Add support for building and installing repo target sets

Introduce the concept of repository target sets, which is a named set of
targets within a Qt module repository.

In a Qt repository, a repo target set 'qtfoo' can be defined in the
top-level project file with
    qt_internal_define_repo_target_set(qtfoo DEPENDS Bar Baz)

The DEPENDS argument specifies Qt components that need to be
find_package'd when building the targets that belong to qtfoo.

In subdirectory project files, use
qt_internal_include_in_repo_target_set(qtfoo) to mark the file as
belonging to the repo target set.

To build and install a single repo target set, specify
QT_BUILD_SINGLE_REPO_TARGET_SET=qtfoo when configuring the Qt
repository.

Change-Id: Ic9e6213e3225988fd561f315bc857ee44ff17420
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>

4 files changed, 57 insertions, 0 deletions

diff --git a/cmake/QtBaseGlobalTargets.cmake b/cmake/QtBaseGlobalTargets.cmake
index 54891f9206..09f1a4de6b 100644
--- a/cmake/QtBaseGlobalTargets.cmake
+++ b/cmake/QtBaseGlobalTargets.cmake
@@ -225,6 +225,7 @@ qt_copy_or_install(FILES
                    cmake/QtSeparateDebugInfo.cmake
                    cmake/QtSetup.cmake
                    cmake/QtSimdHelpers.cmake
+                   cmake/QtSingleRepoTargetSetBuildHelpers.cmake
                    cmake/QtStandaloneTestsConfig.cmake.in
                    cmake/QtSyncQtHelpers.cmake
                    cmake/QtTargetHelpers.cmake
diff --git a/cmake/QtBuild.cmake b/cmake/QtBuild.cmake
index d246685952..49c874575c 100644
--- a/cmake/QtBuild.cmake
+++ b/cmake/QtBuild.cmake
@@ -534,6 +534,7 @@ include(QtRpathHelpers)
 include(QtSanitizerHelpers)
 include(QtScopeFinalizerHelpers)
 include(QtSimdHelpers)
+include(QtSingleRepoTargetSetBuildHelpers)
 include(QtSyncQtHelpers)
 include(QtTargetHelpers)
 include(QtTestHelpers)
diff --git a/cmake/QtBuildInternals/QtBuildInternalsConfig.cmake b/cmake/QtBuildInternals/QtBuildInternalsConfig.cmake
index 4928573349..a173c0bcbc 100644
--- a/cmake/QtBuildInternals/QtBuildInternalsConfig.cmake
+++ b/cmake/QtBuildInternals/QtBuildInternalsConfig.cmake
@@ -324,6 +324,50 @@ macro(qt_prepare_standalone_project)
     qt_enable_cmake_languages()
 endmacro()
 
+# Define a repo target set, and store accompanying information.
+#
+# A repo target set is a subset of targets in a Qt module repository. To build a repo target set,
+# set QT_BUILD_SINGLE_REPO_TARGET_SET to the name of the repo target set.
+#
+# This function is to be called in the top-level project file of a repository,
+# before qt_internal_prepare_single_repo_target_set_build()
+#
+# This function stores information in variables of the parent scope.
+#
+# Positional Arguments:
+#   name - The name of this repo target set.
+#
+# Named Arguments:
+#   DEPENDS - List of Qt6 COMPONENTS that are build dependencies of this repo target set.
+function(qt_internal_define_repo_target_set name)
+    set(oneValueArgs DEPENDS)
+    set(prefix QT_REPO_TARGET_SET_)
+    cmake_parse_arguments(${prefix}${name} "" ${oneValueArgs} "" ${ARGN})
+    foreach(arg IN LISTS oneValueArgs)
+        set(${prefix}${name}_${arg} ${${prefix}${name}_${arg}} PARENT_SCOPE)
+    endforeach()
+    set(QT_REPO_KNOWN_TARGET_SETS "${QT_REPO_KNOWN_TARGET_SETS};${name}" PARENT_SCOPE)
+endfunction()
+
+# Setup a single repo target set build if QT_BUILD_SINGLE_REPO_TARGET_SET is defined.
+#
+# This macro must be called in the top-level project file of the repository after all repo target
+# sets have been defined.
+macro(qt_internal_prepare_single_repo_target_set_build)
+    if(DEFINED QT_BUILD_SINGLE_REPO_TARGET_SET)
+        if(NOT QT_BUILD_SINGLE_REPO_TARGET_SET IN_LIST QT_REPO_KNOWN_TARGET_SETS)
+            message(FATAL_ERROR
+                "Repo target set '${QT_BUILD_SINGLE_REPO_TARGET_SET}' is undefined.")
+        endif()
+        message(STATUS
+            "Preparing single repo target set build of ${QT_BUILD_SINGLE_REPO_TARGET_SET}")
+        if (NOT "${QT_REPO_TARGET_SET_${QT_BUILD_SINGLE_REPO_TARGET_SET}_DEPENDS}" STREQUAL "")
+            find_package(${INSTALL_CMAKE_NAMESPACE} ${PROJECT_VERSION} CONFIG REQUIRED
+                COMPONENTS ${QT_REPO_TARGET_SET_${QT_BUILD_SINGLE_REPO_TARGET_SET}_DEPENDS})
+        endif()
+    endif()
+endmacro()
+
 macro(qt_build_repo_begin)
     qt_build_internals_set_up_private_api()
     qt_enable_cmake_languages()
diff --git a/cmake/QtSingleRepoTargetSetBuildHelpers.cmake b/cmake/QtSingleRepoTargetSetBuildHelpers.cmake
new file mode 100644
index 0000000000..789b23b6e6
--- /dev/null
+++ b/cmake/QtSingleRepoTargetSetBuildHelpers.cmake
@@ -0,0 +1,11 @@
+# Macro that checks for a single repo target set build, and returns from the current file, directory
+# or function. Use this at the top of project files to whitelist the file for the given package.
+macro(qt_internal_include_in_repo_target_set _repo_target_set_name)
+    if(DEFINED QT_BUILD_SINGLE_REPO_TARGET_SET)
+        if(NOT "${_repo_target_set_name}" STREQUAL QT_BUILD_SINGLE_REPO_TARGET_SET)
+            message(STATUS "Not part of repo target set ${QT_BUILD_SINGLE_REPO_TARGET_SET}: "
+                "${CMAKE_CURRENT_LIST_DIR}")
+            return()
+        endif()
+    endif()
+endmacro()