Fix cases of output variables not being passed back to calling scope

Some versionless wrappers were not passing back output variables to
their calling scope. Ensure they always are.

Fix qt6_extract_metatypes() to set its output variable in the parent
scope (it was previously setting it erroneously in the local scope).

Some functions had code paths that would not set output variables.
This would allow situations where if the variables had an initial
value set by a higher up parent scope, the output variable would
still have that value in the caller's scope upon return. That could be
misleading, so fix these code paths to explicitly set the output
variable to an empty string instead.

Task-number: QTBUG-96121
Task-number: QTBUG-96219
Pick-to: 6.2
Change-Id: I291775813f025cabdccd4372ac077cdfd3ec090e
Reviewed-by: Joerg Bornemann <joerg.bornemann@qt.io>

src/corelib/Qt6CoreMacros.cmake

@@ -355,7 +355,12 @@ if(NOT QT_NO_CREATE_VERSIONLESS_FUNCTIONS)
         elseif(QT_DEFAULT_MAJOR_VERSION EQUAL 6)
             qt6_add_resources("${outfiles}" ${ARGN})
         endif()
-        if(NOT TARGET ${outfiles})
+        if(TARGET ${outfiles})
+            cmake_parse_arguments(PARSE_ARGV 1 arg "" "OUTPUT_TARGETS" "")
+            if (arg_OUTPUT_TARGETS)
+                set(${arg_OUTPUT_TARGETS} ${${arg_OUTPUT_TARGETS}} PARENT_SCOPE)
+            endif()
+        else()
             set("${outfiles}" "${${outfiles}}" PARENT_SCOPE)
         endif()
     endfunction()
@@ -667,6 +672,8 @@ function(_qt_internal_find_ios_development_team_id out_var)
         string(STRIP "${team_id}" team_id)
         set_property(GLOBAL PROPERTY _qt_internal_ios_development_team_id "${team_id}")
         set("${out_var}" "${team_id}" PARENT_SCOPE)
+    else()
+        set("${out_var}" "" PARENT_SCOPE)
     endif()
 endfunction()
 
@@ -704,6 +711,8 @@ function(_qt_internal_get_ios_bundle_identifier_prefix out_var)
     if(prefix AND NOT prefix_error)
         set_property(GLOBAL PROPERTY _qt_internal_ios_bundle_identifier_prefix "${prefix}")
         set("${out_var}" "${prefix}" PARENT_SCOPE)
+    else()
+        set("${out_var}" "" PARENT_SCOPE)
     endif()
 endfunction()
 
@@ -1195,7 +1204,7 @@ function(qt6_extract_metatypes target)
     target_sources(${target} INTERFACE ${metatypes_file_genex_build})
 
     if(arg_OUTPUT_FILES)
-        set(${arg_OUTPUT_FILES} "${metatypes_file}")
+        set(${arg_OUTPUT_FILES} "${metatypes_file}" PARENT_SCOPE)
     endif()
 
     # Chech whether the generated json file needs to be installed.
@@ -1234,6 +1243,10 @@ endfunction()
 if(NOT QT_NO_CREATE_VERSIONLESS_FUNCTIONS)
     function(qt_extract_metatypes)
         qt6_extract_metatypes(${ARGV})
+        cmake_parse_arguments(PARSE_ARGV 0 arg "" "OUTPUT_FILES" "")
+        if(arg_OUTPUT_FILES)
+            set(${arg_OUTPUT_FILES} "${${arg_OUTPUT_FILES}}" PARENT_SCOPE)
+        endif()
     endfunction()
 endif()
 
@@ -1816,6 +1829,9 @@ function(_qt_internal_process_resource target resourceName)
     if(isBinary)
         # Add generated .rcc target to 'all' set
         add_custom_target(binary_resource_${generatedBaseName} ALL DEPENDS "${generatedOutfile}")
+        if(rcc_OUTPUT_TARGETS)
+            set(${rcc_OUTPUT_TARGETS} "" PARENT_SCOPE)
+        endif()
     else()
         set_property(SOURCE "${generatedOutfile}" PROPERTY SKIP_AUTOGEN ON)
         set_property(TARGET ${target} APPEND PROPERTY _qt_generated_qrc_files "${generatedResourceFile}")
@@ -1971,6 +1987,10 @@ function(qt6_add_plugin target)
         if(NOT arg___QT_INTERNAL_NO_PROPAGATE_PLUGIN_INITIALIZER)
             __qt_internal_propagate_object_library("${target}" "${plugin_init_target}")
         endif()
+    else()
+        if(arg_OUTPUT_TARGETS)
+            set(${arg_OUTPUT_TARGETS} "" PARENT_SCOPE)
+        endif()
     endif()
 
     target_compile_definitions(${target} PRIVATE
@@ -1982,6 +2002,10 @@ endfunction()
 if(NOT QT_NO_CREATE_VERSIONLESS_FUNCTIONS)
     function(qt_add_plugin)
         qt6_add_plugin(${ARGV})
+        cmake_parse_arguments(PARSE_ARGV 1 arg "" "OUTPUT_TARGETS" "")
+        if(arg_OUTPUT_TARGETS)
+            set(${arg_OUTPUT_TARGETS} ${${arg_OUTPUT_TARGETS}} PARENT_SCOPE)
+        endif()
     endfunction()
 endif()