vcpkg/scripts/cmake/vcpkg_test_cmake.cmake

## # vcpkg_test_cmake
##
## Tests a built package for CMake `find_package()` integration.
##
## ## Usage:
## ```cmake
## vcpkg_test_cmake(PACKAGE_NAME <name> [MODULE])
## ```
##
## ## Parameters:
##
## ### PACKAGE_NAME
## The expected name to find with `find_package()`.
##
## ### MODULE
## Indicates that the library expects to be found via built-in CMake targets.
##
function(vcpkg_test_cmake)
  # The following issues need to be addressed before re-enabling this function.
  #   1. Use the actual vcpkg toolchain file.
  #   2. Select a generator in the same method as vcpkg_configure_cmake() as though the PREFER_NINJA flag was always passed.
  #   3. Fully emulate the toolchain file for the just-built package (just adding it to CMAKE_PREFIX_PATH is not enough).
  return()

  cmake_parse_arguments(_tc "MODULE" "PACKAGE_NAME" "" ${ARGN})

  if(NOT DEFINED _tc_PACKAGE_NAME)
    message(FATAL_ERROR "PACKAGE_NAME must be specified")
  endif()
  if(_tc_MODULE)
    set(PACKAGE_TYPE MODULE)
  else()
    set(PACKAGE_TYPE CONFIG)
  endif()

  if(VCPKG_PLATFORM_TOOLSET STREQUAL "v142")
    message(STATUS "Skipping CMake integration test due to v142 / CMake interaction issues")
    return()
  endif()

  message(STATUS "Performing CMake integration test")
  file(REMOVE_RECURSE ${CURRENT_BUILDTREES_DIR}/${TARGET_TRIPLET}-test)
  file(MAKE_DIRECTORY ${CURRENT_BUILDTREES_DIR}/${TARGET_TRIPLET}-test)

  #Generate Dummy source
#    set(VCPKG_TEST_SOURCE ${CURRENT_BUILDTREES_DIR}/${TARGET_TRIPLET}-test/CMakeIntegration.cpp)
#    file(WRITE  ${VCPKG_TEST_SOURCE} "int main() \{\n")
#    file(APPEND ${VCPKG_TEST_SOURCE} "return 0;}")
  # Generate test source CMakeLists.txt
  set(VCPKG_TEST_CMAKELIST ${CURRENT_BUILDTREES_DIR}/${TARGET_TRIPLET}-test/CMakeLists.txt)
  file(WRITE  ${VCPKG_TEST_CMAKELIST} "cmake_minimum_required(VERSION 3.10)\n")
  file(APPEND ${VCPKG_TEST_CMAKELIST} "set(CMAKE_PREFIX_PATH \"${CURRENT_PACKAGES_DIR};${CURRENT_INSTALLED_DIR}\")\n")
  file(APPEND ${VCPKG_TEST_CMAKELIST} "\n")
  file(APPEND ${VCPKG_TEST_CMAKELIST} "find_package(${_tc_PACKAGE_NAME} ${PACKAGE_TYPE} REQUIRED)\n")
  #To properly test if the package is actually working haveway correctly we have to link all targets of a package to 
  #a test executable and than actually build it. This will not discover if every symbol exported by the library is available/linked
  #but it will doscover if all files which are linked by a target actual exist. Problem is: How to discover all targets?
#    file(APPEND ${VCPKG_TEST_CMAKELIST} "add_executable(${_tc_PACKAGE_NAME}_exe ${VCPKG_TEST_SOURCE})\n")
#    file(APPEND ${VCPKG_TEST_CMAKELIST} "target_link_libraries(${_tc_PACKAGE_NAME}_exe PRIVATE ${_tc_PACKAGE_NAME})\n")

  if(DEFINED _VCPKG_CMAKE_GENERATOR)
      set(VCPKG_CMAKE_TEST_GENERATOR "${_VCPKG_CMAKE_GENERATOR}")
  else()
      set(VCPKG_CMAKE_TEST_GENERATOR Ninja)
  endif()

  # Run cmake config with a generated CMakeLists.txt
  set(LOGPREFIX "${CURRENT_BUILDTREES_DIR}/test-cmake-${TARGET_TRIPLET}")
  execute_process(
    COMMAND ${CMAKE_COMMAND} -G ${VCPKG_CMAKE_TEST_GENERATOR} .
    OUTPUT_FILE "${LOGPREFIX}-out.log"
    ERROR_FILE "${LOGPREFIX}-err.log"
    RESULT_VARIABLE error_code
    WORKING_DIRECTORY ${CURRENT_BUILDTREES_DIR}/${TARGET_TRIPLET}-test
  )
  if(error_code)
    message(FATAL_ERROR "CMake integration test failed; unable to find_package(${_tc_PACKAGE_NAME} ${PACKAGE_TYPE} REQUIRED)")
  endif()
endfunction()