upgrade to project_options v0.20.0

modernize the cmake build concept too:
 * Import your installed targets with an test to be sure it is usable.
 * Add support for PROJECT_IS_TOP_LEVEL cmake variable
 * Enable conan again as default

CMakeLists.txt

@@ -1,4 +1,4 @@
-cmake_minimum_required(VERSION 3.16)
+cmake_minimum_required(VERSION 3.16...3.23)
 
 # Not ideal to use this global variable, but necessary to make sure
 # that tooling and projects use the same version
@@ -20,11 +20,10 @@ set(ENABLE_DEVELOPER_MODE
 # Change this to false if you want to disable warnings_as_errors in developer mode
 set(OPT_WARNINGS_AS_ERRORS_DEVELOPER_DEFAULT TRUE)
 
-# Add project_options v0.17.0
+# Add project_options v0.20.0
 # https://github.com/cpp-best-practices/project_options
 include(FetchContent)
-FetchContent_Declare(_project_options
-                     URL https://github.com/cpp-best-practices/project_options/archive/refs/tags/v0.17.0.zip)
+FetchContent_Declare(_project_options URL https://github.com/aminya/project_options/archive/refs/tags/v0.20.0.zip)
 FetchContent_MakeAvailable(_project_options)
 include(${_project_options_SOURCE_DIR}/Index.cmake)
 
@@ -40,6 +39,18 @@ project(
   HOMEPAGE_URL "%%myurl%%"
   LANGUAGES CXX C)
 
+# This variable is set by project() in CMake 3.21+
+string(
+  COMPARE EQUAL
+          "${CMAKE_SOURCE_DIR}"
+          "${PROJECT_SOURCE_DIR}"
+          PROJECT_IS_TOP_LEVEL)
+if(PROJECT_IS_TOP_LEVEL)
+  # Consider the CTest module, which creates targets and options!
+  # Only needed if you want to enable submissions to a CDash server.
+  include(CTest)
+endif()
+
 set(GIT_SHA
     "Unknown"
     CACHE STRING "SHA this build was generated from")
@@ -92,6 +103,7 @@ dynamic_project_options(
   PCH_HEADERS
   <vector>
   <string> # This is a list of headers to pre-compile, here are some common ones
+  ENABLE_CONAN
   # CONAN_OPTIONS    # Extra options to pass to conan
   # MSVC_WARNINGS    # Override the defaults for the MSVC warnings
   # CLANG_WARNINGS   # Override the defaults for the CLANG warnings
@@ -100,6 +112,9 @@ dynamic_project_options(
 )
 
 target_compile_features(project_options INTERFACE cxx_std_${CMAKE_CXX_STANDARD})
+# TODO: The INTERFACE library NAMESPACE ALIAS are missing! CK
+add_library(myproject::project_options INTERFACE IMPORTED)
+add_library(myproject::project_warnings INTERFACE IMPORTED)
 
 # configure files based on CMake configuration options
 add_subdirectory(configured_files)
@@ -108,33 +123,42 @@ add_subdirectory(configured_files)
 add_subdirectory(src)
 
 # Adding the tests:
-option(ENABLE_TESTING "Enable the tests" ON)
+option(ENABLE_TESTING "Enable the tests" ${PROJECT_IS_TOP_LEVEL})
 if(ENABLE_TESTING)
   enable_testing()
-  message("Building Tests. Be sure to check out test/constexpr_tests for constexpr
-testing")
+  message(AUTHOR_WARNING "Building Tests. Be sure to check out test/constexpr_tests.cpp for constexpr testing")
   add_subdirectory(test)
 endif()
 
 option(ENABLE_FUZZING "Enable the fuzz tests" OFF)
 if(ENABLE_FUZZING)
-  message("Building Fuzz Tests, using fuzzing sanitizer https://www.llvm.org/docs/LibFuzzer.html")
+  message(AUTHOR_WARNING "Building Fuzz Tests, using fuzzing sanitizer https://www.llvm.org/docs/LibFuzzer.html")
   add_subdirectory(fuzz_test)
 endif()
 
 # If MSVC is being used, and ASAN is enabled, we need to set the debugger environment
 # so that it behaves well with MSVC's debugger, and we can run the target from visual studio
 if(MSVC)
-  get_all_targets(all_targets)
+  get_all_installable_targets(all_targets)
+  message("all_targets=${all_targets}")
   set_target_properties(${all_targets} PROPERTIES VS_DEBUGGER_ENVIRONMENT "PATH=$(VC_ExecutablePath_x64);%PATH%")
 endif()
 
 # set the startup project for the "play" button in MSVC
 set_property(DIRECTORY PROPERTY VS_STARTUP_PROJECT intro)
 
+if(CMAKE_SKIP_INSTALL_RULES)
+  return()
+elseif(NOT PROJECT_IS_TOP_LEVEL)
+  return()
+endif()
+
 # Add other targets that you want installed here, be default we just package the one executable
 # we know we want to ship
-package_project(TARGETS intro)
+package_project(TARGETS intro project_options project_warnings
+  # FIXME: this does not work! CK
+  # PRIVATE_DEPENDENCIES_CONFIGURED project_options project_warnings
+)
 
