Introduce QT_SKIP_DEFAULT_TESTCASE_DIRS target property

The property allows skipping to set the QT_TESTCASE_BUILDDIR/SOURCEDIR
definitions. This might be helpful in certain uscases, to optimize the
build by avoiding the need to set the unused compilation flags.

Add the QT_SKIP_DEFAULT_TESTCASE_DIRS variable that is used as the
default value for the QT_SKIP_DEFAULT_TESTCASE_DIRS property.

Task-number: QTBUG-126729
Change-Id: I6fe5bed428175cdd30d21741c20b745d85f3917d
Reviewed-by: Edward Welbourne <edward.welbourne@qt.io>
Reviewed-by: Leena Miettinen <riitta-leena.miettinen@qt.io>
Reviewed-by: Alexandru Croitor <alexandru.croitor@qt.io>

src/testlib/CMakeLists.txt

@@ -7,6 +7,8 @@ include(selfcover.cmake)
 ## Test Module:
 #####################################################################
 
+include("${CMAKE_CURRENT_SOURCE_DIR}/QtTestProperties.cmake")
+
 qt_internal_add_module(Test
     CONFIG_MODULE_NAME testlib
     QMAKE_MODULE_CONFIG console testlib_defines
@@ -80,6 +82,10 @@ qt_internal_add_module(Test
         Qt::CorePrivate
     ATTRIBUTION_FILE_DIR_PATHS
         3rdparty
+    EXTRA_CMAKE_FILES
+        "${CMAKE_CURRENT_SOURCE_DIR}/QtTestProperties.cmake"
+    EXTRA_CMAKE_INCLUDES
+        QtTestProperties.cmake
 )
 
 if(TARGET Gui)
@@ -134,9 +140,15 @@ set(qt_bool_tc_build_dir "$<BOOL:${qt_tc_build_dir}>")
 set(qt_tc_build_dir_def
     "$<IF:${qt_bool_tc_build_dir},${qt_tc_build_dir},$<TARGET_PROPERTY:BINARY_DIR>>"
 )
+
+string(JOIN "" testcase_dirs_genex
+    "$<$<NOT:$<BOOL:$<TARGET_PROPERTY:QT_SKIP_DEFAULT_TESTCASE_DIRS>>>:"
+        "QT_TESTCASE_BUILDDIR=\"${qt_tc_build_dir_def}\"$<SEMICOLON>"
+        "QT_TESTCASE_SOURCEDIR=\"$<TARGET_PROPERTY:SOURCE_DIR>\""
+    ">"
+)
 set_property(TARGET Test APPEND PROPERTY INTERFACE_COMPILE_DEFINITIONS
-    QT_TESTCASE_BUILDDIR="${qt_tc_build_dir_def}"
-    QT_TESTCASE_SOURCEDIR="$<TARGET_PROPERTY:SOURCE_DIR>"
+    ${testcase_dirs_genex}
 )
 
 qt_internal_add_docs(Test

src/testlib/QtTestProperties.cmake

@@ -0,0 +1,27 @@
+# Copyright (C) 2024 The Qt Company Ltd.
+# SPDX-License-Identifier: BSD-3-Clause
+
+# This file contains the property definitions that are known by Qt Test
+
+if(CMAKE_VERSION VERSION_GREATER_EQUAL "3.23")
+    set(qt_skip_default_testcase_dirs_extra_agrs
+        INITIALIZE_FROM_VARIABLE
+        QT_SKIP_DEFAULT_TESTCASE_DIRS
+    )
+elseif(DEFINED QT_SKIP_DEFAULT_TESTCASE_DIRS)
+    message(WARNING "QT_SKIP_DEFAULT_TESTCASE_DIRS is set to ${QT_SKIP_DEFAULT_TESTCASE_DIRS},"
+        " but the variable is not supported by this CMake version. Please set the"
+        " QT_SKIP_DEFAULT_TESTCASE_DIRS target property where is required.")
+endif()
+
+define_property(TARGET
+    PROPERTY
+        QT_SKIP_DEFAULT_TESTCASE_DIRS
+    BRIEF_DOCS
+        "Disables the test case directory definitions for the Qt Test targets."
+    FULL_DOCS
+        "By default the definitions QT_TESTCASE_SOURCEDIR and QT_TESTCASE_BUILDDIR point to the
+        target source and build directories of the target accordingly. If
+        QT_SKIP_DEFAULT_TESTCASE_DIRS is set to TRUE the macros remain empty."
+    ${qt_skip_default_testcase_dirs_extra_agrs}
+)

