file(GENERATE): Re-run cmake when appropriate.

Re-run if the input file changes or if the output file is removed.

This only works with the Makefile generators currently.  The limitation
of the Ninja generator is tracked as issue #15256.  The IDE
generators will need larger refactoring as they currently rely on
being able to determine the depends and output files at the start of
generate-time, which is too early for the file(GENERATE) case.

4 files changed, 38 insertions, 0 deletions

diff --git a/Tests/RunCMake/File_Generate/ReRunCMake-result.txt b/Tests/RunCMake/File_Generate/ReRunCMake-result.txt
new file mode 100644
index 0000000..573541a
--- /dev/null
+++ b/Tests/RunCMake/File_Generate/ReRunCMake-result.txt
@@ -0,0 +1 @@
+0
diff --git a/Tests/RunCMake/File_Generate/ReRunCMake-stderr.txt b/Tests/RunCMake/File_Generate/ReRunCMake-stderr.txt
new file mode 100644
index 0000000..10f3293
--- /dev/null
+++ b/Tests/RunCMake/File_Generate/ReRunCMake-stderr.txt
@@ -0,0 +1 @@
+^$
diff --git a/Tests/RunCMake/File_Generate/ReRunCMake.cmake b/Tests/RunCMake/File_Generate/ReRunCMake.cmake
new file mode 100644
index 0000000..109d60e
--- /dev/null
+++ b/Tests/RunCMake/File_Generate/ReRunCMake.cmake
@@ -0,0 +1,5 @@
+
+file(GENERATE
+  OUTPUT output_file.txt
+  INPUT "${CMAKE_CURRENT_BINARY_DIR}/input_file.txt"
+)
diff --git a/Tests/RunCMake/File_Generate/RunCMakeTest.cmake b/Tests/RunCMake/File_Generate/RunCMakeTest.cmake
index 7db77d4..97f93d5 100644
--- a/Tests/RunCMake/File_Generate/RunCMakeTest.cmake
+++ b/Tests/RunCMake/File_Generate/RunCMakeTest.cmake
@@ -61,3 +61,34 @@ if (UNIX AND EXISTS /bin/sh)
     message(SEND_ERROR "Generated script did not execute correctly:\n${script_output}\n====\n${script_error}")
   endif()
 endif()
+
+if (RunCMake_GENERATOR MATCHES Makefiles)
+  file(MAKE_DIRECTORY "${RunCMake_BINARY_DIR}/ReRunCMake-build/")
+  file(WRITE "${RunCMake_BINARY_DIR}/ReRunCMake-build/input_file.txt" "InitialContent\n")
+
+  set(RunCMake_TEST_NO_CLEAN ON)
+  run_cmake(ReRunCMake)
+  unset(RunCMake_TEST_NO_CLEAN)
+  file(TIMESTAMP "${RunCMake_BINARY_DIR}/ReRunCMake-build/output_file.txt" timestamp ${timeformat})
+  if(NOT timestamp)
+    message(SEND_ERROR "Could not get timestamp for \"${RunCMake_BINARY_DIR}/ReRunCMake-build/output_file.txt\"")
+  endif()
+
+  execute_process(COMMAND ${CMAKE_COMMAND} -E sleep 1)
+
+  file(WRITE "${RunCMake_BINARY_DIR}/ReRunCMake-build/input_file.txt" "ChangedContent\n")
+  execute_process(COMMAND ${CMAKE_COMMAND} --build "${RunCMake_BINARY_DIR}/ReRunCMake-build/")
+  file(READ "${RunCMake_BINARY_DIR}/ReRunCMake-build/output_file.txt" out_content)
+
+  if(NOT out_content STREQUAL "ChangedContent\n")
+    message(SEND_ERROR "File did not change: \"${RunCMake_BINARY_DIR}/ReRunCMake-build/output_file.txt\"")
+  endif()
+
+
+  file(REMOVE "${RunCMake_BINARY_DIR}/ReRunCMake-build/output_file.txt")
+  execute_process(COMMAND ${CMAKE_COMMAND} --build "${RunCMake_BINARY_DIR}/ReRunCMake-build/")
+
+  if (NOT EXISTS "${RunCMake_BINARY_DIR}/ReRunCMake-build/output_file.txt")
+    message(SEND_ERROR "File did not re-generate: \"${RunCMake_BINARY_DIR}/ReRunCMake-build/output_file.txt\"")
+  endif()
+endif()