make mycelium optional

3 files changed, 33 insertions, 4 deletions

diff --git a/src/transport/mod.rs b/src/transport/mod.rs
index 9d43e5a..d8c6e2b 100644
--- a/src/transport/mod.rs
+++ b/src/transport/mod.rs
@@ -18,6 +18,7 @@ pub(crate) mod firewall;
 pub(crate) mod identity;
 #[cfg(feature = "libp2p")]
 pub(crate) mod libp2p;
+#[cfg(feature = "mycelium")]
 pub(crate) mod mycelium;
 pub(crate) mod paths;
 #[cfg(test)]
@@ -28,6 +29,11 @@ pub(crate) mod tor;
 pub(crate) mod traffic;
 pub(crate) mod wire;
 
+#[cfg(not(any(feature = "mycelium", feature = "libp2p", feature = "tor")))]
+compile_error!(
+    "continuum needs a transport: build with at least one of the mycelium, libp2p and tor features, e.g. `cargo build --features mycelium`"
+);
+
 /// Starts the transport `name` (one of `config::TRANSPORTS`) as `settings` configure
 /// it: its scheme and the transport, or None if `stop` came first (some take a while to
 /// start: a supervised Mycelium daemon, arti). `key`: the node key, which some prove
@@ -39,8 +45,9 @@ pub(crate) async fn start(
     stop: tokio::sync::watch::Receiver<bool>,
 ) -> Result<Option<(&'static str, std::sync::Arc<dyn Transport>)>> {
     use std::sync::Arc;
-    let _ = key;
+    let _ = (key, &stop);
     let started: Option<(&'static str, Arc<dyn Transport>)> = match name {
+        #[cfg(feature = "mycelium")]
         "mycelium" => mycelium::start(settings, stop)
             .await?
             .map(|transport| (mycelium::SCHEME, Arc::new(transport) as Arc<dyn Transport>)),
diff --git a/src/transport/paths.rs b/src/transport/paths.rs
index e8858da..4d0e775 100644
--- a/src/transport/paths.rs
+++ b/src/transport/paths.rs
@@ -1228,7 +1228,7 @@ mod tests {
             Ok(seed.to_owned())
         }
         fn encode(&self, peer: &str, message: &ParsedMessage) -> Result<EncodedMessage> {
-            crate::transport::mycelium::encode_message(peer, message)
+            crate::transport::sim::encode_message(peer, message)
         }
         async fn send_encoded(&self, _message: &EncodedMessage) -> Result<()> {
             Err(anyhow!("broken"))
diff --git a/src/transport/sim.rs b/src/transport/sim.rs
index 500050b..2410bba 100644
--- a/src/transport/sim.rs
+++ b/src/transport/sim.rs
@@ -2,7 +2,8 @@
 //! [`SimTransport`] on a shared [`SimNet`].
 //!
 //! Messages go through the Mycelium wire encoding (`mycelium::encode_message`), so the
-//! codec is exercised as in production. The net delays, loses and duplicates them per
+//! codec is exercised as in production; without the mycelium feature, through the wire
+//! encoding alone, as libp2p and Tor send it. The net delays, loses and duplicates them per
 //! link, from a seeded generator; nodes can be taken down (everything to and from them
 //! is lost) and brought up again; and a test can inject a message as if a node had sent
 //! it, e.g. one that arrives late.
@@ -24,7 +25,8 @@ use bytes::Bytes;
 use tokio::sync::{mpsc, oneshot};
 use tracing::{debug, warn};
 
-use super::mycelium::{decode_message, encode_message};
+#[cfg(feature = "mycelium")]
+pub(crate) use super::mycelium::{decode_message, encode_message};
 use super::{EncodedMessage, MessageHandler, MessageKind, ParsedMessage, Transport};
 use crate::locks::MutexExt;
 use crate::testrand::Rng;
@@ -249,6 +251,26 @@ pub(crate) struct SimTransport {
     inbox: tokio::sync::Mutex<Option<mpsc::UnboundedReceiver<Delivery>>>,
 }
 
+/// Without Mycelium: a message in the wire encoding alone, as libp2p and Tor send it.
+#[cfg(not(feature = "mycelium"))]
+pub(crate) fn encode_message(peer: &str, message: &ParsedMessage) -> Result<EncodedMessage> {
+    let body = super::wire::encode(message)?;
+    Ok(EncodedMessage {
+        peer: peer.to_owned(),
+        address: peer.to_owned(),
+        payload_len: body.len(),
+        body: body.into(),
+        kind: message.kind(),
+        message: None,
+    })
+}
+
+/// The message in a body made by [`encode_message`].
+#[cfg(not(feature = "mycelium"))]
+pub(crate) fn decode_message(body: &[u8]) -> Result<ParsedMessage> {
+    Ok(super::wire::decode(body)?)
+}
+
 #[async_trait]
 impl Transport for SimTransport {
     fn local_id(&self) -> &str {