Serde Bytes unable to serialize / deserialize

I've decided to try out serde for network packet serialization, but it's a pain.

I've been unable to serialize an Enum at all, and I keep getting errors. I can't find a working example online either, there are none in the doc nor in the repo.

That's why I'm looking for :

use serde::{Serialize, Deserialize};

use super::{ClientMessage, ServerMessage};

/// The different messages that can be sent from the client to the lobby.
#[derive(Debug, Serialize, Deserialize)]
pub enum ClientToLobbyMessage {
    Quit,
    CreateRoom,
    JoinRoom(RoomId),
}

impl ClientMessage for ClientToLobbyMessage {
    fn from_bytes(bytes: &[u8]) -> Option<ClientToLobbyMessage> {
        serde_bytes::deserialize(bytes).ok()
    }
}

This gives a compile-time error : the trait bound ClientToLobbyMessage: serde_bytes::Deserialize<'_> is not satisfied.

Adding the the #[serde(with = "serde_bytes")] above the enum fields won't work either:

use serde::{Serialize, Deserialize};

use super::{ClientMessage, ServerMessage};

/// The different messages that can be sent from the client to the lobby.
#[derive(Debug, Serialize, Deserialize)]
pub enum ClientToLobbyMessage {
    #[serde(with = "serde_bytes")]
    Quit,
    #[serde(with = "serde_bytes")]
    CreateRoom,
    #[serde(with = "serde_bytes")]
    JoinRoom(RoomId),
}

This gives an error on the derive macros: this function takes 2 arguments but 1 argument was supplied on the Serialize, and the trait bound (): serde_bytes::Deserialize<'_> is not satisfied for the Deserialize.

Finally, I can't find derive macros in the serde_bytes package, as use serde_bytes::{Serialize, Deserialize}; states : Serialize is imported here, but it is only a trait, without a derive macro.

The Cargo.toml file looks like :

[dependencies]
serde = { version = "1.0.178", features = ["derive"] }
serde_bytes = "0.11.12"

And any try to add features to serde_bytes like I did with serde resulted in: failed to select a version for serde_bytes which could resolve this conflict error.

I really hope I'm missing something obvious here, but I'm kinda desappointed as I heard that serde was super easy to use.

Solution

As your example is incomplete, I will assume your example is:

use serde::{Deserialize, Serialize};

trait ClientMessage: Sized {
    fn from_bytes(bytes: &[u8]) -> Option<Self>;
}

/// The different messages that can be sent from the client to the lobby.
#[derive(Debug, Serialize, Deserialize)]
pub enum ClientToLobbyMessage {
    Quit,
    CreateRoom,
    JoinRoom(i32),
}

impl ClientMessage for ClientToLobbyMessage {
    fn from_bytes(bytes: &[u8]) -> Option<ClientToLobbyMessage> {
        serde_bytes::deserialize(bytes).ok()
    }
}

Which produces this monstrousity of an error message:

error[E0277]: the trait bound `&[u8]: Deserializer<'_>` is not satisfied
   --> src\lib.rs:17:34
    |
17  |         serde_bytes::deserialize(bytes).ok()
    |         ------------------------ ^^^^^ the trait `Deserializer<'_>` is not implemented for `&[u8]`
    |         |
    |         required by a bound introduced by this call
    |
    = help: the following other types implement trait `Deserializer<'de>`:
              UnitDeserializer<E>
              U32Deserializer<E>
              _::_serde::de::value::StrDeserializer<'a, E>
              _::_serde::de::value::BorrowedStrDeserializer<'de, E>
              StringDeserializer<E>
              CowStrDeserializer<'a, E>
              BytesDeserializer<'a, E>
              BorrowedBytesDeserializer<'de, E>
            and 25 others
note: required by a bound in `serde_bytes::deserialize`
   --> C:\Users\Finomnis\.cargo\registry\src\index.crates.io-6f17d22bba15001f\serde_bytes-0.11.12\src\lib.rs:110:8
    |
107 | pub fn deserialize<'de, T, D>(deserializer: D) -> Result<T, D::Error>
    |        ----------- required by a bound in this function
...
110 |     D: Deserializer<'de>,
    |        ^^^^^^^^^^^^^^^^^ required by this bound in `deserialize`

