()
     set(${outfiles} ${${outfiles}} PARENT_SCOPE)