ExternalProject: Use CMP0114 NEW behavior with Xcode "new build system"

The ExternalProject module cannot be implemented in the Xcode "new build
system" without using CMP0114's NEW behavior.  When configuring for that
build system, warn if the policy is not set to NEW and use NEW behavior
anyway.

Modules/ExternalProject.cmake

@@ -3342,6 +3342,18 @@ function(ExternalProject_Add name)
   cmake_policy(GET CMP0114 cmp0114
     PARENT_SCOPE # undocumented, do not use outside of CMake
     )
+  if(CMAKE_XCODE_BUILD_SYSTEM VERSION_GREATER_EQUAL 12 AND NOT cmp0114 STREQUAL "NEW")
+    message(AUTHOR_WARNING
+      "Policy CMP0114 is not set to NEW.  "
+      "In order to support the Xcode \"new build system\", "
+      "this project must be updated to set policy CMP0114 to NEW."
+      "\n"
+      "Since CMake is generating for the Xcode \"new build system\", "
+      "ExternalProject_Add will use policy CMP0114's NEW behavior anyway, "
+      "but the generated build system may not match what the project intends."
+      )
+    set(cmp0114 "NEW")
+  endif()
 
   _ep_get_configuration_subdir_suffix(cfgdir)
 

Modules/FetchContent/CMakeLists.cmake.in

@@ -2,6 +2,7 @@
 # file Copyright.txt or https://cmake.org/licensing for details.
 
 cmake_minimum_required(VERSION ${CMAKE_VERSION})
+cmake_policy(SET CMP0114 NEW)
 
 # We name the project and the target for the ExternalProject_Add() call
 # to something that will highlight to the user what we are working on if

Tests/ExternalProject/CMakeLists.txt

@@ -1,5 +1,8 @@
 cmake_minimum_required(VERSION 2.8)
 project(ExternalProjectTest NONE)
+if(CMAKE_XCODE_BUILD_SYSTEM VERSION_GREATER_EQUAL 12)
+  cmake_policy(SET CMP0114 NEW)
+endif()
 
 include(ExternalProject)
 

Tests/ExternalProjectLocal/CMakeLists.txt

@@ -1,5 +1,8 @@
 cmake_minimum_required(VERSION 2.8)
 project(ExternalProjectLocalTest NONE)
+if(CMAKE_XCODE_BUILD_SYSTEM VERSION_GREATER_EQUAL 12)
+  cmake_policy(SET CMP0114 NEW)
+endif()
 
 include(ExternalProject)
 

Tests/ExternalProjectUpdate/CMakeLists.txt

@@ -1,5 +1,9 @@
 cmake_minimum_required(VERSION 2.8)
 project(ExternalProjectUpdateTest NONE)
+if(CMAKE_XCODE_BUILD_SYSTEM VERSION_GREATER_EQUAL 12)
+  cmake_policy(SET CMP0114 NEW)
+endif()
+cmake_policy(GET CMP0114 cmp0114)
 
 include(ExternalProject)
 
@@ -18,8 +22,16 @@ set_property(GLOBAL PROPERTY PREDEFINED_TARGETS_FOLDER
 set(base "${CMAKE_BINARY_DIR}/CMakeExternals")
 set(binary_base "${base}/Build")
 set_property(DIRECTORY PROPERTY EP_BASE ${base})
-set_property(DIRECTORY PROPERTY EP_STEP_TARGETS configure build test)
-set_property(DIRECTORY PROPERTY EP_INDEPENDENT_STEP_TARGETS update)
+if(cmp0114 STREQUAL "NEW")
+  set_property(DIRECTORY PROPERTY EP_STEP_TARGETS configure build test update)
+  set(TestUpdateCommand_STEP_TARGETS STEP_TARGETS update)
+  set(TestUpdateCommand_INDEPENDENT_STEP_TARGETS)
+else()
+  set_property(DIRECTORY PROPERTY EP_STEP_TARGETS configure build test)
+  set_property(DIRECTORY PROPERTY EP_INDEPENDENT_STEP_TARGETS update)
+  set(TestUpdateCommand_STEP_TARGETS)
+  set(TestUpdateCommand_INDEPENDENT_STEP_TARGETS INDEPENDENT_STEP_TARGETS update)
+endif()
 
 ExternalProject_Add(TestUpdateCommand
   SOURCE_DIR ${CMAKE_CURRENT_SOURCE_DIR}
@@ -28,7 +40,8 @@ ExternalProject_Add(TestUpdateCommand
   CONFIGURE_COMMAND ""
   BUILD_COMMAND ""
   INSTALL_COMMAND ""
-  INDEPENDENT_STEP_TARGETS update
+  ${TestUpdateCommand_STEP_TARGETS}
+  ${TestUpdateCommand_INDEPENDENT_STEP_TARGETS}
   )
 add_custom_target(TestUpdateCommandDriver ALL)
 add_dependencies(TestUpdateCommandDriver TestUpdateCommand-update)

