Hi!

I'm trying to support serde-based serialization on some Protobuf types I have generated using prost. I do this conditionally by putting the following in the build script for my crate.

fn main() {
    let protos = 
    prost_build::Config::new()
        .type_attribute(".", "#[cfg_attr(feature = \"serde\", derive(serde::Serialize, serde::Deserialize))]");
        .compile_protos(&[/* list of files */], &[/* list of includes */])
        .unwrap();
}

This works great until I use any of the well-known types. The problem, of course, is that the well-known types have already been generated and exist in prost-types. The workaround is to use compile_well_known_types(), like so.

syntax = "proto3";

import "google/protobuf/timestamp.proto";

message LogWithTime {
    string log = 1;
    google.protobuf.Timestamp timestamp = 2;
}

fn main() {
    let protos = 
    prost_build::Config::new()
        .type_attribute(".", "#[cfg_attr(feature = \"serde\", derive(serde::Serialize, serde::Deserialize))]");
        .compile_well_known_types() // <---- added this line!
        .compile_protos(&[/* list of files */], &[/* list of includes */])
        .unwrap();
}

The problem now, however, is that the well-known types I generated are no longer compatible with any other crate's well-known types. So, it becomes difficult to do transformations between the types generated across crates.

My workaround is to generate the well-known types with the appropriate serde attributes in a new shared crate that can be used by all the other crates in my workspace. But, I was wondering: would it be possible to add a feature flag to prost-types that would allow one to turn on support for serde? Or perhaps the feature flag is better situated in prost-build? I'm not sure exactly where the best place to put it is, but generally having support for serde would be nice.