Merge topic 'fix-IS_NEWER_THAN-usage' into release-3.20

b0da671243 FetchContent: Don't update timestamps if files don't change
404cddb7bb ExternalProject: Fix misuse of IS_NEWER_THAN in timestamp checks

Acked-by: Kitware Robot <kwrobot@kitware.com>
Merge-request: !5825

5 files changed, 85 insertions, 0 deletions

diff --git a/Tests/RunCMake/FetchContent/RunCMakeTest.cmake b/Tests/RunCMake/FetchContent/RunCMakeTest.cmake
index 13013fa..d7fd009 100644
--- a/Tests/RunCMake/FetchContent/RunCMakeTest.cmake
+++ b/Tests/RunCMake/FetchContent/RunCMakeTest.cmake
@@ -27,6 +27,36 @@ run_cmake_with_options(ManualSourceDirectoryRelative
   -D "FETCHCONTENT_SOURCE_DIR_WITHPROJECT:STRING=WithProject"
 )
 
+function(run_FetchContent_TimeStamps)
+  set(RunCMake_TEST_BINARY_DIR ${RunCMake_BINARY_DIR}/TimeStamps)
+  file(REMOVE_RECURSE "${RunCMake_TEST_BINARY_DIR}")
+  file(MAKE_DIRECTORY "${RunCMake_TEST_BINARY_DIR}")
+
+  # First run should execute the commands
+  run_cmake(TimeStamps)
+
+  # Ensure that the file checks we use in the TimeStampsRerun-check.cmake script
+  # will not be defeated by file systems with only one second resolution.
+  # The IS_NEWER_THAN check returns TRUE if the timestamps of the two files are
+  # the same, which has been observed where filesystems only have one second
+  # resolution.
+  set(cmpTimeStamp   ${RunCMake_TEST_BINARY_DIR}/cmpTimeStamp.txt)
+  set(checkTimeStamp ${RunCMake_TEST_BINARY_DIR}/cmpTimeStampCheck.txt)
+  file(TOUCH ${cmpTimeStamp})
+  file(TOUCH ${checkTimeStamp})
+  if("${cmpTimeStamp}" IS_NEWER_THAN "${checkTimeStamp}")
+    execute_process(
+      COMMAND ${CMAKE_COMMAND} -E sleep 1.125
+      COMMAND_ERROR_IS_FATAL LAST
+    )
+  endif()
+
+  # Run again with no changes, no commands should re-execute
+  set(RunCMake_TEST_NO_CLEAN 1)
+  run_cmake(TimeStampsRerun)
+endfunction()
+run_FetchContent_TimeStamps()
+
 function(run_FetchContent_DirOverrides)
   set(RunCMake_TEST_BINARY_DIR ${RunCMake_BINARY_DIR}/DirOverrides-build)
   file(REMOVE_RECURSE "${RunCMake_TEST_BINARY_DIR}")
diff --git a/Tests/RunCMake/FetchContent/TimeStamps-stdout.txt b/Tests/RunCMake/FetchContent/TimeStamps-stdout.txt
new file mode 100644
index 0000000..2ba1ff4
--- /dev/null
+++ b/Tests/RunCMake/FetchContent/TimeStamps-stdout.txt
@@ -0,0 +1,2 @@
+.* *download executed
+.* *patch executed
diff --git a/Tests/RunCMake/FetchContent/TimeStamps.cmake b/Tests/RunCMake/FetchContent/TimeStamps.cmake
new file mode 100644
index 0000000..33874f9
--- /dev/null
+++ b/Tests/RunCMake/FetchContent/TimeStamps.cmake
@@ -0,0 +1,14 @@
+include(FetchContent)
+
+# Do nothing for an update because it would result in always re-running the
+# patch step. We want to test that a patch step that only depends on the
+# download step is not re-run unnecessarily.
+FetchContent_Declare(customCommands
+  PREFIX            ${CMAKE_CURRENT_BINARY_DIR}
+  DOWNLOAD_COMMAND  "${CMAKE_COMMAND}" -E echo "download executed"
+  UPDATE_COMMAND    ""
+  PATCH_COMMAND     "${CMAKE_COMMAND}" -E echo "patch executed"
+)
+
+set(FETCHCONTENT_QUIET FALSE)
+FetchContent_MakeAvailable(customCommands)
diff --git a/Tests/RunCMake/FetchContent/TimeStampsRerun-check.cmake b/Tests/RunCMake/FetchContent/TimeStampsRerun-check.cmake
new file mode 100644
index 0000000..c12a5f4
--- /dev/null
+++ b/Tests/RunCMake/FetchContent/TimeStampsRerun-check.cmake
@@ -0,0 +1,38 @@
+set(cmpFile   ${RunCMake_TEST_BINARY_DIR}/cmpTimeStamp.txt)
+set(scriptDir ${RunCMake_TEST_BINARY_DIR}/tmp)
+set(stampDir  ${RunCMake_TEST_BINARY_DIR}/src/customcommands-stamp)
+
+set(errorMessages)
+if(NOT EXISTS "${cmpFile}")
+  list(APPEND errorMessages "  ${cmpFile} is missing")
+else()
+  foreach(script IN ITEMS mkdirs download patch)
+    set(scriptFile "${scriptDir}/customcommands-${script}.cmake")
+    if(NOT EXISTS "${scriptFile}")
+      list(APPEND errorMessages "  ${scriptFile} is missing")
+    elseif(NOT "${cmpFile}" IS_NEWER_THAN "${scriptFile}")
+      list(APPEND errorMessages "  ${scriptFile} was unexectedly updated")
+    endif()
+  endforeach()
+
+  # special case, not a script, has different extension
+  set(repoInfoFile "${scriptDir}/customcommands-download-repoinfo.txt")
+  if(NOT EXISTS "${repoInfoFile}")
+    list(APPEND errorMessages "  ${repoInfoFile} is missing")
+  elseif(NOT "${cmpFile}" IS_NEWER_THAN "${repoInfoFile}")
+    list(APPEND errorMessages "  ${repoInfoFile} was unexectedly updated")
+  endif()
+
+  foreach(step IN ITEMS download patch)
+    set(stampFile "${stampDir}/customcommands-${step}")
+    if(NOT EXISTS "${stampFile}")
+      list(APPEND errorMessages "  ${stampFile} is missing")
+    elseif(NOT "${cmpFile}" IS_NEWER_THAN "${stampFile}")
+      list(APPEND errorMessages "  ${stampFile} was unexectedly updated")
+    endif()
+  endforeach()
+endif()
+
+if(errorMessages)
+  list(JOIN errorMessages "\n" RunCMake_TEST_FAILED)
+endif()
diff --git a/Tests/RunCMake/FetchContent/TimeStampsRerun.cmake b/Tests/RunCMake/FetchContent/TimeStampsRerun.cmake
new file mode 100644
index 0000000..e13667a
--- /dev/null
+++ b/Tests/RunCMake/FetchContent/TimeStampsRerun.cmake
@@ -0,0 +1 @@
+include(${CMAKE_CURRENT_LIST_DIR}/TimeStamps.cmake)