Tests/RunCMake/CMakeLists.txt

@@ -569,6 +569,9 @@ add_RunCMake_test(file-GET_RUNTIME_DEPENDENCIES
 add_RunCMake_test(CPackCommandLine)
 add_RunCMake_test(CPackConfig)
 add_RunCMake_test(CPackInstallProperties)
+if(XCODE_VERSION)
+  set(ExternalProject_ARGS -DXCODE_VERSION=${XCODE_VERSION})
+endif()
 add_RunCMake_test(ExternalProject)
 add_RunCMake_test(FetchContent)
 set(CTestCommandLine_ARGS -DPYTHON_EXECUTABLE=${PYTHON_EXECUTABLE})

Tests/RunCMake/ExternalProject/Add_StepDependencies.cmake

@@ -1,5 +1,9 @@
 cmake_minimum_required(VERSION ${CMAKE_VERSION})
-cmake_policy(SET CMP0114 OLD) # Test deprecated behavior.
+if(CMAKE_XCODE_BUILD_SYSTEM VERSION_GREATER_EQUAL 12)
+  cmake_policy(SET CMP0114 NEW)
+else()
+  cmake_policy(SET CMP0114 OLD) # Test deprecated behavior.
+endif()
 
 include(ExternalProject)
 

Tests/RunCMake/ExternalProject/Add_StepDependencies_no_target.cmake

@@ -1,5 +1,9 @@
 cmake_minimum_required(VERSION ${CMAKE_VERSION})
-cmake_policy(SET CMP0114 OLD) # Test deprecated behavior.
+if(CMAKE_XCODE_BUILD_SYSTEM VERSION_GREATER_EQUAL 12)
+  cmake_policy(SET CMP0114 NEW)
+else()
+  cmake_policy(SET CMP0114 OLD) # Test deprecated behavior.
+endif()
 
 include(ExternalProject)
 

Tests/RunCMake/ExternalProject/CMakeLists.txt

@@ -1,3 +1,6 @@
 cmake_minimum_required(VERSION ${CMAKE_VERSION})
 project(${RunCMake_TEST} NONE)
+if(CMAKE_XCODE_BUILD_SYSTEM VERSION_GREATER_EQUAL 12 AND NOT RunCMake_TEST STREQUAL "Xcode-CMP0114")
+  cmake_policy(SET CMP0114 NEW)
+endif()
 include(${RunCMake_TEST}.cmake)

Tests/RunCMake/ExternalProject/RunCMakeTest.cmake

@@ -16,8 +16,10 @@ run_cmake(SourceMissing)
 run_cmake(CMAKE_CACHE_ARGS)
 run_cmake(CMAKE_CACHE_DEFAULT_ARGS)
 run_cmake(CMAKE_CACHE_mix)
-run_cmake(NO_DEPENDS-CMP0114-WARN)
-run_cmake(NO_DEPENDS-CMP0114-OLD)
+if(NOT XCODE_VERSION OR XCODE_VERSION VERSION_LESS 12)
+  run_cmake(NO_DEPENDS-CMP0114-WARN)
+  run_cmake(NO_DEPENDS-CMP0114-OLD)
+endif()
 run_cmake(NO_DEPENDS-CMP0114-NEW)
 run_cmake(NO_DEPENDS-CMP0114-NEW-Direct)
 run_cmake(Add_StepDependencies)
@@ -25,6 +27,9 @@ run_cmake(Add_StepDependencies_iface)
 run_cmake(Add_StepDependencies_iface_step)
 run_cmake(Add_StepDependencies_no_target)
 run_cmake(UsesTerminal)
+if(XCODE_VERSION AND XCODE_VERSION VERSION_GREATER_EQUAL 12)
+  run_cmake(Xcode-CMP0114)
+endif()
 
 macro(check_steps_missing proj)
   set(steps "${ARGN}")
@@ -53,7 +58,9 @@ function(run_steps_CMP0114 val)
   run_cmake_command(Steps-CMP0114-${val}-build-install ${CMAKE_COMMAND} --build . --target proj1-install)
   run_cmake_command(Steps-CMP0114-${val}-build-test ${CMAKE_COMMAND} --build . --target proj1-test)
 endfunction()
-run_steps_CMP0114(OLD)
+if(NOT XCODE_VERSION OR XCODE_VERSION VERSION_LESS 12)
+  run_steps_CMP0114(OLD)
+endif()
 run_steps_CMP0114(NEW)
 
 # Run both cmake and build steps. We always do a clean before the

Tests/RunCMake/ExternalProject/Xcode-CMP0114-stderr.txt

@@ -0,0 +1,11 @@
+^CMake Warning \(dev\) at .*/Modules/ExternalProject.cmake:[0-9]+ \(message\):
+  Policy CMP0114 is not set to NEW.  In order to support the Xcode "new build
+  system", this project must be updated to set policy CMP0114 to NEW.
+
+  Since CMake is generating for the Xcode "new build system",
+  ExternalProject_Add will use policy CMP0114's NEW behavior anyway, but the
+  generated build system may not match what the project intends.
+Call Stack \(most recent call first\):
+  Xcode-CMP0114.cmake:[0-9]+ \(ExternalProject_Add\)
+  CMakeLists.txt:[0-9]+ \(include\)
+This warning is for project developers.  Use -Wno-dev to suppress it.$

Tests/RunCMake/ExternalProject/Xcode-CMP0114.cmake

@@ -0,0 +1,2 @@
+include(ExternalProject)
+ExternalProject_Add(MyProj SOURCE_DIR .)