Revert "Revert "CMake: Add facility to mark package dependencies as optional""

This reverts commit b0c51f86f40b6b6d18fe2bb75cc851d36395240d.
The build failure caused by 58c1c6ee5c986d502b56eb1cc57f1d9444d42031 has
been fixed.

Change-Id: Ic7458d54c7a874588e8b1bfeca61df1842763656
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>

5 files changed, 44 insertions, 17 deletions

diff --git a/cmake/QtConfigDependencies.cmake.in b/cmake/QtConfigDependencies.cmake.in
index 3792e9394e..52d6421b5e 100644
--- a/cmake/QtConfigDependencies.cmake.in
+++ b/cmake/QtConfigDependencies.cmake.in
@@ -1,14 +1,15 @@
 set(@INSTALL_CMAKE_NAMESPACE@_DEPENDENCIES_FOUND FALSE)
 
-# note: _third_party_deps example: "ICU\\;1.0\\;i18n uc data;ZLIB\\;\\;"
+# note: _third_party_deps example: "ICU\\;FALSE\\;1.0\\;i18n uc data;ZLIB\\;FALSE\\;\\;"
 set(_third_party_deps "@third_party_deps@")
 
 @third_party_extra@
 
 foreach(_target_dep ${_third_party_deps})
     list(GET _target_dep 0 pkg)
-    list(GET _target_dep 1 version)
-    list(GET _target_dep 2 components)
+    list(GET _target_dep 1 is_optional)
+    list(GET _target_dep 2 version)
+    list(GET _target_dep 3 components)
     set(find_package_args "${pkg}")
     if(version)
         list(APPEND find_package_args "${version}")
@@ -29,7 +30,14 @@ foreach(_target_dep ${_third_party_deps})
     set(@INSTALL_CMAKE_NAMESPACE@_DEPENDENCY_NOT_FOUND_MESSAGE
         "${__@INSTALL_CMAKE_NAMESPACE@_message}")
 
-    find_dependency(${find_package_args})
+    if(is_optional)
+        if(${CMAKE_FIND_PACKAGE_NAME}_FIND_QUIETLY)
+            list(APPEND find_package_args QUIET)
+        endif()
+        find_package(${find_package_args})
+    else()
+        find_dependency(${find_package_args})
+    endif()
 endforeach()
 
 set(@INSTALL_CMAKE_NAMESPACE@_DEPENDENCIES_FOUND TRUE)
diff --git a/cmake/QtFindPackageHelpers.cmake b/cmake/QtFindPackageHelpers.cmake
index 0ca585d1d4..c68ba4d14a 100644
--- a/cmake/QtFindPackageHelpers.cmake
+++ b/cmake/QtFindPackageHelpers.cmake
@@ -15,7 +15,8 @@ endfunction()
 
 macro(qt_find_package)
     # Get the target names we expect to be provided by the package.
-    set(options CONFIG NO_MODULE MODULE REQUIRED)
+    set(find_package_options CONFIG NO_MODULE MODULE REQUIRED)
+    set(options ${find_package_options} MARK_OPTIONAL)
     set(oneValueArgs MODULE_NAME QMAKE_LIB)
     set(multiValueArgs PROVIDED_TARGETS COMPONENTS)
     cmake_parse_arguments(arg "${options}" "${oneValueArgs}" "${multiValueArgs}" ${ARGN})
@@ -90,7 +91,7 @@ macro(qt_find_package)
     endif()
 
     # Ensure the options are back in the original unparsed arguments
-    foreach(opt IN LISTS options)
+    foreach(opt IN LISTS find_package_options)
         if(arg_${opt})
             list(APPEND arg_UNPARSED_ARGUMENTS ${opt})
         endif()
@@ -129,8 +130,9 @@ macro(qt_find_package)
                     set(qt_find_package_target_name ${aliased_target})
                 endif()
 
-                set_target_properties(${qt_find_package_target_name}
-                                      PROPERTIES INTERFACE_QT_PACKAGE_NAME ${ARGV0})
+                set_target_properties(${qt_find_package_target_name} PROPERTIES
+                    INTERFACE_QT_PACKAGE_NAME ${ARGV0}
+                    INTERFACE_QT_PACKAGE_IS_OPTIONAL ${arg_MARK_OPTIONAL})
                 if(package_version)
                     set_target_properties(${qt_find_package_target_name}
                                           PROPERTIES INTERFACE_QT_PACKAGE_VERSION ${ARGV1})
diff --git a/cmake/QtModuleDependencies.cmake.in b/cmake/QtModuleDependencies.cmake.in
index 3d19fac784..24d132b57d 100644
--- a/cmake/QtModuleDependencies.cmake.in
+++ b/cmake/QtModuleDependencies.cmake.in
@@ -4,13 +4,14 @@ find_dependency(@INSTALL_CMAKE_NAMESPACE@ @PROJECT_VERSION@
     PATHS "${CMAKE_CURRENT_LIST_DIR}/.." ${QT_EXAMPLES_CMAKE_PREFIX_PATH} NO_DEFAULT_PATH
 )
 
