[build] cmake: Include our own copy of protobuf_generate to use with plugin (#6989)

The hacks we needed to do to get the existing commands required cmake 3.28. We didn't want that, so just make a local slimmed down copy of the function just for our use. Even better, its much simpler in what it does, no weird hacks.

cmake/modules/WpiProtobuf.cmake

@@ -0,0 +1,92 @@
+function(wpi_protobuf_generate)
+    set(_singleargs PROTOC_OUT_DIR PLUGIN DEPENDENCIES)
+    if(COMMAND target_sources)
+        list(APPEND _singleargs TARGET)
+    endif()
+    set(_multiargs PROTOS)
+
+    cmake_parse_arguments(
+        wpi_protobuf_generate
+        "${_options}"
+        "${_singleargs}"
+        "${_multiargs}"
+        "${ARGN}"
+    )
+
+    if(NOT wpi_protobuf_generate_PROTOS)
+        message(SEND_ERROR "Error: protobuf_generate called without any targets or source files")
+        return()
+    endif()
+
+    if(NOT wpi_protobuf_generate_TARGET)
+        message(SEND_ERROR "Error: wpi_protobuf_generate called without a target")
+        return()
+    endif()
+
+    if(NOT wpi_protobuf_generate_PROTOC_OUT_DIR)
+        message(SEND_ERROR "Error: protobuf_generate called without a protoc out directory")
+        return()
+    endif()
+
+    if(NOT wpi_protobuf_generate_PLUGIN)
+        message(SEND_ERROR "Error: wpi_protobuf_generate called without a plugin")
+        return()
+    endif()
+
+    set(_generate_extensions .pb.h .pb.cc)
+
+    # Create an include path for each file specified
+    foreach(_file ${wpi_protobuf_generate_PROTOS})
+        get_filename_component(_abs_file ${_file} ABSOLUTE)
+        get_filename_component(_abs_dir ${_abs_file} DIRECTORY)
+        list(FIND _protobuf_include_path ${_abs_dir} _contains_already)
+        if(${_contains_already} EQUAL -1)
+            list(APPEND _protobuf_include_path -I ${_abs_dir})
+        endif()
+    endforeach()
+
+    set(_generated_srcs_all)
+    foreach(_proto ${wpi_protobuf_generate_PROTOS})
+        get_filename_component(_abs_file ${_proto} ABSOLUTE)
+        get_filename_component(_abs_dir ${_abs_file} DIRECTORY)
+        get_filename_component(_basename ${_proto} NAME_WLE)
+        file(RELATIVE_PATH _rel_dir ${CMAKE_CURRENT_SOURCE_DIR} ${_abs_dir})
+
+        set(_possible_rel_dir)
+
+        set(_generated_srcs)
+        foreach(_ext ${_generate_extensions})
+            list(
+                APPEND
+                _generated_srcs
+                "${wpi_protobuf_generate_PROTOC_OUT_DIR}/${_possible_rel_dir}${_basename}${_ext}"
+            )
+        endforeach()
+
+        list(APPEND _generated_srcs_all ${_generated_srcs})
+
+        set(_comment "Running WPILib protocol buffer compiler on ${_proto}")
+
+        add_custom_command(
+            OUTPUT ${_generated_srcs}
+            COMMAND protobuf::protoc
+            ARGS
+                --cpp_out ${wpi_protobuf_generate_PROTOC_OUT_DIR} --wpilib_out
+                ${wpi_protobuf_generate_PROTOC_OUT_DIR}
+                --plugin=protoc-gen-wpilib=${wpi_protobuf_generate_PLUGIN} ${_protobuf_include_path}
+                ${_abs_file}
+            DEPENDS
+                ${_abs_file}
+                protobuf::protoc
+                ${wpi_protobuf_generate_DEPENDENCIES}
+                ${wpi_protobuf_generate_PLUGIN}
+            COMMENT ${_comment}
+            VERBATIM
+        )
+    endforeach()
+
+    set_source_files_properties(${_generated_srcs_all} PROPERTIES GENERATED TRUE)
+    if(wpi_protobuf_generate_TARGET)
+        target_sources(${wpi_protobuf_generate_TARGET} PRIVATE ${_generated_srcs_all})
+    endif()
+endfunction()

wpimath/CMakeLists.txt

@@ -4,6 +4,7 @@ include(SubDirList)
 include(CompileWarnings)
 include(AddTest)
 include(DownloadAndCheck)
+include(WpiProtobuf)
 
 # workaround for makefiles - for some reason parent directories aren't created.
 file(MAKE_DIRECTORY "${CMAKE_CURRENT_BINARY_DIR}/protobuf")
@@ -127,15 +128,12 @@ target_link_libraries(protobuf wpiutil)
 
 add_library(wpimath ${wpimath_native_src} $<TARGET_OBJECTS:protobuf>)
 
-protobuf_generate(
-    TARGET protobuf
+wpi_protobuf_generate(
+    TARGET
+    protobuf
     PROTOS ${wpimath_proto_src}
-    PLUGIN "protoc-gen-wpilib=${PROTOC_WPILIB_PLUGIN}"
-    PROTOC_OPTIONS "--cpp_out=${CMAKE_CURRENT_BINARY_DIR}/protobuf" # Needed to generate C++ source
+    PLUGIN ${PROTOC_WPILIB_PLUGIN}
     PROTOC_OUT_DIR "${CMAKE_CURRENT_BINARY_DIR}/protobuf"
-    GENERATE_EXTENSIONS ".pb.h" ".pb.cc" # Enables CMake to add the generated sources to the target
-    LANGUAGE wpilib # Adds a --wpilib_out arg to let our plugin modify the generated protobuf code
-    APPEND_PATH
 )
 
 if(MSVC)