feat: make runtime features optional in swarm-test (libp2p#5551)

## Description

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Sometimes a test uses custom swarm building logic and doesn't need `fn
new_ephemeral`, and sometimes a test uses `tokio` runtime other than
`async-std`.
This PR adds the `tokio` runtime support and makes both `async-std` and
`tokio` runtimes optional behind features to make it more flexible.

## Notes & open questions

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## Change checklist

<!-- Please add a Changelog entry in the appropriate crates and bump the
crate versions if needed. See
<https://github.com/libp2p/rust-libp2p/blob/master/docs/release.md#development-between-releases>-->

- [x] I have performed a self-review of my own code
- [x] I have made corresponding changes to the documentation
- [ ] I have added tests that prove my fix is effective or that my
feature works
- [x] A changelog entry has been made in the appropriate crates

---------

Co-authored-by: João Oliveira <hello@jxs.pt>

Cargo.toml

@@ -104,7 +104,7 @@ libp2p-server = { version = "0.12.8", path = "misc/server" }
 libp2p-stream = { version = "0.2.0-alpha", path = "protocols/stream" }
 libp2p-swarm = { version = "0.45.2", path = "swarm" }
 libp2p-swarm-derive = { version = "=0.35.0", path = "swarm-derive" } # `libp2p-swarm-derive` may not be compatible with different `libp2p-swarm` non-breaking releases. E.g. `libp2p-swarm` might introduce a new enum variant `FromSwarm` (which is `#[non-exhaustive]`) in a non-breaking release. Older versions of `libp2p-swarm-derive` would not forward this enum variant within the `NetworkBehaviour` hierarchy. Thus the version pinning is required.
-libp2p-swarm-test = { version = "0.4.0", path = "swarm-test" }
+libp2p-swarm-test = { version = "0.4.1", path = "swarm-test" }
 libp2p-tcp = { version = "0.42.0", path = "transports/tcp" }
 libp2p-tls = { version = "0.5.0", path = "transports/tls" }
 libp2p-uds = { version = "0.41.0", path = "transports/uds" }

swarm-test/CHANGELOG.md

@@ -1,3 +1,10 @@
+## 0.4.1
+
+- Add `tokio` runtime support and make `tokio` and `async-std` runtimes optional behind features.
+  See [PR 5551].
+
+[PR 5551]: https://github.com/libp2p/rust-libp2p/pull/5551
+
 ## 0.4.0
 
 <!-- Update to libp2p-swarm v0.45.0 -->

swarm-test/Cargo.toml

@@ -1,6 +1,6 @@
 [package]
 name = "libp2p-swarm-test"
-version = "0.4.0"
+version = "0.4.1"
 edition = "2021"
 rust-version = { workspace = true }
 license = "MIT"
@@ -16,13 +16,19 @@ async-trait = "0.1.80"
 libp2p-core = { workspace = true }
 libp2p-identity = { workspace = true, features = ["rand"] }
 libp2p-plaintext = { workspace = true }
-libp2p-swarm = { workspace = true, features = ["async-std"] }
-libp2p-tcp = { workspace = true, features = ["async-io"] }
+libp2p-swarm = { workspace = true }
+libp2p-tcp = { workspace = true }
 libp2p-yamux = { workspace = true }
 futures = { workspace = true }
 rand = "0.8.5"
 tracing = { workspace = true }
 futures-timer = "3.0.3"
 
+[features]
+default = ["async-std"]
+
+async-std = ["libp2p-swarm/async-std", "libp2p-tcp/async-io"]
+tokio = ["libp2p-swarm/tokio", "libp2p-tcp/tokio"]
+
 [lints]
 workspace = true

swarm-test/src/lib.rs

@@ -21,14 +21,10 @@
 use async_trait::async_trait;
 use futures::future::{BoxFuture, Either};
 use futures::{FutureExt, StreamExt};
-use libp2p_core::{
-    multiaddr::Protocol, transport::MemoryTransport, upgrade::Version, Multiaddr, Transport,
-};
-use libp2p_identity::{Keypair, PeerId};
-use libp2p_plaintext as plaintext;
+use libp2p_core::{multiaddr::Protocol, Multiaddr};
+use libp2p_identity::PeerId;
 use libp2p_swarm::dial_opts::PeerCondition;
-use libp2p_swarm::{self as swarm, dial_opts::DialOpts, NetworkBehaviour, Swarm, SwarmEvent};
-use libp2p_yamux as yamux;
+use libp2p_swarm::{dial_opts::DialOpts, NetworkBehaviour, Swarm, SwarmEvent};
 use std::fmt::Debug;
 use std::future::IntoFuture;
 use std::time::Duration;
@@ -38,12 +34,23 @@ use std::time::Duration;
 pub trait SwarmExt {
     type NB: NetworkBehaviour;
 
