Tests: add a check for the Swift compiler

This ensures that the tests only run when the Swift compiler is present.

Tests/CMakeLists.txt

@@ -22,6 +22,7 @@ macro(ADD_TEST_MACRO NAME)
 endmacro()
 
 include(${CMAKE_CURRENT_SOURCE_DIR}/CheckFortran.cmake)
+include(${CMAKE_CURRENT_SOURCE_DIR}/CheckSwift.cmake)
 
 # Fake a user home directory to avoid polluting the real one.
 if(DEFINED ENV{HOME} AND NOT CTEST_NO_TEST_HOME)
@@ -365,11 +366,16 @@ if(BUILD_TESTING)
        ((NOT CMAKE_OSX_SDKPRODUCT STREQUAL "Mac OS X") OR
         (NOT CMAKE_OSX_SDKVERSION VERSION_LESS 10.10)))
       if(CMAKE_GENERATOR STREQUAL "Xcode")
-        ADD_TEST_MACRO(SwiftMix SwiftMix)
-        ADD_TEST_MACRO(SwiftOnly SwiftOnly)
+        set(CMake_TEST_XCODE_SWIFT 1)
       endif()
     endif()
   endif()
+  if(CMAKE_Swift_COMPILER OR CMake_TEST_XCODE_SWIFT)
+    ADD_TEST_MACRO(SwiftOnly SwiftOnly)
+    if(CMake_TEST_XCODE_SWIFT)
+      ADD_TEST_MACRO(SwiftMix SwiftMix)
+    endif()
+  endif()
   if(CMAKE_Fortran_COMPILER)
     ADD_TEST_MACRO(FortranOnly FortranOnly)
   endif()

Tests/CheckSwift.cmake

@@ -0,0 +1,61 @@
+if(NOT CMAKE_GENERATOR MATCHES "Xcode|Ninja")
+  set(CMAKE_Swift_COMPILER "")
+  return()
+endif()
+
+if(NOT DEFINED CMAKE_Swift_COMPILER)
+  set(_desc "Looking for a Swift compiler")
+  message(STATUS ${_desc})
+
+  file(REMOVE_RECURSE ${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles/CheckSwift)
+
+  file(WRITE "${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles/CheckSwift/CMakeLists.txt"
+  "cmake_minimum_required(VERSION 3.14)
+project(CheckSwift Swift)
+file(WRITE \"\${CMAKE_CURRENT_BINARY_DIR}/result.cmake\"
+  \"set(CMAKE_Swift_COMPILER \\\"\${CMAKE_Swift_COMPILER}\\\")\\n\"
+  \"set(CMAKE_Swift_FLAGS \\\"\${CMAKE_Swift_FLAGS}\\\")\\n\")
+")
+
+  if(CMAKE_GENERATOR_INSTANCE)
+    set(_D_CMAKE_GENERATOR_INSTANCE "-DCMAKE_GENERATOR_INSTANCE:INTERNAL=${CMAKE_GENERATOR_INSTANCE}")
+  else()
+    set(_D_CMAKE_GENERATOR_INSTANCE "")
+  endif()
+
+  execute_process(WORKING_DIRECTORY
+                    ${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles/CheckSwift
+                  COMMAND
+                    ${CMAKE_COMMAND} . -G ${CMAKE_GENERATOR}
+                                       -A "${CMAKE_GENERATOR_PLATFORM}"
+                                       -T "${CMAKE_GENERATOR_TOOLSET}"
+                                       ${_D_CMAKE_GENERATOR_INSTANCE}
+                  TIMEOUT
+                    60
+                  OUTPUT_VARIABLE
+                    output
+                  ERROR_VARIABLE
+                    output
+                  RESULT_VARIABLE
+                    result)
+
+  include(${CMAKE_CURRENT_BINARY_DIR}/CMakeFiles/CheckSwift/result.cmake
+    OPTIONAL)
+  if(CMAKE_Swift_COMPILER AND "${result}" STREQUAL "0")
+    file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeOutput.log
+      "${_desc} passed with the following output:\n"
+      "${output}\n")
+  else()
+    file(APPEND ${CMAKE_BINARY_DIR}${CMAKE_FILES_DIRECTORY}/CMakeError.log
+      "${_desc} failed with the following output:\n"
+      "${output}\n")
+  endif()
+
+  message(STATUS "${_desc} - ${CMAKE_Swift_COMPILER}")
+
+  set(CMAKE_Swift_COMPILER "${CMAKE_Swift_COMPILER}" CACHE FILEPATH "Swift compiler")
+  set(CMAKE_Swift_FLAGS "${CMAKE_Swift_FLAGS}" CACHE STRING "Swift flags")
+
+  mark_as_advanced(CMAKE_Swift_COMPILER)
+  mark_as_advanced(CMAKE_Swift_FLAGS)
+endif()

Tests/RunCMake/CMakeLists.txt

@@ -205,7 +205,7 @@ if(UNIX AND CMAKE_SHARED_LIBRARY_RUNTIME_C_FLAG AND CMAKE_EXECUTABLE_FORMAT STRE
   add_RunCMake_test(RuntimePath)
 endif()
 add_RunCMake_test(ScriptMode)
-add_RunCMake_test(Swift)
+add_RunCMake_test(Swift -DCMAKE_Swift_COMPILER=${CMAKE_Swift_COMPILER})
 add_RunCMake_test(TargetObjects)
 add_RunCMake_test(TargetSources)
 add_RunCMake_test(ToolchainFile)

Tests/RunCMake/Swift/RunCMakeTest.cmake

@@ -4,6 +4,10 @@ if(RunCMake_GENERATOR STREQUAL Xcode)
   if(XCODE_BELOW_6_1)
     run_cmake(XcodeTooOld)
   endif()
+elseif(RunCMake_GENERATOR STREQUAL Ninja)
+  if(CMAKE_Swift_COMPILER)
+    # Add Ninja-specific Swift tests here.
+  endif()
 else()
   run_cmake(NotSupported)
 endif()