feat: replace ProtocolName with AsRef<str>

Previously, a protocol could be any sequence of bytes as long as it started with `/`. Now, we directly parse a protocol as `String` which enforces it to be valid UTF8.

To notify users of this change, we delete the `ProtocolName` trait. The new requirement is that users need to provide a type that implements `AsRef<str>`.

We also add a `StreamProtocol` newtype in `libp2p-swarm` which provides an easy way for users to ensure their protocol strings are compliant. The newtype enforces that protocol strings start with `/`. `StreamProtocol` also implements `AsRef<str>`, meaning users can directly use it in their upgrades.

`multistream-select` by itself only changes marginally with this patch. The only thing we enforce in the type-system is that protocols must implement `AsRef<str>`.

Resolves: #2831.

Pull-Request: #3746.

protocols/rendezvous/src/handler.rs

@@ -20,9 +20,10 @@
 
 use crate::codec;
 use crate::codec::Message;
+use libp2p_swarm::StreamProtocol;
 use void::Void;
 
-const PROTOCOL_IDENT: &[u8] = b"/rendezvous/1.0.0";
+const PROTOCOL_IDENT: StreamProtocol = StreamProtocol::new("/rendezvous/1.0.0");
 
 pub(crate) mod inbound;
 pub(crate) mod outbound;

protocols/rendezvous/src/substream_handler.rs

@@ -31,7 +31,8 @@ use instant::Instant;
 use libp2p_core::{InboundUpgrade, OutboundUpgrade, UpgradeInfo};
 use libp2p_swarm::handler::{ConnectionEvent, FullyNegotiatedInbound, FullyNegotiatedOutbound};
 use libp2p_swarm::{
-    ConnectionHandler, ConnectionHandlerEvent, KeepAlive, NegotiatedSubstream, SubstreamProtocol,
+    ConnectionHandler, ConnectionHandlerEvent, KeepAlive, NegotiatedSubstream, StreamProtocol,
+    SubstreamProtocol,
 };
 use std::collections::{HashMap, VecDeque};
 use std::fmt;
@@ -127,21 +128,21 @@ impl fmt::Display for OutboundSubstreamId {
 }
 
 pub struct PassthroughProtocol {
-    ident: Option<&'static [u8]>,
+    ident: Option<StreamProtocol>,
 }
 
 impl PassthroughProtocol {
-    pub fn new(ident: &'static [u8]) -> Self {
+    pub fn new(ident: StreamProtocol) -> Self {
         Self { ident: Some(ident) }
     }
 }
 
 impl UpgradeInfo for PassthroughProtocol {
-    type Info = &'static [u8];
+    type Info = StreamProtocol;
     type InfoIter = std::option::IntoIter<Self::Info>;
 
     fn protocol_info(&self) -> Self::InfoIter {
-        self.ident.into_iter()
+        self.ident.clone().into_iter()
     }
 }