fix(libp2p): expose builder phase error

May close #4829 and #4824.
Export three error types `BehaviourError`, `TransportError`, `WebsocketError` with rename. Feature gated `WebsocketError`.
Exported at crate root as [suggested](#4824 (comment)).

Pull-Request: #5726.

libp2p/CHANGELOG.md

@@ -3,6 +3,9 @@
 - Deprecate `void` crate.
   See [PR 5676](https://github.com/libp2p/rust-libp2p/pull/5676).
 
+- Expose swarm builder phase errors.
+  See [PR 5726](https://github.com/libp2p/rust-libp2p/pull/5726).
+
 ## 0.54.1
 
 - Update individual crates.

libp2p/src/builder.rs

@@ -4,6 +4,10 @@ mod phase;
 mod select_muxer;
 mod select_security;
 
+#[cfg(all(not(target_arch = "wasm32"), feature = "websocket"))]
+pub use phase::WebsocketError;
+pub use phase::{BehaviourError, TransportError};
+
 /// Build a [`Swarm`](libp2p_swarm::Swarm) by combining an identity, a set of
 /// [`Transport`](libp2p_core::Transport)s and a
 /// [`NetworkBehaviour`](libp2p_swarm::NetworkBehaviour).

libp2p/src/builder/phase.rs

@@ -29,6 +29,11 @@ use swarm::*;
 use tcp::*;
 use websocket::*;
 
+pub use behaviour::BehaviourError;
+pub use other_transport::TransportError;
+#[cfg(all(not(target_arch = "wasm32"), feature = "websocket"))]
+pub use websocket::WebsocketError;
+
 use super::{
     select_muxer::SelectMuxerUpgrade, select_security::SelectSecurityUpgrade, SwarmBuilder,
 };

libp2p/src/lib.rs

@@ -148,12 +148,17 @@ pub mod bandwidth;
 #[cfg(doc)]
 pub mod tutorials;
 
+#[cfg(all(not(target_arch = "wasm32"), feature = "websocket"))]
+pub use builder::WebsocketError as WebsocketBuilderError;
 pub use libp2p_identity as identity;
 pub use libp2p_identity::PeerId;
 pub use libp2p_swarm::{Stream, StreamProtocol};
 
 pub use self::{
-    builder::SwarmBuilder,
+    builder::{
+        BehaviourError as BehaviourBuilderError, SwarmBuilder,
+        TransportError as TransportBuilderError,
+    },
     core::{
         transport::TransportError,
         upgrade::{InboundUpgrade, OutboundUpgrade},