add protobuf_generate function, allows use of target_sources where available

cmake/protobuf-config.cmake.in

@@ -7,6 +7,105 @@ include("${CMAKE_CURRENT_LIST_DIR}/protobuf-options.cmake")
 # Imported targets
 include("${CMAKE_CURRENT_LIST_DIR}/protobuf-targets.cmake")
 
+function(protobuf_generate)
+  include(CMakeParseArguments)
+  set(_singleargs LANGUAGE OUT_VAR)
+  if(COMMAND target_sources)
+    list(APPEND _singleargs TARGET)
+  endif()
+
+  cmake_parse_arguments(protobuf_generate "APPEND_PATH" "${_singleargs}" "PROTOS IMPORT_DIRS GENERATE_EXTENSIONS" "${ARGN}")
+
+  if(protobuf_generate_PROTOS AND NOT protobuf_generate_TARGET)
+    message(SEND_ERROR "Error: protobuf_generate called without any targets or source files")
+    return()
+  endif()
+
+  if(NOT protobuf_generate_OUT_VAR AND NOT protobuf_generate_TARGET)
+    message(SEND_ERROR "Error: protobuf_generate called without a target or output variable")
+    return()
+  endif()
+
+  if(NOT protobuf_generate_LANGUAGE)
+    set(protobuf_generate_LANGUAGE cpp)
+  endif()
+  string(TOLOWER ${protobuf_generate_LANGUAGE} protobuf_generate_LANGUAGE)
+
+  if(NOT protobuf_GENERATE_EXTENSIONS)
+    if(protobuf_generate_LANGUAGE STREQUAL cpp)
+      set(protobuf_GENERATE_EXTENSIONS .pb.h .pb.cc)
+    elseif(protobuf_generate_LANGUAGE STREQUAL python)
+      set(protobuf_GENERATE_EXTENSIONS _pb2.py)
+    else()
+      message(SEND_ERROR "Error: protobuf_generate given unknown Language ${LANGUAGE}, please provide a value for GENERATE_EXTENSIONS")
+      return()
+    endif()
+  endif()
+
+  if(protobuf_generate_APPEND_PATH)
+    # Create an include path for each file specified
+    foreach(_file ${ARGN})
+      get_filename_component(_abs_file ${_file} ABSOLUTE)
+      get_filename_component(_abs_path ${_abs_file} 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()
+
+  foreach(DIR ${protobuf_generate_IMPORT_DIRS})
+    get_filename_component(ABS_PATH ${DIR} ABSOLUTE)
+    list(FIND _protobuf_include_path ${ABS_PATH} _contains_already)
+    if(${_contains_already} EQUAL -1)
+        list(APPEND _protobuf_include_path -I ${ABS_PATH})
+    endif()
+  endforeach()
+
+  if(protobuf_generate_TARGET)
+    get_target_property(_source_list ${protobuf_generate_TARGET} SOURCES)
+    foreach(_file ${_source_list})
+      if(_file MATCHES "proto$")
+        list(APPEND protobuf_generate_PROTOS ${_file})
+      endif()
+    endforeach()
+  endif()
+
+  if(NOT protobuf_generate_PROTOS)
+    message(SEND_ERROR "Error: protobuf_generate could not find any .proto files")
+    return()
+  endif()
+
+  set(_generated_srcs)
+  foreach(_proto ${protobuf_generate_PROTOS})
+    get_filename_component(_abs_file ${_proto} ABSOLUTE)
+    get_filename_component(_basename ${_proto} NAME_WE)
+
+    foreach(_ext ${_output_extensions})
+      list(APPEND _generated_srcs "${CMAKE_CURRENT_BINARY_DIR}/${_basename}${_ext}")
+    endforeach()
+
+    add_custom_command(
+      OUTPUT ${_generated_srcs}
+      COMMAND  protobuf::protoc
+      ARGS --${protobuf_generate_LANGUAGE}_out  ${CMAKE_CURRENT_BINARY_DIR} ${_protobuf_include_path} ${_abs_file}
+      DEPENDS ${ABS_FIL} protobuf::protoc
+      COMMENT "Running ${protobuf_generate_LANGUAGE} protocol buffer compiler on ${_proto}"
+      VERBATIM )
+  endforeach()
+
+  set_source_files_properties(${_generated_srcs} PROPERTIES GENERATED TRUE)
+  if(protobuf_generate_OUT_VAR)
+    set(${protobuf_generate_OUT_VAR} ${_generated_srcs} PARENT_SCOPE)
+  endif()
+  if(protobuf_generate_TARGET)
+    target_sources(${protobuf_generate_TARGET} PUBLIC ${_generated_srcs})
+  endif()
+
+endfunction()
+
 # CMake FindProtobuf module compatible file
 if(protobuf_MODULE_COMPATIBLE)
   include("${CMAKE_CURRENT_LIST_DIR}/protobuf-module.cmake")

cmake/protobuf-module.cmake.in

+# This file contains backwards compatibility patches for various legacy functions and variables
 # Functions
 
 function(PROTOBUF_GENERATE_CPP SRCS HDRS)
@@ -7,49 +8,25 @@ function(PROTOBUF_GENERATE_CPP SRCS HDRS)
   endif()
 
