From dc467ebdfa24ebbd1db62e07a3961ebb4a90fb74 Mon Sep 17 00:00:00 2001
From: James Turner <james@flightgear.org>
Date: Sun, 8 Jan 2023 19:35:29 +0000
Subject: [PATCH] Cmake Improve Finder for CppUnit

Define an imported target for the system CppUnit, so we can
correctly pass includes locations to FgfsTestSuite
---
 CMakeLists.txt                 |  3 ++-
 CMakeModules/FindCppUnit.cmake | 10 ++++++++++
 test_suite/CMakeLists.txt      |  6 +++---
 3 files changed, 15 insertions(+), 4 deletions(-)

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 1500a1d41..889ecb9ec 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -183,7 +183,7 @@ option(SYSTEM_SPEEX      "Set to ON to build IAXClient with the system's speex a
 option(SYSTEM_GSM        "Set to ON to build IAXClient with the system's GSM library" ${SYSTEM_GSM_DEFAULT})
 option(SYSTEM_FLITE      "Set to ON to build Flightgear with the system's Flite library" ${SYSTEM_FLITE_DEFAULT})
 option(SYSTEM_HTS_ENGINE "Set to ON to build Flightgear with the system's HTS Engine library" ${SYSTEM_HTS_ENGINE_DEFAULT})
-option(SYSTEM_CPPUNIT    "Set to ON to build Flightgear with the system's CppUnit library")
+option(SYSTEM_CPPUNIT    "Set to ON to build Flightgear with the system's CppUnit library" OFF)
 
 # additional utilities
 option(ENABLE_FGELEV     "Set to ON to build the fgelev application (default)" ON)
@@ -266,6 +266,7 @@ endif(EVENT_INPUT)
 include(SetupSwiftLibraries)
 
 if (SYSTEM_CPPUNIT)
+    message(STATUS "Looking for system CppUnit")
     find_package(CppUnit REQUIRED)
 endif()
 
diff --git a/CMakeModules/FindCppUnit.cmake b/CMakeModules/FindCppUnit.cmake
index 3b9b638d3..7b5593868 100644
--- a/CMakeModules/FindCppUnit.cmake
+++ b/CMakeModules/FindCppUnit.cmake
@@ -4,6 +4,8 @@
 # CPPUNIT_FOUND
 # CPPUNIT_LIBRARIES
 # CPPUNIT_INCLUDE_DIR
+#
+# And defines the imported target CppUnitLib
 
 # Find CppUnit.
 if (NOT CPPUNIT_LIBRARIES AND NOT CPPUNIT_INCLUDE_DIR)
@@ -39,4 +41,12 @@ if (CPPUNIT_LIBRARIES AND CPPUNIT_INCLUDE_DIR)
     set(CPPUNIT_FOUND TRUE)
     message(STATUS "CppUnit library found: ${CPPUNIT_LIBRARIES}")
     message(STATUS "CppUnit include directory found: ${CPPUNIT_INCLUDE_DIR}")
+
+    if(NOT TARGET CppUnitLib)
+        add_library(CppUnitLib UNKNOWN IMPORTED)
+        set_target_properties(CppUnitLib PROPERTIES
+            INTERFACE_INCLUDE_DIRECTORIES "${CPPUNIT_INCLUDE_DIR}"
+            IMPORTED_LOCATION "${CPPUNIT_LIBRARIES}")
+    endif()
 endif ()
+
diff --git a/test_suite/CMakeLists.txt b/test_suite/CMakeLists.txt
index 15f8153e5..188b35cc0 100644
--- a/test_suite/CMakeLists.txt
+++ b/test_suite/CMakeLists.txt
@@ -54,8 +54,8 @@ if (NOT SYSTEM_CPPUNIT)
     add_library(CppUnitLib STATIC ${CPPUNIT_SOURCES} ${CPPUNIT_HEADERS})
 
     target_include_directories(CppUnitLib PUBLIC "${PROJECT_SOURCE_DIR}/3rdparty/cppunit/include")
-
-    set(CPPUNIT_LIBRARIES CppUnitLib)
+elseif(NOT TARGET CppUnitLib)
+    message(FATAL_ERROR "CppUnit: system CppUnit library not found correctly")
 else()
     message(STATUS "CppUnit: Linking to the system supplied CppUnit library")
 endif()
@@ -151,7 +151,7 @@ target_include_directories(fgfs_test_suite PUBLIC ${PROJECT_SOURCE_DIR})
 target_compile_definitions(fgfs_test_suite PUBLIC BUILDING_TESTSUITE)
 
 # Additional libraries just for the test suite.
-target_link_libraries(fgfs_test_suite ${CPPUNIT_LIBRARIES})
+target_link_libraries(fgfs_test_suite CppUnitLib)
 
 # target to run the tests
 if (MSVC)