Refactor Metatypes dependency propagation

Every metatypes.json files is now added as an INTERFACE source file to a
target. This enables us later to correctly collect all the
metatypes.json files from dependent targets. This information is also
correctly exported via export()/install().

To avoid the metatypes.json appearing in every target's source list,
the file path is wrapped in a generator expression which will only be
evaluated when the consuming target has the property
QT_CONSUMES_METATYPES set to true. At the moment this is limited to
targets which need to interact with qmltyperegistrar.

Change-Id: I0ffebcd069a923383f7ed11cde2c94ecf2fb13f3
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>

1 files changed, 40 insertions, 116 deletions

diff --git a/src/corelib/Qt6CoreMacros.cmake b/src/corelib/Qt6CoreMacros.cmake
index 1810fdeb65..2bc97c6d12 100644
--- a/src/corelib/Qt6CoreMacros.cmake
+++ b/src/corelib/Qt6CoreMacros.cmake
@@ -595,102 +595,7 @@ if(NOT QT_NO_CREATE_VERSIONLESS_FUNCTIONS)
     endfunction()
 endif()
 
-# Generate metatypes dependency file. This function extracts the list of
-# metatypes files as well as the dependency file from the direct library
-# dependencies of a target via generator expressions.
-# Parameters:
-#   dep_file: Location where to generate the dependency file for build time
-#   dependencies.
-#   dep_file_install: Location where to generate the dependency file which
-#   is expected to be installed.
-function(qt6_generate_meta_types_dep_file target dep_file dep_file_install)
-    # Due to generator expressions it is not possible to recursively evaluate
-    # the LINK_LIBRARIES of target. Therefore we generate a dependency file for
-    # every module with metatypes which can be evaluated at build time.
-    # When generating this file we need to take into account that there are two
-    # levels at which dependencies can be expressed: build and install.
-    # Build dependencies refer to targets which are being built along side the
-    # original target. These targets' install dependencies are not available
-    # at this point in time. We set a special property on these targets that's
-    # only available at build time.
-    # Install dependencies refer to targets which are found via a find_package()
-    # call.
-    # Both install and build targets have the
-    # INTERFACE_QT_META_TYPES_INSTALL_[DEP_FILE|FILE]. When building the target,
-    # INTERFACE_QT_META_TYPES_INSTALL_... refer to the expected install
-    # directory to be appended to CMAKE_INSTALL_PREFIX.
-    # Only build target have the INTERFACE_QT_META_TYPES_[DEP_FILE|FILE] which
-    # point to the files that have been produced during build time.
-    # Finally, to make sure the targets actually have a metatypes files, we
-    # check if they have the INTERFACE_QT_MODULE_HAS_META_TYPES property.
-    #
-    # Note: All properties start with INTERFACE_ since it is the only way to
-    # set properties on interface targets that get generated in the
-    # QtModuleConfig.in
-    #
-    get_target_property(link_dependencies ${target} LINK_LIBRARIES)
-    set(prop_dep "INTERFACE_QT_META_TYPES_BUILD_DEP_FILE")
-    set(prop_file "INTERFACE_QT_META_TYPES_BUILD_FILE")
-    set(prop_file_install "INTERFACE_QT_META_TYPES_INSTALL_FILE")
-    set(prop_dep_install "INTERFACE_QT_META_TYPES_INSTALL_DEP_FILE")
-    set(prop_is_local "INTERFACE_QT_MODULE_META_TYPES_FROM_BUILD")
-    set(prop_has_metatypes "INTERFACE_QT_MODULE_HAS_META_TYPES")
-
-    set(gen_exp "")
-    set(gen_exp_install "")
-    foreach(dep IN LISTS link_dependencies)
-        # Skip over any flags starting with -, like -framework or -lboo.
-        if("${dep}" MATCHES "^-")
-            continue()
-        endif()
-        # replace LINK_ONLY with true, or we will get an error evaluating that
-        # generator expression
-        string(REPLACE "$<LINK_ONLY:" "$<1:" genex_target "$<GENEX_EVAL:${dep}>")
-        string(REPLACE "$<TARGET_OBJECTS:" "$<1:" genex_target "${genex_target}")
-        set(genex_check_is_local
-            "$<TARGET_GENEX_EVAL:${genex_target},$<TARGET_PROPERTY:${genex_target},${prop_is_local}>>"
-        )
-        set(genex_is_target "$<TARGET_EXISTS:$<IF:$<BOOL:${genex_target}>,${genex_target},-NOTFOUND>>")
-        set(genex_has_metatypes
-            "$<TARGET_GENEX_EVAL:${genex_target},$<TARGET_PROPERTY:${genex_target},${prop_has_metatypes}>>"
-        )
-        set(genex_get_metatypes
-            "$<TARGET_GENEX_EVAL:${genex_target},$<TARGET_PROPERTY:${genex_target},${prop_file}>>"
-        )
-        set(genex_get_metatypes_dep
-            "$<TARGET_GENEX_EVAL:${genex_target},$<TARGET_PROPERTY:${genex_target},${prop_dep}>>"
-        )
-        set(genex_get_metatypes_install
-            "$<TARGET_GENEX_EVAL:${genex_target},$<TARGET_PROPERTY:${genex_target},${prop_file_install}>>"
-        )
-        set(genex_get_metatypes_install_dep
-            "$<TARGET_GENEX_EVAL:${genex_target},$<TARGET_PROPERTY:${genex_target},${prop_dep_install}>>"
-        )
-        set(get_local_or_install
-            "$<IF:$<BOOL:${genex_check_is_local}>,${genex_get_metatypes}=${genex_get_metatypes_dep},${genex_get_metatypes_install}=${genex_get_metatypes_install_dep}>"
-        )
-
-        list(APPEND gen_exp
-            "$<$<AND:$<BOOL:${genex_target}>,$<BOOL:${genex_has_metatypes}>>:${get_local_or_install}>"
-        )
-
-        list(APPEND gen_exp_install
-            "$<$<AND:$<BOOL:${genex_target}>,$<BOOL:${genex_get_metatypes_install}>>:${genex_get_metatypes_install}=${genex_get_metatypes_install_dep}>"
-        )
-    endforeach()
-
-    file(GENERATE
-        OUTPUT "${dep_file}"
-        CONTENT "$<JOIN:$<GENEX_EVAL:${gen_exp}>,\n>"
-    )
 
