[WIP,cmake] rewire clang format discovery

cmake/modules/DuneXtCommonMacros.cmake

@@ -46,25 +46,25 @@ macro(add_analyze)
     endif(EXISTS ${ANALYZER})
 endmacro(add_analyze)
 
+find_package(ClangFormat 3.7)
 macro(add_format)
-    find_program(FORMAT NAMES clang-format clang-format-3.4 clang-format-3.5 clang-format-3.6 clang-format-3.7 clang-format-3.8 clang-format-3.9)
-    if(EXISTS ${FORMAT})
-        message(STATUS "adding format target")
-	if (NOT TARGET format)
-            add_custom_target( format SOURCES ${ARGN} )
-        endif (NOT TARGET format)
-        foreach(_file ${ARGN})
-            string(REPLACE "/" "_" fn ${_file})
-            if(NOT EXISTS ${_file})
-                # 'fix' relative source defs
-                set(_file ${CMAKE_CURRENT_SOURCE_DIR}/${_file})
-            endif(NOT EXISTS ${_file})
-            add_custom_target("format_${fn}" ${FORMAT} -i -style=file ${_file} )
-            add_dependencies( format "format_${fn}" )
-        endforeach(_file )
-    else()
-        message(WARNING "not adding format target because clang-format is missing")
-    endif(EXISTS ${FORMAT})
+  if(CLANG_FORMAT_FOUND)
+    message(STATUS "adding format target")
+    if (NOT TARGET format)
+      add_custom_target( format SOURCES ${ARGN} )
+    endif (NOT TARGET format)
+    foreach(_file ${ARGN})
+      string(REPLACE "/" "_" fn ${_file})
+      if(NOT EXISTS ${_file})
+          # 'fix' relative source defs
+        set(_file ${CMAKE_CURRENT_SOURCE_DIR}/${_file})
+      endif(NOT EXISTS ${_file})
+      add_custom_target("format_${fn}" ${CLANG_FORMAT_BINARY} -i -style=file ${_file} )
+      add_dependencies( format "format_${fn}" )
+    endforeach(_file )
+  else()
+    message(WARNING "not adding format target because clang-format is missing")
+  endif(CLANG_FORMAT_FOUND)
 endmacro(add_format)
 
 macro(add_forced_doxygen_target)

cmake/modules/FindClangFormat.cmake

+# Use this module by invoking find_package with the form::                                   
+#
+#   find_package(ClangFormat
+#     [version] # Minimum version e.g. 3.7
+#     )                      
+#
+#   optionally pass the minimal version you require like so find_package(ClangFormat 3.7) 
+#   this module set CLANG_FORMAT_EXECUTABLE, CLANG_FORMAT_VERSION
+#   and CLANG_FORMAT_FOUND accordingly
+#
+set(CLANG_FORMAT_FOUND 0)
+find_program(format_binary NAMES clang-format clang-format-3.6 clang-format-3.7 clang-format-3.8 clang-format-3.9 clang-format-4.0)
+if(EXISTS ${format_binary})
+  execute_process(COMMAND ${format_binary} -version OUTPUT_VARIABLE clang_out )
+  message("clang verison out" ${clang_out})
+  string(REGEX REPLACE ".*clang-format version ([0-9]+\\.[0-9]+).*"  "\\1" CLANG_FORMAT_VERSION ${clang_out})
+  set(CLANG_FORMAT_FOUND 1)
+  set(CLANG_FORMAT_EXECUTABLE ${format_binary})
+  if(optional argument passed)
+    check match with CLANG_FORMAT_VERSION
+    if(not matched)
+      message(INFO "Requested clang-format >= arg_passed, found ${CLANG_FORMAT_VERSION}"
+      set(CLANG_FORMAT_FOUND 0)
+    endif()
+  endif()
+  #message("clang-format executable: ${CLANG_FORMAT_EXECUTABLE}")
+  #message("clang-format version: ${CLANG_FORMAT_VERSION}")
+endif()
+