Automatically download GTest on Windows

CMakeLists.txt

@@ -66,6 +66,7 @@ endif()
 
 option(CLIENT "Compile client" ON)
 option(DOWNLOAD_DEPENDENCIES "Download dependencies (only available on Windows)" ${AUTO_DEPENDENCIES_DEFAULT})
+option(DOWNLOAD_GTEST "Download and compile GTest if not found" ${AUTO_DEPENDENCIES_DEFAULT})
 option(PREFER_BUNDLED_LIBS "Prefer bundled libraries over system libraries" ${AUTO_DEPENDENCIES_DEFAULT})
 option(DEV "Don't generate stuff necessary for packaging" OFF)
 
@@ -348,7 +349,16 @@ if(CLIENT AND NOT(SDL2_FOUND))
   message(SEND_ERROR "You must install SDL2 to compile the Teeworlds client")
 endif()
 if(NOT(GTEST_FOUND))
-  message(STATUS "To run the tests, you have to install GTest")
+  if(DOWNLOAD_GTEST)
+    if(GIT_FOUND)
+      message(STATUS "Automatically downloading GTest to be able to run tests")
+    else()
+      set(DOWNLOAD_GTEST OFF)
+      message(WARNING "To automatically download GTest, you have to install Git")
+    endif()
+  else()
+    message(STATUS "To run the tests, you have to install GTest")
+  endif()
 endif()
 
 if(TARGET_OS STREQUAL "windows")
@@ -375,6 +385,57 @@ else()
   endif()
 endif()
 
+########################################################################
+# DOWNLOAD GTEST
+########################################################################
+
+if(NOT(GTEST_FOUND) AND DOWNLOAD_GTEST)
+  set(TEEWORLDS_GTEST_VERSION release-1.8.1)
+  configure_file(cmake/Download_GTest_CMakeLists.txt.in googletest-download/CMakeLists.txt)
+  execute_process(COMMAND ${CMAKE_COMMAND} -G "${CMAKE_GENERATOR}" .
+    RESULT_VARIABLE result
+    WORKING_DIRECTORY ${PROJECT_BINARY_DIR}/googletest-download
+  )
+  if(result)
+    message(WARNING "CMake step for googletest failed: ${result}")
+    set(DOWNLOAD_GTEST OFF)
+  else()
+    execute_process(COMMAND ${CMAKE_COMMAND} --build .
+      RESULT_VARIABLE result
+      WORKING_DIRECTORY ${PROJECT_BINARY_DIR}/googletest-download
+    )
+    if(result)
+      message(WARNING "Build step for googletest failed: ${result}")
+      set(DOWNLOAD_GTEST OFF)
+    else()
+      # Prevent overriding the parent project's compiler/linker settings on Windows
+      set(gtest_force_shared_crt ON CACHE BOOL "" FORCE)
+
+      # Add googletest directly to our build. This defines the gtest target.
+      add_subdirectory(
+        ${PROJECT_BINARY_DIR}/googletest-src
+        ${PROJECT_BINARY_DIR}/googletest-build
+        EXCLUDE_FROM_ALL
+      )
+
+      if(MSVC)
+        foreach(target gtest)
+          # `/w` disables all warnings. This is needed because `gtest` enables
+          # `/WX` (equivalent of `-Werror`) for some reason, breaking builds
+          # when MSVS adds new warnings.
+          target_compile_options(${target} PRIVATE $<$<NOT:${DBG}>:/MT> $<${DBG}:/MTd> /w)
+        endforeach()
+      endif()
+
+      set(GTEST_LIBRARIES gtest)
+      set(GTEST_INCLUDE_DIRS)
+      if(CMAKE_VERSION VERSION_LESS 2.8.11)
+        set(GTEST_INCLUDE_DIRS "${gtest_SOURCE_DIR}/include")
+      endif()
+    endif()
+  endif()
+endif()
+
 ########################################################################
 # DEPENDENCY COMPILATION
 ########################################################################
@@ -1486,7 +1547,7 @@ add_custom_target(everything DEPENDS ${TARGETS_OWN})
 # TESTS
 ########################################################################
 
-if(GTEST_FOUND)
+if(GTEST_FOUND OR DOWNLOAD_GTEST)
   set_src(TESTS GLOB src/test
     fs.cpp
     git_revision.cpp

cmake/Download_GTest_CMakeLists.txt.in

@@ -0,0 +1,16 @@
+cmake_minimum_required(VERSION 2.8)
+
+project(googletest-download NONE)
+
+include(ExternalProject)
+ExternalProject_Add(googletest
+  GIT_REPOSITORY    https://github.com/google/googletest.git
+  GIT_TAG           "${TEEWORLDS_GTEST_VERSION}"
+  SOURCE_DIR        "${CMAKE_BINARY_DIR}/googletest-src"
+  BINARY_DIR        "${CMAKE_BINARY_DIR}/googletest-build"
+  CONFIGURE_COMMAND ""
+  BUILD_COMMAND     ""
+  INSTALL_COMMAND   ""
+  TEST_COMMAND      ""
+  TLS_VERIFY        ON
+)