src/testlib/doc/src/cmake/cmake-properties.qdoc

@@ -0,0 +1,54 @@
+// Copyright (C) 2024 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
+
+/*!
+\group cmake-target-properties-qttest
+\title CMake Target Properties in Qt6 Test
+\brief Lists CMake target properties known to Qt6::Test.
+
+\l{Qt Test} module knows about the following CMake target properties:
+
+\sa{CMake Property Reference}
+*/
+
+/*!
+\page cmake-target-property-qt-skip-default-testcase-dirs.html
+\ingroup cmake-properties-qttest
+\ingroup cmake-target-properties-qttest
+
+\title QT_SKIP_DEFAULT_TESTCASE_DIRS
+\target cmake-target-property-QT_SKIP_DEFAULT_TESTCASE_DIRS
+
+\cmakepropertysince 6.9
+\preliminarycmakeproperty
+
+\brief Disables the test case directory definitions for targets that link
+       to the Test library.
+
+The property disables the following compile-time definitions for the target:
+\list
+\li QT_TESTCASE_SOURCEDIR
+\li QT_TESTCASE_BUILDDIR
+\endlist
+
+By default, these definitions point to the source and build directories
+of the target. Since they are only defined for this target, they preclude
+sharing precompiled headers with the compilation of other targets. If
+\c QT_SKIP_DEFAULT_TESTCASE_DIRS is set to \c TRUE these definitions are
+omitted, avoiding this limitation.
+
+\badcode
+qt_add_executable(mytest main.cpp)
+set_property(TARGET mytest PROPERTY QT_SKIP_DEFAULT_TESTCASE_DIRS TRUE)
+target_link_libraries(mytest PRIVATE Qt6::Test)
+\endcode
+The \c QT_TESTCASE_SOURCEDIR and \c QT_TESTCASE_BUILDDIR macros will remain
+undefined when compiling \c mytest.
+
+The value of the property defaults to the value of the
+\l {cmake-variable-QT_SKIP_DEFAULT_TESTCASE_DIRS}{QT_SKIP_DEFAULT_TESTCASE_DIRS}
+variable.
+
+\sa QFINDTESTDATA,
+    {cmake-variable-QT_SKIP_DEFAULT_TESTCASE_DIRS}{QT_SKIP_DEFAULT_TESTCASE_DIRS}
+*/

src/testlib/doc/src/cmake/cmake-variables.qdoc

@@ -0,0 +1,51 @@
+// Copyright (C) 2024 The Qt Company Ltd.
+// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GFDL-1.3-no-invariants-only
+
+/*!
+\group cmake-variables-qttest
+\title CMake Variables in Qt6 Test
+\brief Lists CMake variables defined in Qt6::Test.
+
+The following CMake variables are defined when Qt6::Test is loaded, for instance
+with
+
+\badcode
+find_package(Qt6 REQUIRED COMPONENTS Test)
+\endcode
+
+\sa{CMake Variable Reference}
+*/
+
+/*!
+\page cmake-variable-qt-skip-default-testcase-dirs.html
+\ingroup cmake-variables-qttest
+
+\title QT_SKIP_DEFAULT_TESTCASE_DIRS
+\target cmake-variable-QT_SKIP_DEFAULT_TESTCASE_DIRS
+
+\cmakevariablesince 6.9
+\preliminarycmakevariable
+
+\summary {Disables the test case directory definitions for the Qt Test targets.}
+
+Controls the default value of the
+\l {cmake-target-property-QT_SKIP_DEFAULT_TESTCASE_DIRS}{QT_SKIP_DEFAULT_TESTCASE_DIRS}
+target property.
+\note Supported by CMake versions >= 3.23.
+
+\badcode
+set(QT_SKIP_DEFAULT_TESTCASE_DIRS TRUE)
+...
+qt_add_executable(mytest1 main1.cpp)
+target_link_libraries(mytest1 PRIVATE Qt6::Test)
+...
+qt_add_executable(mytest2 main2.cpp)
+target_link_libraries(mytest2 PRIVATE Qt6::Test)
+\endcode
+
+The \c QT_TESTCASE_SOURCEDIR and \c QT_TESTCASE_BUILDDIR macros will remain
+undefined when compiling \c mytest1 and \c mytest2.
+
+\sa QFINDTESTDATA,
+    {cmake-target-property-QT_SKIP_DEFAULT_TESTCASE_DIRS}{QT_SKIP_DEFAULT_TESTCASE_DIRS}
+*/