fix(swarm): better error message for failed DialPeerConditions

Closes #4407.

Pull-Request: #4409.

Cargo.lock

@@ -3197,7 +3197,7 @@ dependencies = [
 
 [[package]]
 name = "libp2p-swarm"
-version = "0.43.3"
+version = "0.43.4"
 dependencies = [
  "async-std",
  "either",

Cargo.toml

@@ -92,7 +92,7 @@ libp2p-relay = { version = "0.16.1", path = "protocols/relay" }
 libp2p-rendezvous = { version = "0.13.0", path = "protocols/rendezvous" }
 libp2p-request-response = { version = "0.25.1", path = "protocols/request-response" }
 libp2p-server = { version = "0.12.2", path = "misc/server" }
-libp2p-swarm = { version = "0.43.3", path = "swarm" }
+libp2p-swarm = { version = "0.43.4", path = "swarm" }
 libp2p-swarm-derive = { version = "0.33.0", path = "swarm-derive" }
 libp2p-swarm-test = { version = "0.2.0", path = "swarm-test" }
 libp2p-tcp = { version = "0.40.0", path = "transports/tcp" }

swarm/CHANGELOG.md

@@ -1,3 +1,10 @@
+## 0.43.4 - unreleased
+
+- Improve error message when `DialPeerCondition` prevents a dial.
+  See [PR 4409].
+
+[PR 4409]: https://github.com/libp2p/rust-libp2p/pull/4409
+
 ## 0.43.3
 
 - Implement `Display` for `ConnectionId`.

swarm/Cargo.toml

@@ -3,7 +3,7 @@ name = "libp2p-swarm"
 edition = "2021"
 rust-version = { workspace = true }
 description = "The libp2p swarm"
-version = "0.43.3"
+version = "0.43.4"
 authors = ["Parity Technologies <admin@parity.io>"]
 license = "MIT"
 repository = "https://github.com/libp2p/rust-libp2p"

swarm/src/lib.rs

@@ -1580,9 +1580,9 @@ impl fmt::Display for DialError {
                 f,
                 "Dial error: tried to dial local peer id at {endpoint:?}."
             ),
-            DialError::DialPeerConditionFalse(c) => {
-                write!(f, "Dial error: condition {c:?} for dialing peer was false.")
-            }
+            DialError::DialPeerConditionFalse(PeerCondition::Disconnected) => write!(f, "Dial error: dial condition was configured to only happen when disconnected (`PeerCondition::Disconnected`), but node is already connected, thus cancelling new dial."),
+            DialError::DialPeerConditionFalse(PeerCondition::NotDialing) => write!(f, "Dial error: dial condition was configured to only happen if there is currently no ongoing dialing attempt (`PeerCondition::NotDialing`), but a dial is in progress, thus cancelling new dial."),
+            DialError::DialPeerConditionFalse(PeerCondition::Always) => unreachable!("Dial peer condition is by definition true."),
             DialError::Aborted => write!(
                 f,
                 "Dial error: Pending connection attempt has been aborted."