CMake: copy clang and resource files only if necessary

Uses a timestamp file in the build directory to detect when the input
changes using DEPENDS from add_custom_command.

Total copied files size sum up to more than 260 MB. This was copied at every
incremental build, even if nothing changed.

This leads to faster build, especially when the copied files are not
cached in RAM or when not using a SSD.

Change-Id: I3a0b691b961e1d8591068bacf40ae2467c8637cf
Reviewed-by: Eike Ziller <eike.ziller@qt.io>
Reviewed-by: Cristian Adam <cristian.adam@qt.io>

5 files changed, 64 insertions, 48 deletions

diff --git a/cmake/QtCreatorAPI.cmake b/cmake/QtCreatorAPI.cmake
index d88cff2fc66..4351c897f7c 100644
--- a/cmake/QtCreatorAPI.cmake
+++ b/cmake/QtCreatorAPI.cmake
@@ -1155,3 +1155,49 @@ function(qtc_glob_resources)
   string(APPEND qrcData "</qresource></RCC>")
   file(WRITE "${_arg_QRC_FILE}" "${qrcData}")
 endfunction()
+
+function(qtc_copy_to_builddir custom_target_name)
+  cmake_parse_arguments(_arg "CREATE_SUBDIRS" "DESTINATION" "FILES;DIRECTORIES" ${ARGN})
+  set(timestampFiles)
+
+  qtc_output_binary_dir(_output_binary_dir)
+
+  foreach(srcFile ${_arg_FILES})
+    string(MAKE_C_IDENTIFIER "${srcFile}" destinationTimestampFilePart)
+    set(destinationTimestampFileName "${CMAKE_CURRENT_BINARY_DIR}/.${destinationTimestampFilePart}_timestamp")
+    list(APPEND timestampFiles "${destinationTimestampFileName}")
+
+    add_custom_command(OUTPUT "${destinationTimestampFileName}"
+      COMMAND "${CMAKE_COMMAND}" -E make_directory "${_output_binary_dir}/${_arg_DESTINATION}"
+      COMMAND "${CMAKE_COMMAND}" -E copy "${srcFile}" "${_output_binary_dir}/${_arg_DESTINATION}"
+      COMMAND "${CMAKE_COMMAND}" -E touch "${destinationTimestampFileName}"
+      WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}"
+      COMMENT "Copy ${srcFile} into build directory"
+      DEPENDS "${srcFile}"
+      VERBATIM
+    )
+  endforeach()
+
+  foreach(srcDirectory ${_arg_DIRECTORIES})
+    string(MAKE_C_IDENTIFIER "${srcDirectory}" destinationTimestampFilePart)
+    set(destinationTimestampFileName "${CMAKE_CURRENT_BINARY_DIR}/.${destinationTimestampFilePart}_timestamp")
+    list(APPEND timestampFiles "${destinationTimestampFileName}")
+    set(destinationDirectory "${_output_binary_dir}/${_arg_DESTINATION}")
+
+    if(_arg_CREATE_SUBDIRS)
+      set(destinationDirectory "${destinationDirectory}/${srcDirectory}")
+    endif()
+
+    file(GLOB_RECURSE filesToCopy "${srcDirectory}/*")
+    add_custom_command(OUTPUT "${destinationTimestampFileName}"
+      COMMAND "${CMAKE_COMMAND}" -E copy_directory "${srcDirectory}" "${destinationDirectory}"
+      COMMAND "${CMAKE_COMMAND}" -E touch "${destinationTimestampFileName}"
+      WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}"
+      COMMENT "Copy ${srcDirectory}/ into build directory"
+      DEPENDS ${filesToCopy}
+      VERBATIM
+    )
+  endforeach()
+
+  add_custom_target("${custom_target_name}" ALL DEPENDS ${timestampFiles})
+endfunction()
diff --git a/share/qtcreator/CMakeLists.txt b/share/qtcreator/CMakeLists.txt
index 303fb9c7d0b..622761f4d8a 100644
--- a/share/qtcreator/CMakeLists.txt
+++ b/share/qtcreator/CMakeLists.txt
@@ -20,21 +20,12 @@ if (APPLE)
   set(resource_directories ${resource_directories} scripts)
 endif()
 
-add_custom_target(copy_share_to_builddir ALL
-  COMMENT Copy files into build directory
-  VERBATIM
-)
-
 # copy resource directories during build
-foreach(dir IN ITEMS ${resource_directories})
-  add_custom_command(TARGET copy_share_to_builddir POST_BUILD
-    COMMAND "${CMAKE_COMMAND}" -E copy_directory "${dir}"
-      "${PROJECT_BINARY_DIR}/${IDE_DATA_PATH}/${dir}"
-    WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}"
-    COMMENT Copy resource directories into build directory
-    VERBATIM
-  )
-endforeach()
+qtc_copy_to_builddir(copy_share_to_builddir
+  DIRECTORIES ${resource_directories}
+  DESTINATION "${IDE_DATA_PATH}"
+  CREATE_SUBDIRS
+)
 