-    file(GENERATE
-        OUTPUT "${dep_file_install}"
-        CONTENT "$<JOIN:$<GENEX_EVAL:${gen_exp_install}>,\n>"
-    )
-endfunction()
-
-#
 # Generate Qt metatypes.json for a target. By default we check whether AUTOMOC
 # has been enabled and we extract the information from that target. Should you
 # not wish to use automoc you need to pass in all the generated json files via the
@@ -808,36 +713,62 @@ function(qt6_generate_meta_types_json_file target)
 
     set(metatypes_file_name "qt6${target_lowercase}_metatypes.json")
     set(metatypes_file "${target_binary_dir}/meta_types/${metatypes_file_name}")
+    set(metatypes_file_gen "${target_binary_dir}/meta_types/${metatypes_file_name}.gen")
 
     set(metatypes_dep_file_name "qt6${target_lowercase}_metatypes_dep.txt")
     set(metatypes_dep_file "${target_binary_dir}/meta_types/${metatypes_dep_file_name}")
 
-    add_custom_command(OUTPUT ${metatypes_file}
+    # Due to generated source file dependency rules being tied to the directory
+    # scope in which they are created it is not possible for other targets which
+    # are defined in a separate scope to see these rules. This leads to failures
+    # in locating the generated source files.
+    # To work around this we write a dummy file to disk to make sure targets
+    # which link against the current target do not produce the error. This dummy
+    # file is then replaced with the contents of the generated file during
+    # build.
+    if (NOT EXISTS ${metatypes_file})
+        file(MAKE_DIRECTORY "${target_binary_dir}/meta_types")
+        file(TOUCH ${metatypes_file})
+    endif()
+    add_custom_command(OUTPUT ${metatypes_file_gen} ${metatypes_file}
         DEPENDS ${QT_CMAKE_EXPORT_NAMESPACE}::moc ${automoc_dependencies} ${manual_dependencies}
         COMMAND ${QT_CMAKE_EXPORT_NAMESPACE}::moc
-            -o ${metatypes_file}
+            -o ${metatypes_file_gen}
             --collect-json ${automoc_args} ${manual_args}
+        COMMAND ${CMAKE_COMMAND} -E copy_if_different
+            ${metatypes_file_gen}
+            ${metatypes_file}
         COMMENT "Runing automoc with --collect-json"
     )
 
