CMake: Don't install metatypes files for user projects

Installing extracted metatypes json files for user projects was an
oversight. We shouldn't install anything on behalf of user projects,
but rather give them enough information so they can do it the
themselves.

Make all the install options of qt6_extract_metatypes internal,
change the behavior not to install the files by default, unless
__QT_INTERNAL_INSTALL is passed, which is used for the Qt build only.

__QT_INTERNAL_NO_INSTALL is now a no-op and should be removed from
projects.

This is behavior change for existing public API, but it's better to
fix this now before 6.2.0 release.

Introduce a new OUTPUT_FILES option to allow assigning the extracted
metatype file paths into a variable that the project provides.
The project can then install the files where they need them.

[ChangeLog][CMake] qt6_extract_metatypes does not install metatypes
files anymore. Instead the OUTPUT_FILES option can be provided to get
the list of extracted files for further processing.

Pick-to: 6.2
Task-number: QTBUG-95845
Change-Id: If5dd0255a5fea2b598e15118c29ec2ab2ba4324e
Reviewed-by: Alexey Edelev <alexey.edelev@qt.io>
Reviewed-by: Qt CI Bot <qt_ci_bot@qt-project.org>
Reviewed-by: Fabian Kosmale <fabian.kosmale@qt.io>

cmake/QtModuleHelpers.cmake

@@ -596,12 +596,11 @@ set(QT_LIBINFIX \"${QT_LIBINFIX}\")")
     endif()
     if (NOT ${arg_NO_GENERATE_METATYPES})
         if (NOT target_type STREQUAL "INTERFACE_LIBRARY")
-            set(metatypes_install_dir ${INSTALL_LIBDIR}/metatypes)
-            set(args)
-            if (NOT QT_WILL_INSTALL)
-                set(args __QT_INTERNAL_NO_INSTALL)
-            else()
-                set(args INSTALL_DIR "${metatypes_install_dir}")
+            set(args "")
+            if(QT_WILL_INSTALL)
+                set(metatypes_install_dir "${INSTALL_LIBDIR}/metatypes")
+                list(APPEND args
+                    __QT_INTERNAL_INSTALL __QT_INTERNAL_INSTALL_DIR "${metatypes_install_dir}")
             endif()
             qt6_extract_metatypes(${target} ${args})
         elseif(${arg_GENERATE_METATYPES})

src/corelib/CMakeLists.txt

@@ -318,11 +318,10 @@ set_source_files_properties(${qobject_moc_files} PROPERTIES HEADER_FILE_ONLY ON)
 
 set(core_metatype_args MANUAL_MOC_JSON_FILES ${core_qobject_metatypes_json_list})
 
-set(metatypes_install_dir ${INSTALL_LIBDIR}/metatypes)
-if (NOT QT_WILL_INSTALL)
-    list(APPEND core_metatype_args __QT_INTERNAL_NO_INSTALL)
-else()
-    list(APPEND core_metatype_args INSTALL_DIR "${metatypes_install_dir}")
+if(QT_WILL_INSTALL)
+    set(metatypes_install_dir ${INSTALL_LIBDIR}/metatypes)
+    list(APPEND core_metatype_args
+        __QT_INTERNAL_INSTALL __QT_INTERNAL_INSTALL_DIR "${metatypes_install_dir}")
 endif()
 # Use qt6_extract_metatypes instead of GENERATE_METATYPES so that we can manually pass the
 # additional json files.

src/corelib/Qt6CoreMacros.cmake

@@ -957,16 +957,25 @@ if(NOT QT_NO_CREATE_VERSIONLESS_FUNCTIONS)
 endif()
 
 # Extracts metatypes from a Qt target and generates a metatypes.json for it.
+#
 # By default we check whether AUTOMOC has been enabled and we extract the information from the
 # target's AUTOMOC supporting files.
-# Should you not wish to use automoc you need to pass in all the generated json files via the
+#
+# Should you not wish to use AUTOMOC you need to pass in all the generated json files via the
 # MANUAL_MOC_JSON_FILES parameter. The latter can be obtained by running moc with
 # the --output-json parameter.
 # Params:
-#   INSTALL_DIR: Location where to install the metatypes file. For public consumption,
-#                defaults to a ${CMAKE_INSTALL_PREFIX}/${INSTALL_LIBDIR}/metatypes directory.
-#                Executable metatypes files are never installed.
+#   OUTPUT_FILES: a variable name in which to store the list of the extracted metatype json files.
+#                 A typical use case would to install them.
+#
+#   TODO: Move these internal options out into an internal function to be used by Qt only.
+#   __QT_INTERNAL_INSTALL_DIR: Location where to install the metatypes file. For public consumption,
+#                              defaults to a ${CMAKE_INSTALL_PREFIX}/${INSTALL_LIBDIR}/metatypes
+#                              directory.
+#                              Executable metatypes files are never installed.
 #   __QT_INTERNAL_NO_INSTALL: When passed, will skip installation of the metatype file.
+#   __QT_INTERNAL_INSTALL: Installs the metatypes files into the default Qt metatypes folder.
+#                          Only to be used by the Qt build.
 function(qt6_extract_metatypes target)
 
