cli/net_params: Warn on empty public-addr when starting a validator node

polkadot/prdoc/pr_5240.prdoc

@@ -0,0 +1,12 @@
+title: Warn on empty public-addr when starting a validator node
+
+doc:
+  - audience: Node Operator
+    description: |
+      This PR shows a warning when the `--public-addr` CLI parameter is missing for validators.
+      In the future, we'll transform this warning into a hard failure.
+      Validators are encouraged to provide this parameter for better availability over the network.
+
+crates:
+  - name: sc-cli
+    bump: patch

substrate/client/cli/src/config.rs

@@ -172,7 +172,7 @@ pub trait CliConfiguration<DCV: DefaultConfigurationValues = ()>: Sized {
 		node_key: NodeKeyConfig,
 		default_listen_port: u16,
 	) -> Result<NetworkConfiguration> {
-		Ok(if let Some(network_params) = self.network_params() {
+		let network_config = if let Some(network_params) = self.network_params() {
 			network_params.network_config(
 				chain_spec,
 				is_dev,
@@ -185,7 +185,17 @@ pub trait CliConfiguration<DCV: DefaultConfigurationValues = ()>: Sized {
 			)
 		} else {
 			NetworkConfiguration::new(node_name, client_id, node_key, Some(net_config_dir))
-		})
+		};
+
+		if is_validator && network_config.public_addresses.is_empty() {
+			eprintln!(
+				"WARNING: No public address specified, validator node may not be reachable.
+				Consider setting `--public-addr` to the public IP address of this node.
+				This will become a hard requirement in future versions."
+			);
+		}
+
+		Ok(network_config)
 	}
 
 	/// Get the keystore configuration.