 # create install rule for resource directories
 install(DIRECTORY ${resource_directories} DESTINATION "${IDE_DATA_PATH}")
diff --git a/src/libs/3rdparty/syntax-highlighting/CMakeLists.txt b/src/libs/3rdparty/syntax-highlighting/CMakeLists.txt
index 1304c1a004c..ca0a0391060 100644
--- a/src/libs/3rdparty/syntax-highlighting/CMakeLists.txt
+++ b/src/libs/3rdparty/syntax-highlighting/CMakeLists.txt
@@ -37,11 +37,8 @@ install(
   DESTINATION "${IDE_DATA_PATH}/generic-highlighter/"
 )
 
-add_custom_target(copy_generic_highligher_to_builddir ALL VERBATIM)
-add_custom_command(TARGET copy_generic_highligher_to_builddir POST_BUILD
-  COMMAND "${CMAKE_COMMAND}" -E copy_directory data/syntax
-    "${PROJECT_BINARY_DIR}/${IDE_DATA_PATH}/generic-highlighter/syntax"
-  WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}"
-  COMMENT Copy files into build directory
-  VERBATIM
+# copy resource directories during build
+qtc_copy_to_builddir(copy_generic_highligher_to_builddir
+  DIRECTORIES data/syntax
+  DESTINATION "${IDE_DATA_PATH}/generic-highlighter/syntax"
 )
diff --git a/src/libs/clangsupport/CMakeLists.txt b/src/libs/clangsupport/CMakeLists.txt
index 20af2c1b9d2..d1f38507cb9 100644
--- a/src/libs/clangsupport/CMakeLists.txt
+++ b/src/libs/clangsupport/CMakeLists.txt
@@ -147,32 +147,18 @@ if (NOT TARGET libclang)
   return()
 endif()
 
-add_custom_target(copy_clang_to_builddir ALL
-  COMMENT Copy Clang files into build directory
-)
-
 # For the developer build directory
-add_custom_command(TARGET copy_clang_to_builddir POST_BUILD
-  COMMAND "${CMAKE_COMMAND}"
-    -E copy_directory
-      "${LLVM_LIBRARY_DIR}/clang/${CLANG_VERSION}/include"
-      "${PROJECT_BINARY_DIR}/${IDE_LIBEXEC_PATH}/clang/lib/clang/${CLANG_VERSION}/include"
-  VERBATIM
+qtc_copy_to_builddir(copy_clang_to_builddir
+  DIRECTORIES "${LLVM_LIBRARY_DIR}/clang/${CLANG_VERSION}/include"
+  DESTINATION "${IDE_LIBEXEC_PATH}/clang/lib/clang/${CLANG_VERSION}/include"
 )
 
 foreach(executable clang clang-cl clangd clang-tidy clazy-standalone)
   if (EXISTS "${LLVM_TOOLS_BINARY_DIR}/${executable}${CMAKE_EXECUTABLE_SUFFIX}")
-    add_custom_command(TARGET copy_clang_to_builddir PRE_BUILD
-      COMMAND "${CMAKE_COMMAND}"
-        -E make_directory
-          "${PROJECT_BINARY_DIR}/${IDE_LIBEXEC_PATH}/clang/bin/"
-      COMMAND "${CMAKE_COMMAND}"
-        -E copy
-          "${LLVM_TOOLS_BINARY_DIR}/${executable}${CMAKE_EXECUTABLE_SUFFIX}"
-          "${PROJECT_BINARY_DIR}/${IDE_LIBEXEC_PATH}/clang/bin/"
-      VERBATIM
+    qtc_copy_to_builddir(copy_clang_${executable}_to_builddir
+      FILES "${LLVM_TOOLS_BINARY_DIR}/${executable}${CMAKE_EXECUTABLE_SUFFIX}"
+      DESTINATION "${IDE_LIBEXEC_PATH}/clang/bin/"
     )
-
     # For the install directory
     install(PROGRAMS
       "${LLVM_TOOLS_BINARY_DIR}/${executable}${CMAKE_EXECUTABLE_SUFFIX}"
diff --git a/src/share/3rdparty/CMakeLists.txt b/src/share/3rdparty/CMakeLists.txt
index ede2157426e..2168701e06f 100644
--- a/src/share/3rdparty/CMakeLists.txt
+++ b/src/share/3rdparty/CMakeLists.txt
@@ -3,11 +3,7 @@ install(
   DESTINATION "${IDE_DATA_PATH}"
 )
 
-add_custom_target(copy_fonts_to_builddir ALL VERBATIM)
-add_custom_command(TARGET copy_fonts_to_builddir POST_BUILD
-  COMMAND "${CMAKE_COMMAND}" -E copy_directory fonts
-    "${PROJECT_BINARY_DIR}/${IDE_DATA_PATH}/fonts"
-  WORKING_DIRECTORY "${CMAKE_CURRENT_SOURCE_DIR}"
-  COMMENT Copy files into build directory
-  VERBATIM
+qtc_copy_to_builddir(copy_fonts_to_builddir
+	DIRECTORIES fonts
+	DESTINATION "${IDE_DATA_PATH}/fonts"
 )