10997: PROTOBUF_GENERATE_CPP now supports proto files outside current dir

Modules/FindProtobuf.cmake

@@ -73,6 +73,20 @@ function(PROTOBUF_GENERATE_CPP SRCS HDRS)
     return()
   endif(NOT ARGN)
 
+  if(PROTOBUF_GENERATE_CPP_APPEND_PATH)
+    # Create an include path for each file specified
+    foreach(FIL ${ARGN})
+      get_filename_component(ABS_FIL ${FIL} ABSOLUTE)
+      get_filename_component(ABS_PATH ${ABS_FIL} PATH)
+      list(FIND _protobuf_include_path ${ABS_PATH} _contains_already)
+      if(${_contains_already} EQUAL -1)
+          list(APPEND _protobuf_include_path -I ${ABS_PATH})
+      endif()
+    endforeach()
+  else()
+    set(_protobuf_include_path -I ${CMAKE_CURRENT_SOURCE_DIR})
+  endif()
+
   set(${SRCS})
   set(${HDRS})
   foreach(FIL ${ARGN})
@@ -86,7 +100,7 @@ function(PROTOBUF_GENERATE_CPP SRCS HDRS)
       OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/${FIL_WE}.pb.cc"
              "${CMAKE_CURRENT_BINARY_DIR}/${FIL_WE}.pb.h"
       COMMAND  ${PROTOBUF_PROTOC_EXECUTABLE}
-      ARGS --cpp_out  ${CMAKE_CURRENT_BINARY_DIR} --proto_path ${CMAKE_CURRENT_SOURCE_DIR} ${ABS_FIL}
+      ARGS --cpp_out  ${CMAKE_CURRENT_BINARY_DIR} ${_protobuf_include_path} ${ABS_FIL}
       DEPENDS ${ABS_FIL}
       COMMENT "Running C++ protocol buffer compiler on ${FIL}"
       VERBATIM )
@@ -125,11 +139,17 @@ function(_protobuf_find_libraries name filename)
    endif()
 endfunction()
 
-
 #
 # Main.
 #
 
+# By default have PROTOBUF_GENERATE_CPP macro pass -I to protoc
+# for each directory where a proto file is referenced.
+if(NOT DEFINED PROTOBUF_GENERATE_CPP_APPEND_PATH)
+  set(PROTOBUF_GENERATE_CPP_APPEND_PATH TRUE)
+endif()
+
+
 # Google's provided vcproj files generate libraries with a "lib"
 # prefix on Windows
 if(MSVC)