Do not enforce network key presence for collators

Because of https://github.com/paritytech/polkadot-sdk/blob/299aacb56f4f11127b194d12692b00066e91ac92/cumulus/client/cli/src/lib.rs#L318
#3852 wrongly enforces
that the network key is present for collators started with
polkadot-parachain binary, instead of generating it
on the fly.

That is not necessary and created some small friction for
collators, since they have to pass `--unsafe-force-node-key-generation`
or generate the key with the `generate-node-key` command.

This PR fixes that since the change was intended to apply
only for relaychain authorithies.

Signed-off-by: Alexandru Gheorghe <alexandru.gheorghe@parity.io>

polkadot/cli/src/command.rs

@@ -153,6 +153,11 @@ impl SubstrateCli for Cli {
 			},
 		})
 	}
+
+	// Enforce the presence of a network key if the node is started as an authorithy.
+	fn enforce_network_key_exists_when_authority(&self) -> bool {
+		true
+	}
 }
 
 fn set_default_ss58_version(spec: &Box<dyn polkadot_service::ChainSpec>) {

substrate/client/cli/src/config.rs

@@ -437,11 +437,15 @@ pub trait CliConfiguration<DCV: DefaultConfigurationValues = ()>: Sized {
 	///
 	/// By default this is retrieved from `NodeKeyParams` if it is available. Otherwise its
 	/// `NodeKeyConfig::default()`.
-	fn node_key(&self, net_config_dir: &PathBuf) -> Result<NodeKeyConfig> {
+	fn node_key(
+		&self,
+		net_config_dir: &PathBuf,
+		require_key_for_authority: bool,
+	) -> Result<NodeKeyConfig> {
 		let is_dev = self.is_dev()?;
 		let role = self.role(is_dev)?;
 		self.node_key_params()
-			.map(|x| x.node_key(net_config_dir, role, is_dev))
+			.map(|x| x.node_key(net_config_dir, role, is_dev, require_key_for_authority))
 			.unwrap_or_else(|| Ok(Default::default()))
 	}
 
@@ -490,7 +494,8 @@ pub trait CliConfiguration<DCV: DefaultConfigurationValues = ()>: Sized {
 				Database::ParityDb
 			},
 		);
-		let node_key = self.node_key(&net_config_dir)?;
+		let node_key =
+			self.node_key(&net_config_dir, cli.enforce_network_key_exists_when_authority())?;
 		let role = self.role(is_dev)?;
 		let max_runtime_instances = self.max_runtime_instances()?.unwrap_or(8);
 		let is_validator = role.is_authority();

substrate/client/cli/src/lib.rs

@@ -250,4 +250,9 @@ pub trait SubstrateCli: Sized {
 		command.init(&Self::support_url(), &Self::impl_version(), logger_hook, &config)?;
 		Runner::new(config, tokio_runtime, signals)
 	}
+
+	/// Returns if a node should enforce the presence of a node key for authorities.
+	fn enforce_network_key_exists_when_authority(&self) -> bool {
+		false
+	}
 }

substrate/client/cli/src/params/node_key_params.rs

@@ -105,6 +105,7 @@ impl NodeKeyParams {
 		net_config_dir: &PathBuf,
 		role: Role,
 		is_dev: bool,
+		require_key_for_authority: bool,
 	) -> error::Result<NodeKeyConfig> {
 		Ok(match self.node_key_type {
 			NodeKeyType::Ed25519 => {
@@ -116,8 +117,9 @@ impl NodeKeyParams {
 						.clone()
 						.unwrap_or_else(|| net_config_dir.join(NODE_KEY_ED25519_FILE));
 					if !self.unsafe_force_node_key_generation &&
-						role.is_authority() && !is_dev &&
-						!key_path.exists()
+						require_key_for_authority &&
+						role.is_authority() &&
+						!is_dev && !key_path.exists()
 					{
 						return Err(Error::NetworkKeyNotFound(key_path))
 					}
@@ -166,12 +168,14 @@ mod tests {
 					node_key_file: None,
 					unsafe_force_node_key_generation: false,
 				};
-				params.node_key(net_config_dir, Role::Authority, false).and_then(|c| match c {
-					NodeKeyConfig::Ed25519(sc_network::config::Secret::Input(ref ski))
-						if node_key_type == NodeKeyType::Ed25519 && &sk[..] == ski.as_ref() =>
-						Ok(()),
-					_ => Err(error::Error::Input("Unexpected node key config".into())),
-				})
+				params.node_key(net_config_dir, Role::Authority, false, true).and_then(
+					|c| match c {
+						NodeKeyConfig::Ed25519(sc_network::config::Secret::Input(ref ski))
+							if node_key_type == NodeKeyType::Ed25519 && &sk[..] == ski.as_ref() =>
+							Ok(()),
+						_ => Err(error::Error::Input("Unexpected node key config".into())),
+					},
+				)
 			})
 		}
 
@@ -189,7 +193,7 @@ mod tests {
 			};
 
 			let node_key = params
-				.node_key(&PathBuf::from("not-used"), Role::Authority, false)
+				.node_key(&PathBuf::from("not-used"), Role::Authority, false, true)
 				.expect("Creates node key config")
 				.into_keypair()
 				.expect("Creates node key pair");
@@ -238,7 +242,7 @@ mod tests {
 					let dir = PathBuf::from(net_config_dir.clone());
 					let typ = params.node_key_type;
 					let role = role.clone();
-					params.node_key(net_config_dir, role, is_dev).and_then(move |c| match c {
+					params.node_key(net_config_dir, role, is_dev, true).and_then(move |c| match c {
 						NodeKeyConfig::Ed25519(sc_network::config::Secret::File(ref f))
 							if typ == NodeKeyType::Ed25519 &&
 								f == &dir.join(NODE_KEY_ED25519_FILE) =>