-    target_sources(${target} PRIVATE ${metatypes_file})
+    # We still need to add this file as a source of Core, otherwise the file
+    # rule above is not triggered. INTERFACE_SOURCES do not properly register
+    # as dependencies to build the current target.
+    target_sources(${target} PRIVATE ${metatypes_file_gen})
+    set(metatypes_file_genex_build)
+    set(metatypes_file_genex_install)
+    if (arg_COPY_OVER_INSTALL)
+        set(metatypes_file_genex_build
+            "$<BUILD_INTERFACE:$<$<BOOL:$<TARGET_PROPERTY:QT_CONSUMES_METATYPES>>:${arg_INSTALL_DIR}/${metatypes_file_name}>>"
+        )
+    else()
+        set(metatypes_file_genex_build
+            "$<BUILD_INTERFACE:$<$<BOOL:$<TARGET_PROPERTY:QT_CONSUMES_METATYPES>>:${metatypes_file}>>"
+        )
+        set(metatypes_file_genex_install
+            "$<INSTALL_INTERFACE:$<$<BOOL:$<TARGET_PROPERTY:QT_CONSUMES_METATYPES>>:$<INSTALL_PREFIX>/${arg_INSTALL_DIR}/${metatypes_file_name}>>"
+        )
+    endif()
     set_source_files_properties(${metatypes_file} PROPERTIES HEADER_FILE_ONLY TRUE)
 
-    # Set the required properties. See documentation of
-    # qt6_generate_meta_types_dep_file()
     set_target_properties(${target} PROPERTIES
         INTERFACE_QT_MODULE_HAS_META_TYPES YES
         INTERFACE_QT_MODULE_META_TYPES_FROM_BUILD YES
         INTERFACE_QT_META_TYPES_BUILD_FILE ${metatypes_file}
-        INTERFACE_QT_META_TYPES_BUILD_DEP_FILE ${metatypes_dep_file}
-        INTERFACE_QT_META_TYPES_INSTALL_FILE "${arg_INSTALL_DIR}/${metatypes_file_name}"
-        INTERFACE_QT_META_TYPES_INSTALL_DEP_FILE "${arg_INSTALL_DIR}/${metatypes_dep_file_name}"
+        QT_MODULE_META_TYPES_FILE_GENEX_BUILD "${metatypes_file_genex_build}"
+        QT_MODULE_META_TYPES_FILE_GENEX_INSTALL "${metatypes_file_genex_install}"
     )
-
-    qt6_generate_meta_types_dep_file(${target}
-        "${metatypes_dep_file}"
-        "${metatypes_dep_file}.install"
-   )
+    target_sources(${target} INTERFACE ${metatypes_file_genex_build} ${metatypes_file_genex_install})
 
     if (arg_COPY_OVER_INSTALL)
         get_target_property(target_type ${target} TYPE)
@@ -845,13 +776,10 @@ function(qt6_generate_meta_types_json_file target)
             COMMAND ${CMAKE_COMMAND} -E copy_if_different
                 "${metatypes_file}"
                 "${arg_INSTALL_DIR}/${metatypes_file_name}"
-            COMMAND ${CMAKE_COMMAND} -E copy_if_different
-                "${metatypes_dep_file}.install"
-                "${arg_INSTALL_DIR}/${metatypes_dep_file_name}"
         )
         if (target_type STREQUAL "OBJECT_LIBRARY")
             add_custom_target(${target}_metatypes_copy
-                DEPENDS "${metatypes_file}" "${metatypes_dep_file}"
+                DEPENDS "${metatypes_file}"
                 ${command_args}
             )
             add_dependencies(${target} ${target}_metatypes_copy)
@@ -864,10 +792,6 @@ function(qt6_generate_meta_types_json_file target)
         install(FILES "${metatypes_file}"
             DESTINATION "${arg_INSTALL_DIR}"
         )
-        install(FILES "${metatypes_dep_file}.install"
-            DESTINATION "${arg_INSTALL_DIR}"
-            RENAME "${metatypes_dep_file_name}"
-        )
     endif()
 endfunction()