fix(gossipsub): always honor support_floodsub setting

Previously, we only honored the `support_floodsub` setting when the user did not specify a custom protocol for gossipsub. This patch fixes this and allows users to advertise floodsub even when they use a custom protocol.

Pull-Request: #3837.

protocols/gossipsub/CHANGELOG.md

@@ -1,8 +1,12 @@
 ## 0.44.4 - unreleased
 
 - Deprecate `metrics`, `protocol`, `subscription_filter`, `time_cache` modules to make them private. See [PR 3777].
+- Honor the `gossipsub::Config::support_floodsub` in all cases.
+  Previously, it was ignored when a custom protocol id was set via `gossipsub::Config::protocol_id`.
+  See [PR 3837].
 
 [PR 3777]: https://github.com/libp2p/rust-libp2p/pull/3777
+[PR 3837]: https://github.com/libp2p/rust-libp2p/pull/3837
 
 ## 0.44.3
 

protocols/gossipsub/src/protocol_priv.rs

@@ -57,7 +57,7 @@ impl ProtocolConfig {
     ///
     /// Sets the maximum gossip transmission size.
     pub fn new(gossipsub_config: &Config) -> ProtocolConfig {
-        let protocol_ids = match gossipsub_config.custom_id_version() {
+        let mut protocol_ids = match gossipsub_config.custom_id_version() {
             Some(v) => match v {
                 Version::V1_0 => vec![ProtocolId::new(
                     gossipsub_config.protocol_id(),
@@ -71,24 +71,22 @@ impl ProtocolConfig {
                 )],
             },
             None => {
-                let mut protocol_ids = vec![
+                vec![
                     ProtocolId::new(
                         gossipsub_config.protocol_id(),
                         PeerKind::Gossipsubv1_1,
                         true,
                     ),
                     ProtocolId::new(gossipsub_config.protocol_id(), PeerKind::Gossipsub, true),
-                ];
-
-                // add floodsub support if enabled.
-                if gossipsub_config.support_floodsub() {
-                    protocol_ids.push(ProtocolId::new("", PeerKind::Floodsub, false));
-                }
-
-                protocol_ids
+                ]
             }
         };
 
+        // add floodsub support if enabled.
+        if gossipsub_config.support_floodsub() {
+            protocol_ids.push(ProtocolId::new("", PeerKind::Floodsub, false));
+        }
+
         ProtocolConfig {
             protocol_ids,
             max_transmit_size: gossipsub_config.max_transmit_size(),
@@ -556,8 +554,8 @@ impl Decoder for GossipsubCodec {
 mod tests {
     use super::*;
     use crate::config::Config;
-    use crate::Behaviour;
     use crate::IdentTopic as Topic;
+    use crate::{Behaviour, ConfigBuilder};
     use libp2p_core::identity::Keypair;
     use quickcheck_ext::*;
 
@@ -653,4 +651,24 @@ mod tests {
 
         QuickCheck::new().quickcheck(prop as fn(_) -> _)
     }
+
+    #[test]
+    fn support_floodsub_with_custom_protocol() {
+        let gossipsub_config = ConfigBuilder::default()
+            .protocol_id("/foosub", Version::V1_1)
+            .support_floodsub()
+            .build()
+            .unwrap();
+
+        let protocol_config = ProtocolConfig::new(&gossipsub_config);
+
+        assert_eq!(
+            String::from_utf8_lossy(&protocol_config.protocol_ids[0].protocol_id),
+            "/foosub"
+        );
+        assert_eq!(
+            String::from_utf8_lossy(&protocol_config.protocol_ids[1].protocol_id),
+            "/floodsub/1.0.0"
+        );
+    }
 }