   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})
+    set(_append_arg APPEND_PATH)
   endif()
 
   if(DEFINED Protobuf_IMPORT_DIRS)
-    foreach(DIR ${Protobuf_IMPORT_DIRS})
-      get_filename_component(ABS_PATH ${DIR} ABSOLUTE)
-      list(FIND _protobuf_include_path ${ABS_PATH} _contains_already)
-      if(${_contains_already} EQUAL -1)
-          list(APPEND _protobuf_include_path -I ${ABS_PATH})
-      endif()
-    endforeach()
+    set(_import_arg IMPORT_DIRS ${Protobuf_IMPORT_DIRS})
   endif()
 
+  set(_outvar)
+  protobuf_generate(${append_arg} LANGUAGE cpp OUT_VAR _outvar ${_import_arg} PROTOS ${ARGN})
+
   set(${SRCS})
   set(${HDRS})
-  foreach(FIL ${ARGN})
-    get_filename_component(ABS_FIL ${FIL} ABSOLUTE)
-    get_filename_component(FIL_WE ${FIL} NAME_WE)
-
-    list(APPEND ${SRCS} "${CMAKE_CURRENT_BINARY_DIR}/${FIL_WE}.pb.cc")
-    list(APPEND ${HDRS} "${CMAKE_CURRENT_BINARY_DIR}/${FIL_WE}.pb.h")
-
-    add_custom_command(
-      OUTPUT "${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} ${_protobuf_include_path} ${ABS_FIL}
-      DEPENDS ${ABS_FIL} ${Protobuf_PROTOC_EXECUTABLE}
-      COMMENT "Running C++ protocol buffer compiler on ${FIL}"
-      VERBATIM )
+  foreach(_file ${_outvar})
+    if(_file MATCHES "cc$")
+      list(APPEND ${SRCS} ${_file})
+    else()
+      list(APPEND ${HDRS} ${_file})
+    endif()
   endforeach()
-
-  set_source_files_properties(${${SRCS}} ${${HDRS}} PROPERTIES GENERATED TRUE)
   set(${SRCS} ${${SRCS}} PARENT_SCOPE)
   set(${HDRS} ${${HDRS}} PARENT_SCOPE)
 endfunction()
@@ -61,44 +38,16 @@ function(PROTOBUF_GENERATE_PYTHON SRCS)
   endif()
 
   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})
+    set(_append_arg APPEND_PATH)
   endif()
 
   if(DEFINED Protobuf_IMPORT_DIRS)
-    foreach(DIR ${Protobuf_IMPORT_DIRS})
-      get_filename_component(ABS_PATH ${DIR} ABSOLUTE)
-      list(FIND _protobuf_include_path ${ABS_PATH} _contains_already)
-      if(${_contains_already} EQUAL -1)
-          list(APPEND _protobuf_include_path -I ${ABS_PATH})
-      endif()
-    endforeach()
+    set(_import_arg IMPORT_DIRS ${Protobuf_IMPORT_DIRS})
   endif()
 
-  set(${SRCS})
-  foreach(FIL ${ARGN})
-    get_filename_component(ABS_FIL ${FIL} ABSOLUTE)
-    get_filename_component(FIL_WE ${FIL} NAME_WE)
-
-    list(APPEND ${SRCS} "${CMAKE_CURRENT_BINARY_DIR}/${FIL_WE}_pb2.py")
-    add_custom_command(
-      OUTPUT "${CMAKE_CURRENT_BINARY_DIR}/${FIL_WE}_pb2.py"
-      COMMAND  ${Protobuf_PROTOC_EXECUTABLE} --python_out ${CMAKE_CURRENT_BINARY_DIR} ${_protobuf_include_path} ${ABS_FIL}
-      DEPENDS ${ABS_FIL} ${Protobuf_PROTOC_EXECUTABLE}
-      COMMENT "Running Python protocol buffer compiler on ${FIL}"
-      VERBATIM )
-  endforeach()
-
-  set(${SRCS} ${${SRCS}} PARENT_SCOPE)
+  set(_outvar)
+  protobuf_generate(${append_arg} LANGUAGE cpp OUT_VAR _outvar ${_import_arg} PROTOS ${ARGN})
+  set(${SRCS} ${_outvar} PARENT_SCOPE)
 endfunction()
 
 # Environment

examples/CMakeLists.txt

@@ -32,22 +32,6 @@ foreach(example add_person list_people)
   if(protobuf_MODULE_COMPATIBLE) #Legacy Support
     protobuf_generate_cpp(${example}_PROTO_SRCS ${example}_PROTO_HDRS ${${example}_PROTOS})
     list(APPEND ${example}_SRCS ${${example}_PROTO_SRCS} ${${example}_PROTO_HDRS})
-  else()
-
-    foreach(proto_file ${${example}_PROTOS})
-      get_filename_component(proto_file_abs ${proto_file} ABSOLUTE)
-      get_filename_component(basename ${proto_file} NAME_WE)
-      set(generated_files ${basename}.pb.cc ${basename}.pb.h)
-      list(APPEND ${example}_SRCS ${generated_files})
-
-      add_custom_command(
-        OUTPUT ${generated_files}
-        COMMAND protobuf::protoc
-        ARGS --cpp_out ${CMAKE_CURRENT_BINARY_DIR} -I ${CMAKE_CURRENT_SOURCE_DIR} ${proto_file_abs}
-        COMMENT "Generating ${generated_files} from ${proto_file}"
-        VERBATIM
-      )
-    endforeach()
   endif()
 
   #Executable setup
@@ -58,6 +42,7 @@ foreach(example add_person list_people)
     target_link_libraries(${executable_name} ${PROTOBUF_LIBRARIES})
   else()
     target_link_libraries(${executable_name} protobuf::libprotobuf)
+    protobuf_generate(TARGET ${executable_name})
   endif()
 
 endforeach()