RunCMake.Ninja: add a test for assumed sources

This is a dark corner of the Ninja generator. It should be fixed in the
future, but add a test which shows its behaviors.

Tests/RunCMake/Ninja/AssumedSources.cmake

@@ -0,0 +1,20 @@
+cmake_minimum_required(VERSION 3.8)
+project(AssumedSources)
+
+set_source_files_properties(
+  "${CMAKE_CURRENT_BINARY_DIR}/target.c"
+  "${CMAKE_CURRENT_BINARY_DIR}/target-no-depends.c"
+  PROPERTIES GENERATED 1)
+
+add_executable(working
+  "${CMAKE_CURRENT_BINARY_DIR}/target.c"
+  "${CMAKE_CURRENT_BINARY_DIR}/target-no-depends.c")
+
+add_custom_target(
+  gen-target.c ALL
+  COMMAND "${CMAKE_COMMAND}" -E copy_if_different "${CMAKE_CURRENT_SOURCE_DIR}/dep.c" "${CMAKE_CURRENT_BINARY_DIR}/target.c")
+add_custom_target(
+  gen-target-no-depends.c ALL
+  COMMAND "${CMAKE_COMMAND}" -E copy_if_different "${CMAKE_CURRENT_SOURCE_DIR}/dep.c" "${CMAKE_CURRENT_BINARY_DIR}/target-no-depends.c")
+
+add_dependencies(working gen-target.c)

Tests/RunCMake/Ninja/RunCMakeTest.cmake

@@ -112,6 +112,22 @@ function (run_LooseObjectDepends)
 endfunction ()
 run_LooseObjectDepends()
 
+function (run_AssumedSources)
+  set(RunCMake_TEST_BINARY_DIR ${RunCMake_BINARY_DIR}/AssumedSources-build)
+  run_cmake(AssumedSources)
+  run_ninja("${RunCMake_TEST_BINARY_DIR}" "target.c")
+  if (NOT EXISTS "${RunCMake_TEST_BINARY_DIR}/target.c")
+    message(FATAL_ERROR
+      "Dependencies for an assumed source did not hook up properly for 'target.c'.")
+  endif ()
+  run_ninja("${RunCMake_TEST_BINARY_DIR}" "target-no-depends.c")
+  if (EXISTS "${RunCMake_TEST_BINARY_DIR}/target-no-depends.c")
+    message(FATAL_ERROR
+      "Dependencies for an assumed source were magically hooked up for 'target-no-depends.c'.")
+  endif ()
+endfunction ()
+run_AssumedSources()
+
 function(sleep delay)
   execute_process(
     COMMAND ${CMAKE_COMMAND} -E sleep ${delay}