-    /// Create a new [`Swarm`] with an ephemeral identity.
+    /// Create a new [`Swarm`] with an ephemeral identity and the `async-std` runtime.
     ///
-    /// The swarm will use a [`MemoryTransport`] together with a [`plaintext::Config`] authentication layer and
-    /// [`yamux::Config`] as the multiplexer. However, these details should not be relied upon by the test
+    /// The swarm will use a [`libp2p_core::transport::MemoryTransport`] together with a [`libp2p_plaintext::Config`] authentication layer and
+    /// [`libp2p_yamux::Config`] as the multiplexer. However, these details should not be relied upon by the test
     /// and may change at any time.
-    fn new_ephemeral(behaviour_fn: impl FnOnce(Keypair) -> Self::NB) -> Self
+    #[cfg(feature = "async-std")]
+    fn new_ephemeral(behaviour_fn: impl FnOnce(libp2p_identity::Keypair) -> Self::NB) -> Self
+    where
+        Self: Sized;
+
+    /// Create a new [`Swarm`] with an ephemeral identity and the `tokio` runtime.
+    ///
+    /// The swarm will use a [`libp2p_core::transport::MemoryTransport`] together with a [`libp2p_plaintext::Config`] authentication layer and
+    /// [`libp2p_yamux::Config`] as the multiplexer. However, these details should not be relied upon by the test
+    /// and may change at any time.
+    #[cfg(feature = "tokio")]
+    fn new_ephemeral_tokio(behaviour_fn: impl FnOnce(libp2p_identity::Keypair) -> Self::NB) -> Self
     where
         Self: Sized;
 
@@ -200,26 +207,58 @@ where
 {
     type NB = B;
 
-    fn new_ephemeral(behaviour_fn: impl FnOnce(Keypair) -> Self::NB) -> Self
+    #[cfg(feature = "async-std")]
+    fn new_ephemeral(behaviour_fn: impl FnOnce(libp2p_identity::Keypair) -> Self::NB) -> Self
     where
         Self: Sized,
     {
+        use libp2p_core::{transport::MemoryTransport, upgrade::Version, Transport as _};
+        use libp2p_identity::Keypair;
+
         let identity = Keypair::generate_ed25519();
         let peer_id = PeerId::from(identity.public());
 
         let transport = MemoryTransport::default()
             .or_transport(libp2p_tcp::async_io::Transport::default())
             .upgrade(Version::V1)
-            .authenticate(plaintext::Config::new(&identity))
-            .multiplex(yamux::Config::default())
+            .authenticate(libp2p_plaintext::Config::new(&identity))
+            .multiplex(libp2p_yamux::Config::default())
+            .timeout(Duration::from_secs(20))
+            .boxed();
+
+        Swarm::new(
+            transport,
+            behaviour_fn(identity),
+            peer_id,
+            libp2p_swarm::Config::with_async_std_executor()
+                .with_idle_connection_timeout(Duration::from_secs(5)), // Some tests need connections to be kept alive beyond what the individual behaviour configures.,
+        )
+    }
+
+    #[cfg(feature = "tokio")]
+    fn new_ephemeral_tokio(behaviour_fn: impl FnOnce(libp2p_identity::Keypair) -> Self::NB) -> Self
+    where
+        Self: Sized,
+    {
+        use libp2p_core::{transport::MemoryTransport, upgrade::Version, Transport as _};
+        use libp2p_identity::Keypair;
+
+        let identity = Keypair::generate_ed25519();
+        let peer_id = PeerId::from(identity.public());
+
+        let transport = MemoryTransport::default()
+            .or_transport(libp2p_tcp::tokio::Transport::default())
+            .upgrade(Version::V1)
+            .authenticate(libp2p_plaintext::Config::new(&identity))
+            .multiplex(libp2p_yamux::Config::default())
             .timeout(Duration::from_secs(20))
             .boxed();
 
         Swarm::new(
             transport,
             behaviour_fn(identity),
             peer_id,
-            swarm::Config::with_async_std_executor()
+            libp2p_swarm::Config::with_tokio_executor()
                 .with_idle_connection_timeout(Duration::from_secs(5)), // Some tests need connections to be kept alive beyond what the individual behaviour configures.,
         )
     }