session: add handler for genesis session (#3413)

* session: add handler for genesis session

* node: bump spec version

* aura: handle on_genesis_session

* srml: make sure we don't re-initialize genesis authorities

* session: fix mock

* node: remove genesis authorities from chain spec

* staking: fix mock

* srml: don't initialize genesis authorities twice

* aura: don't reinitialize genesis authorities

* aura: fix runtime_io dependency

* Bump runtime

substrate/srml/session/src/lib.rs

@@ -187,6 +187,12 @@ impl<A> OnSessionEnding<A> for () {
 
 /// Handler for when a session keys set changes.
 pub trait SessionHandler<ValidatorId> {
+	/// The given validator set will be used for the genesis session.
+	/// It is guaranteed that the given validator set will also be used
+	/// for the second session, therefore the first call to `on_new_session`
+	/// should provide the same validator set.
+	fn on_genesis_session<Ks: OpaqueKeys>(validators: &[(ValidatorId, Ks)]);
+
 	/// Session set has changed; act appropriately.
 	fn on_new_session<Ks: OpaqueKeys>(
 		changed: bool,
@@ -203,14 +209,19 @@ pub trait OneSessionHandler<ValidatorId> {
 	/// The key type expected.
 	type Key: Decode + Default + AppKey;
 
+	fn on_genesis_session<'a, I: 'a>(validators: I)
+		where I: Iterator<Item=(&'a ValidatorId, Self::Key)>, ValidatorId: 'a;
+
 	fn on_new_session<'a, I: 'a>(changed: bool, validators: I, queued_validators: I)
 		where I: Iterator<Item=(&'a ValidatorId, Self::Key)>, ValidatorId: 'a;
+
 	fn on_disabled(i: usize);
 }
 
 macro_rules! impl_session_handlers {
 	() => (
 		impl<AId> SessionHandler<AId> for () {
+			fn on_genesis_session<Ks: OpaqueKeys>(_: &[(AId, Ks)]) {}
 			fn on_new_session<Ks: OpaqueKeys>(_: bool, _: &[(AId, Ks)], _: &[(AId, Ks)]) {}
 			fn on_disabled(_: usize) {}
 		}
@@ -218,6 +229,15 @@ macro_rules! impl_session_handlers {
 
 	( $($t:ident)* ) => {
 		impl<AId, $( $t: OneSessionHandler<AId> ),*> SessionHandler<AId> for ( $( $t , )* ) {
+			fn on_genesis_session<Ks: OpaqueKeys>(validators: &[(AId, Ks)]) {
+				$(
+					let our_keys: Box<dyn Iterator<Item=_>> = Box::new(validators.iter()
+						.map(|k| (&k.0, k.1.get::<$t::Key>(<$t::Key as AppKey>::ID)
+							.unwrap_or_default())));
+
+					$t::on_genesis_session(our_keys);
+				)*
+			}
 			fn on_new_session<Ks: OpaqueKeys>(
 				changed: bool,
 				validators: &[(AId, Ks)],
@@ -348,6 +368,9 @@ decl_storage! {
 					))
 					.collect();
 
+				// Tell everyone about the genesis session keys
+				T::SessionHandler::on_genesis_session::<T::Keys>(&queued_keys);
+
 				<Validators<T>>::put(initial_validators);
 				<QueuedKeys<T>>::put(queued_keys);
 			});

substrate/srml/session/src/mock.rs

@@ -62,6 +62,7 @@ impl ShouldEndSession<u64> for TestShouldEndSession {
 
 pub struct TestSessionHandler;
 impl SessionHandler<u64> for TestSessionHandler {
+	fn on_genesis_session<T: OpaqueKeys>(_validators: &[(u64, T)]) {}
 	fn on_new_session<T: OpaqueKeys>(
 		changed: bool,
 		validators: &[(u64, T)],