error[E0277]: the trait bound `&[u8]: Deserializer<'_>` is not satisfied
  --> src\lib.rs:17:9
   |
17 |         serde_bytes::deserialize(bytes).ok()
   |         ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Deserializer<'_>` is not implemented for `&[u8]`
   |
   = help: the following other types implement trait `Deserializer<'de>`:
             UnitDeserializer<E>
             U32Deserializer<E>
             _::_serde::de::value::StrDeserializer<'a, E>
             _::_serde::de::value::BorrowedStrDeserializer<'de, E>
             StringDeserializer<E>
             CowStrDeserializer<'a, E>
             BytesDeserializer<'a, E>
             BorrowedBytesDeserializer<'de, E>
           and 25 others

error[E0277]: the trait bound `ClientToLobbyMessage: serde_bytes::Deserialize<'_>` is not satisfied
   --> src\lib.rs:17:9
    |
17  |         serde_bytes::deserialize(bytes).ok()
    |         ^^^^^^^^^^^^^^^^^^^^^^^^ the trait `serde_bytes::Deserialize<'_>` is not implemented for `ClientToLobbyMessage`
    |
    = help: the following other types implement trait `serde_bytes::Deserialize<'de>`:
              Box<serde_bytes::Bytes>
              Box<[u8]>
              serde_bytes::ByteBuf
              Cow<'a, [u8]>
              Cow<'a, serde_bytes::Bytes>
              Vec<u8>
              std::option::Option<T>
              &'a [u8]
              &'a serde_bytes::Bytes
note: required by a bound in `serde_bytes::deserialize`
   --> C:\Users\Finomnis\.cargo\registry\src\index.crates.io-6f17d22bba15001f\serde_bytes-0.11.12\src\lib.rs:109:8
    |
107 | pub fn deserialize<'de, T, D>(deserializer: D) -> Result<T, D::Error>
    |        ----------- required by a bound in this function
108 | where
109 |     T: Deserialize<'de>,
    |        ^^^^^^^^^^^^^^^^ required by this bound in `deserialize`

error[E0277]: the trait bound `&[u8]: Deserializer<'_>` is not satisfied
  --> src\lib.rs:17:9
   |
17 |         serde_bytes::deserialize(bytes).ok()
   |         ^^^^^^^^^^^^^^^^^^^^^^^^ the trait `Deserializer<'_>` is not implemented for `&[u8]`
   |
   = help: the following other types implement trait `Deserializer<'de>`:
             UnitDeserializer<E>
             U32Deserializer<E>
             _::_serde::de::value::StrDeserializer<'a, E>
             _::_serde::de::value::BorrowedStrDeserializer<'de, E>
             StringDeserializer<E>
             CowStrDeserializer<'a, E>
             BytesDeserializer<'a, E>
             BorrowedBytesDeserializer<'de, E>
           and 25 others

Your mistake is that you use serde_bytes as if it were a data format, which it is not. It seems to be a helper library for serde for handling byte array types.

As suggested by @kmdreko, you could use the bincode format instead. This one is an actual encoding.

Like this:

use serde::{Deserialize, Serialize};

trait ClientMessage: Sized {
    fn from_bytes(bytes: &[u8]) -> Option<Self>;
}

/// The different messages that can be sent from the client to the lobby.
#[derive(Debug, Serialize, Deserialize)]
pub enum ClientToLobbyMessage {
    Quit,
    CreateRoom,
    JoinRoom(i32),
}

impl ClientMessage for ClientToLobbyMessage {
    fn from_bytes(bytes: &[u8]) -> Option<ClientToLobbyMessage> {
        bincode::deserialize(bytes).ok()
    }
}