Library: Add compatibility for legacy Tokio 0.2 (#40)

Adds support to the library for tokio 0.2 backward-compatibility. This should hopefully benefit, and prevent lavalink-rs from being blocked on this feature.

These can be reached using, e.g., `gateway-tokio-02`, `driver-tokio-02`, `serenity-rustls-tokio-02`, and `serenity-native-tokio-02` features.

Naturally, this requires some jiggering about with features and the underlying CI, which has been taken care of. Twilight can't be handled in this way, as their last tokio 0.2 version uses the deprecated Discord Gateway v6.

src/ws.rs

@@ -6,14 +6,26 @@
 use crate::model::Event;
 
 use async_trait::async_trait;
+#[cfg(not(feature = "tokio-02-marker"))]
 use async_tungstenite::{
+    self as tungstenite,
+    tokio::ConnectStream,
+    tungstenite::{error::Error as TungsteniteError, protocol::CloseFrame, Message},
+    WebSocketStream,
+};
+#[cfg(feature = "tokio-02-marker")]
+use async_tungstenite_compat::{
+    self as tungstenite,
     tokio::ConnectStream,
     tungstenite::{error::Error as TungsteniteError, protocol::CloseFrame, Message},
     WebSocketStream,
 };
 use futures::{SinkExt, StreamExt, TryStreamExt};
 use serde_json::Error as JsonError;
-use tokio::time::timeout;
+#[cfg(not(feature = "tokio-02-marker"))]
+use tokio::time::{timeout, Duration};
+#[cfg(feature = "tokio-02-marker")]
+use tokio_compat::time::{timeout, Duration};
 use tracing::{instrument, warn};
 
 pub type WsStream = WebSocketStream<ConnectStream>;
@@ -23,7 +35,7 @@ pub type Result<T> = std::result::Result<T, Error>;
 #[derive(Debug)]
 pub enum Error {
     Json(JsonError),
-    #[cfg(all(feature = "rustls", not(feature = "native")))]
+    #[cfg(all(feature = "rustls-marker", not(feature = "native-marker")))]
     Tls(RustlsError),
 
     /// The discord voice gateway does not support or offer zlib compression.
@@ -41,7 +53,7 @@ impl From<JsonError> for Error {
     }
 }
 
-#[cfg(all(feature = "rustls", not(feature = "native")))]
+#[cfg(all(feature = "rustls-marker", not(feature = "native-marker")))]
 impl From<RustlsError> for Error {
     fn from(e: RustlsError) -> Error {
         Error::Tls(e)
@@ -55,7 +67,7 @@ impl From<TungsteniteError> for Error {
 }
 
 use futures::stream::SplitSink;
-#[cfg(all(feature = "rustls", not(feature = "native")))]
+#[cfg(all(feature = "rustls-marker", not(feature = "native-marker")))]
 use std::{
     error::Error as StdError,
     fmt::{Display, Formatter, Result as FmtResult},
@@ -77,7 +89,7 @@ pub trait SenderExt {
 #[async_trait]
 impl ReceiverExt for WsStream {
     async fn recv_json(&mut self) -> Result<Option<Event>> {
-        const TIMEOUT: tokio::time::Duration = tokio::time::Duration::from_millis(500);
+        const TIMEOUT: Duration = Duration::from_millis(500);
 
         let ws_message = match timeout(TIMEOUT, self.next()).await {
             Ok(Some(Ok(v))) => Some(v),
@@ -138,7 +150,7 @@ pub(crate) fn convert_ws_message(message: Option<Message>) -> Result<Option<Even
 /// An error that occured while connecting over rustls
 #[derive(Debug)]
 #[non_exhaustive]
-#[cfg(all(feature = "rustls", not(feature = "native")))]
+#[cfg(all(feature = "rustls-marker", not(feature = "native-marker")))]
 pub enum RustlsError {
     /// An error with the handshake in tungstenite
     HandshakeError,
@@ -146,14 +158,14 @@ pub enum RustlsError {
     Io(IoError),
 }
 
-#[cfg(all(feature = "rustls", not(feature = "native")))]
+#[cfg(all(feature = "rustls-marker", not(feature = "native-marker")))]
 impl From<IoError> for RustlsError {
     fn from(e: IoError) -> Self {
         RustlsError::Io(e)
     }
 }
 
-#[cfg(all(feature = "rustls", not(feature = "native")))]
+#[cfg(all(feature = "rustls-marker", not(feature = "native-marker")))]
 impl Display for RustlsError {
     fn fmt(&self, f: &mut Formatter<'_>) -> FmtResult {
         match self {
@@ -164,7 +176,7 @@ impl Display for RustlsError {
     }
 }
 
-#[cfg(all(feature = "rustls", not(feature = "native")))]
+#[cfg(all(feature = "rustls-marker", not(feature = "native-marker")))]
 impl StdError for RustlsError {
     fn source(&self) -> Option<&(dyn StdError + 'static)> {
         match self {
@@ -174,12 +186,12 @@ impl StdError for RustlsError {
     }
 }
 
-#[cfg(all(feature = "rustls", not(feature = "native")))]
+#[cfg(all(feature = "rustls-marker", not(feature = "native-marker")))]
 #[instrument]
 pub(crate) async fn create_rustls_client(url: Url) -> Result<WsStream> {
-    let (stream, _) = async_tungstenite::tokio::connect_async_with_config::<Url>(
+    let (stream, _) = tungstenite::tokio::connect_async_with_config::<Url>(
         url,
-        Some(async_tungstenite::tungstenite::protocol::WebSocketConfig {
+        Some(tungstenite::tungstenite::protocol::WebSocketConfig {
             max_message_size: None,
             max_frame_size: None,
             max_send_queue: None,
@@ -191,12 +203,12 @@ pub(crate) async fn create_rustls_client(url: Url) -> Result<WsStream> {
     Ok(stream)
 }
 
-#[cfg(feature = "native")]
+#[cfg(feature = "native-marker")]
 #[instrument]
 pub(crate) async fn create_native_tls_client(url: Url) -> Result<WsStream> {
-    let (stream, _) = async_tungstenite::tokio::connect_async_with_config::<Url>(
+    let (stream, _) = tungstenite::tokio::connect_async_with_config::<Url>(
         url,
-        Some(async_tungstenite::tungstenite::protocol::WebSocketConfig {
+        Some(tungstenite::tungstenite::protocol::WebSocketConfig {
             max_message_size: None,
             max_frame_size: None,
             max_send_queue: None,