CMake build: generate pkgconfig for public modules

After the update to the CMake based build system the ability to
generate pkgconfig files, like it was with QMake, was lost.

This patch adds pkgconfig generation again via a new internal command
named qt_internal_export_pkg_config_file.

The functionality of this command consists in checking if the target
is internal. Then gets the compile definitions. It performs a search
for dependencies that is somewhat similar to
qt_get_direct_module_dependencies, although it won't recurse down for
more deps. Each dependency is then again, checked if it's internal or
has a public interface. Later these deps get deduplicated and lastly
a pkgconfig file is filled.

The resulting pkgconfig files of many of the Qt6 packages were
validated via invocations of `pkg-config --validate` and
`pkg-config --simulate` commands and later used to build local
projects plus tests that use the pkg-config provided details at
compilation time.

Although it has some limitations, with qt_internal_add_qml_module if
it specifies non-public deps these won't be listed and with non-Qt
requirements, notably in static builds, not being appended to the
PkgConfig file.

Task-number: QTBUG-86080
Change-Id: I0690bb3ca729eec328500f227261db9b7e7628f6
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>

1 files changed, 32 insertions, 18 deletions

diff --git a/cmake/QtPublicWalkLibsHelpers.cmake b/cmake/QtPublicWalkLibsHelpers.cmake
index 7267bc9677..85f09b7679 100644
--- a/cmake/QtPublicWalkLibsHelpers.cmake
+++ b/cmake/QtPublicWalkLibsHelpers.cmake
@@ -73,6 +73,8 @@ endfunction()
 #                           Used for prl file generation.
 #            'promote_global' promotes walked imported targets to global scope.
 #            'collect_targets' collects all target names (discards framework or link flags)
+#            'direct_targets' collects only the direct target names (discards framework or link
+#                             flags)
 #
 #
 function(__qt_internal_walk_libs
@@ -83,6 +85,12 @@ function(__qt_internal_walk_libs
     endif()
     list(APPEND collected ${target})
 
+    if(operation MATCHES "^direct")
+        set(direct TRUE)
+    else()
+        set(direct FALSE)
+    endif()
+
     if(target STREQUAL "${QT_CMAKE_EXPORT_NAMESPACE}::EntryPointPrivate")
         # We can't (and don't need to) process EntryPointPrivate because it brings in
         # $<TARGET_PROPERTY:prop> genexes which get replaced with
@@ -184,21 +192,25 @@ function(__qt_internal_walk_libs
                 endif()
                 get_target_property(lib_target_type ${lib_target} TYPE)
                 if(lib_target_type STREQUAL "INTERFACE_LIBRARY")
-                    __qt_internal_walk_libs(
-                        ${lib_target}
-                        lib_libs_${target}
-                        lib_rcc_objects_${target}
-                        "${dict_name}" "${operation}" ${collected})
-                    if(lib_libs_${target})
-                        __qt_internal_merge_libs(libs ${lib_libs_${target}})
-                        set(is_module 0)
-                    endif()
-                    if(lib_rcc_objects_${target})
-                        __qt_internal_merge_libs(rcc_objects ${lib_rcc_objects_${target}})
+                    if(NOT ${direct})
+                        __qt_internal_walk_libs(
+                            ${lib_target}
+                            lib_libs_${target}
+                            lib_rcc_objects_${target}
+                            "${dict_name}" "${operation}" ${collected})
+                        if(lib_libs_${target})
+                            __qt_internal_merge_libs(libs ${lib_libs_${target}})
+                            set(is_module 0)
+                        endif()
+                        if(lib_rcc_objects_${target})
+                            __qt_internal_merge_libs(rcc_objects ${lib_rcc_objects_${target}})
+                        endif()
+                    else()
+                        __qt_internal_merge_libs(libs ${lib})
                     endif()
                 elseif(NOT lib_target_type STREQUAL "OBJECT_LIBRARY")
 
-                    if(operation STREQUAL "collect_targets")
+                    if(operation MATCHES "^(collect|direct)_targets$")
                         __qt_internal_merge_libs(libs ${lib_target})
                     else()
                         __qt_internal_merge_libs(libs "$<TARGET_LINKER_FILE:${lib_target}>")
@@ -209,11 +221,13 @@ function(__qt_internal_walk_libs
                         __qt_internal_merge_libs(rcc_objects ${target_rcc_objects})
                     endif()
 
-                    __qt_internal_walk_libs(
-                        ${lib_target}
-                        lib_libs_${target}
-                        lib_rcc_objects_${target}
-                        "${dict_name}" "${operation}" ${collected})
+                    if(NOT ${direct})
+                        __qt_internal_walk_libs(
+                            ${lib_target}
+                            lib_libs_${target}
+                            lib_rcc_objects_${target}
+                            "${dict_name}" "${operation}" ${collected})
+                    endif()
                     if(lib_libs_${target})
                         __qt_internal_merge_libs(libs ${lib_libs_${target}})
                     endif()
@@ -242,7 +256,7 @@ function(__qt_internal_walk_libs
                 message(FATAL_ERROR "The ${CMAKE_MATCH_1} target is mentioned as a dependency for \
 ${target}, but not declared.")
             else()
-                if(NOT operation STREQUAL "collect_targets")
+                if(NOT operation MATCHES "^(collect|direct)_targets$")
                     set(final_lib_name_to_merge "${lib_target}")
                     if(lib_target MATCHES "/([^/]+).framework$")
                         set(final_lib_name_to_merge "-framework ${CMAKE_MATCH_1}")