     get_target_property(existing_meta_types_file ${target} INTERFACE_QT_META_TYPES_BUILD_FILE)
@@ -974,8 +983,27 @@ function(qt6_extract_metatypes target)
         return()
     endif()
 
+    set(args_option
+        # TODO: Remove this once all leaf module usages of it are removed. It's now a no-op.
+        __QT_INTERNAL_NO_INSTALL
+
+        # TODO: Move this into a separate internal function, so it doesn't pollute the public one.
+        __QT_INTERNAL_INSTALL
+    )
+    set(args_single
+        # TODO: Move this into a separate internal function, so it doesn't pollute the public one.
+        __QT_INTERNAL_INSTALL_DIR
+
+        OUTPUT_FILES
+    )
+    set(args_multi
+        MANUAL_MOC_JSON_FILES
+    )
+
     cmake_parse_arguments(arg
-        "__QT_INTERNAL_NO_INSTALL" "INSTALL_DIR" "MANUAL_MOC_JSON_FILES" ${ARGN})
+        "${args_option}"
+        "${args_single}"
+        "${args_multi}" ${ARGN})
 
     get_target_property(target_type ${target} TYPE)
     if (target_type STREQUAL "INTERFACE_LIBRARY")
@@ -1166,33 +1194,40 @@ function(qt6_extract_metatypes target)
     )
     target_sources(${target} INTERFACE ${metatypes_file_genex_build})
 
+    if(arg_OUTPUT_FILES)
+        set(${arg_OUTPUT_FILES} "${metatypes_file}")
+    endif()
+
     # Chech whether the generated json file needs to be installed.
     # Executable metatypes.json files should not be installed. Qt non-prefix builds should also
     # not install the files.
-    set(should_install TRUE)
-    if (target_type STREQUAL "EXECUTABLE" OR arg___QT_INTERNAL_NO_INSTALL)
-        set(should_install "FALSE")
+    set(should_install FALSE)
+
+    if(NOT target_type STREQUAL "EXECUTABLE" AND arg___QT_INTERNAL_INSTALL)
+        set(should_install TRUE)
     endif()
 
     # Automatically fill default install args when not specified.
-    if (NOT arg_INSTALL_DIR)
+    if(NOT arg___QT_INTERNAL_INSTALL_DIR)
         # INSTALL_LIBDIR is not set when QtBuildInternals is not loaded (when not doing a Qt build).
         # Default to a hardcoded location for user projects.
         if(INSTALL_LIBDIR)
-            set(arg_INSTALL_DIR "${INSTALL_LIBDIR}/metatypes")
+            set(install_dir "${INSTALL_LIBDIR}/metatypes")
         else()
-            set(arg_INSTALL_DIR "lib/metatypes")
+            set(install_dir "lib/metatypes")
         endif()
+    else()
+        set(install_dir "${arg___QT_INTERNAL_INSTALL_DIR}")
     endif()
 
     if(should_install)
-        set(metatypes_file_install_path "${arg_INSTALL_DIR}/${metatypes_file_name}")
+        set(metatypes_file_install_path "${install_dir}/${metatypes_file_name}")
         set(metatypes_file_install_path_genex "$<INSTALL_PREFIX>/${metatypes_file_install_path}")
         set(metatypes_file_genex_install
             "$<INSTALL_INTERFACE:$<${consumes_metatypes}:${metatypes_file_install_path_genex}>>"
         )
         target_sources(${target} INTERFACE ${metatypes_file_genex_install})
-        install(FILES "${metatypes_file}" DESTINATION "${arg_INSTALL_DIR}")
+        install(FILES "${metatypes_file}" DESTINATION "${install_dir}")
     endif()
 endfunction()