 # Experience shows that explicit package naming can help make it easier to sort
 # out potential ABI related issues before they start, while helping you

src/CMakeLists.txt

@@ -1,16 +1,12 @@
-find_package(fmt CONFIG)
-find_package(spdlog CONFIG)
-find_package(docopt CONFIG)
+find_package(fmt CONFIG REQUIRED)
+find_package(spdlog CONFIG REQUIRED)
+find_package(docopt CONFIG REQUIRED)
 
 # Generic test that uses conan libs
 add_executable(intro main.cpp)
 target_link_libraries(
   intro
-  PRIVATE project_options
-          project_warnings
-          docopt::docopt
-          fmt::fmt
-          spdlog::spdlog)
+  PUBLIC project_options project_warnings
+  PRIVATE docopt::docopt fmt::fmt spdlog::spdlog)
 
 target_include_directories(intro PRIVATE "${CMAKE_BINARY_DIR}/configured_files/include")
-

src/main.cpp

@@ -27,6 +27,7 @@ static constexpr auto USAGE =
           --drifting    Drifting mine.
 )";
 
+// NOLINTNEXTLINE(bugprone-exception-escape)
 int main(int argc, const char **argv)
 {
   try {
@@ -45,6 +46,6 @@ int main(int argc, const char **argv)
 
     fmt::print("Hello, from {}\n", "{fmt}");
   } catch (const std::exception &e) {
-    fmt::print("Unhandled exception in main: {}", e.what());
+    spdlog::error("Unhandled exception in main: {}", e.what());
   }
 }

test/CMakeLists.txt

@@ -1,25 +1,37 @@
+cmake_minimum_required(VERSION 3.15...3.23)
+
+project(CmakeConfigPackageTests LANGUAGES CXX)
+
+# ---- Test as standalone project the exported config package ----
+
+if(PROJECT_IS_TOP_LEVEL OR TEST_INSTALLED_VERSION)
+  enable_testing()
+
+  find_package(myproject CONFIG REQUIRED) # for intro, project_options, ...
+endif()
+
+# ---- Dependencies ----
+
 find_package(Catch2 REQUIRED)
 
-include(CTest)
 include(Catch)
 
 add_library(catch_main OBJECT catch_main.cpp)
 target_link_libraries(catch_main PUBLIC Catch2::Catch2)
-target_link_libraries(catch_main PRIVATE project_options)
+target_link_libraries(catch_main PRIVATE myproject::project_options)
 
 # Provide a simple smoke test to make sure that the CLI works and can display a --help message
-add_test(NAME cli.has_help COMMAND intro --help)
+add_test(NAME cli.has_help COMMAND myproject::intro --help)
 
 # Provide a test to verify that the version being reported from the application
 # matches the version given to CMake. This will be important once you package
 # your program. Real world shows that this is the kind of simple mistake that is easy
 # to make, but also easy to test for.
-add_test(NAME cli.version_matches COMMAND intro --version)
+add_test(NAME cli.version_matches COMMAND myproject::intro --version)
 set_tests_properties(cli.version_matches PROPERTIES PASS_REGULAR_EXPRESSION "${PROJECT_VERSION}")
 
-
 add_executable(tests tests.cpp)
-target_link_libraries(tests PRIVATE project_warnings project_options catch_main)
+target_link_libraries(tests PRIVATE myproject::project_warnings myproject::project_options catch_main)
 
 # automatically discover tests that are defined in catch based test files you can modify the unittests. Set TEST_PREFIX
 # to whatever you want, or use different for different binaries
@@ -38,7 +50,7 @@ catch_discover_tests(
 
 # Add a file containing a set of constexpr tests
 add_executable(constexpr_tests constexpr_tests.cpp)
-target_link_libraries(constexpr_tests PRIVATE project_options project_warnings catch_main)
+target_link_libraries(constexpr_tests PRIVATE myproject::project_options myproject::project_warnings catch_main)
 
 catch_discover_tests(
   constexpr_tests
@@ -56,7 +68,7 @@ catch_discover_tests(
 # Disable the constexpr portion of the test, and build again this allows us to have an executable that we can debug when
 # things go wrong with the constexpr testing
 add_executable(relaxed_constexpr_tests constexpr_tests.cpp)
-target_link_libraries(relaxed_constexpr_tests PRIVATE project_options project_warnings catch_main)
+target_link_libraries(relaxed_constexpr_tests PRIVATE myproject::project_options myproject::project_warnings catch_main)
 target_compile_definitions(relaxed_constexpr_tests PRIVATE -DCATCH_CONFIG_RUNTIME_STATIC_REQUIRE)
 
 catch_discover_tests(