-# note: _third_party_deps example: "ICU\\;1.0\\;i18n uc data;ZLIB\\;\\;"
+# note: _third_party_deps example: "ICU\\;FALSE\\;1.0\\;i18n uc data;ZLIB\\;FALSE\\;\\;"
 set(_third_party_deps "@third_party_deps@")
 
 foreach(_target_dep ${_third_party_deps})
     list(GET _target_dep 0 pkg)
-    list(GET _target_dep 1 version)
-    list(GET _target_dep 2 components)
+    list(GET _target_dep 1 is_optional)
+    list(GET _target_dep 2 version)
+    list(GET _target_dep 3 components)
     set(find_package_args "${pkg}")
     if(version)
         list(APPEND find_package_args "${version}")
@@ -20,7 +21,14 @@ foreach(_target_dep ${_third_party_deps})
         list(APPEND find_package_args COMPONENTS ${components})
     endif()
 
-    find_dependency(${find_package_args})
+    if(is_optional)
+        if(${CMAKE_FIND_PACKAGE_NAME}_FIND_QUIETLY)
+            list(APPEND find_package_args QUIET)
+        endif()
+        find_package(${find_package_args})
+    else()
+        find_dependency(${find_package_args})
+    endif()
 endforeach()
 
 # Find Qt tool package.
diff --git a/cmake/QtPluginDependencies.cmake.in b/cmake/QtPluginDependencies.cmake.in
index bae6d85c7b..9d16bedeba 100644
--- a/cmake/QtPluginDependencies.cmake.in
+++ b/cmake/QtPluginDependencies.cmake.in
@@ -1,12 +1,13 @@
 set(@target@_FOUND FALSE)
 
-# note: _third_party_deps example: "ICU\\;1.0\\;i18n uc data;ZLIB\\;\\;"
+# note: _third_party_deps example: "ICU\\;FALSE\\;1.0\\;i18n uc data;ZLIB\\;FALSE\\;\\;"
 set(_third_party_deps "@third_party_deps@")
 
 foreach(_target_dep ${_third_party_deps})
     list(GET _target_dep 0 pkg)
-    list(GET _target_dep 1 version)
-    list(GET _target_dep 2 components)
+    list(GET _target_dep 1 is_optional)
+    list(GET _target_dep 2 version)
+    list(GET _target_dep 3 components)
     set(find_package_args "${pkg}")
     if(version)
         list(APPEND find_package_args "${version}")
@@ -16,7 +17,14 @@ foreach(_target_dep ${_third_party_deps})
         list(APPEND find_package_args COMPONENTS ${components})
     endif()
 
-    find_dependency(${find_package_args})
+    if(is_optional)
+        if(${CMAKE_FIND_PACKAGE_NAME}_FIND_QUIETLY)
+            list(APPEND find_package_args QUIET)
+        endif()
+        find_package(${find_package_args})
+    else()
+        find_dependency(${find_package_args})
+    endif()
 endforeach()
 
 # note: target_deps example: "Qt6Core\;5.12.0;Qt6Gui\;5.12.0"
diff --git a/cmake/QtPostProcessHelpers.cmake b/cmake/QtPostProcessHelpers.cmake
index 0da6d9e4c3..56b2d5e56f 100644
--- a/cmake/QtPostProcessHelpers.cmake
+++ b/cmake/QtPostProcessHelpers.cmake
@@ -43,6 +43,7 @@ macro(qt_collect_third_party_deps target)
             get_target_property(package_name ${dep} INTERFACE_QT_PACKAGE_NAME)
             if(dep_seen EQUAL -1 AND package_name)
                 list(APPEND third_party_deps_seen ${dep})
+                get_target_property(package_is_optional ${dep} INTERFACE_QT_PACKAGE_IS_OPTIONAL)
                 get_target_property(package_version ${dep} INTERFACE_QT_PACKAGE_VERSION)
                 if(NOT package_version)
                     set(package_version "")
@@ -54,7 +55,7 @@ macro(qt_collect_third_party_deps target)
                 endif()
 
                 list(APPEND third_party_deps
-                            "${package_name}\;${package_version}\;${package_components}")
+                    "${package_name}\;${package_is_optional}\;${package_version}\;${package_components}")
             endif()
         endif()
     endforeach()