[FRAME] Test for sane genesis default (#3412)

Closes https://github.com/paritytech/polkadot-sdk/issues/2713

---------

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>
Co-authored-by: André Silva <123550+andresilva@users.noreply.github.com>

substrate/frame/babe/src/lib.rs

@@ -323,7 +323,7 @@ pub mod pallet {
 	#[pallet::genesis_config]
 	pub struct GenesisConfig<T: Config> {
 		pub authorities: Vec<(AuthorityId, BabeAuthorityWeight)>,
-		pub epoch_config: Option<BabeEpochConfiguration>,
+		pub epoch_config: BabeEpochConfiguration,
 		#[serde(skip)]
 		pub _config: sp_std::marker::PhantomData<T>,
 	}
@@ -333,9 +333,7 @@ pub mod pallet {
 		fn build(&self) {
 			SegmentIndex::<T>::put(0);
 			Pallet::<T>::initialize_genesis_authorities(&self.authorities);
-			EpochConfig::<T>::put(
-				self.epoch_config.clone().expect("epoch_config must not be None"),
-			);
+			EpochConfig::<T>::put(&self.epoch_config);
 		}
 	}
 

substrate/frame/session/src/lib.rs

@@ -460,27 +460,13 @@ pub mod pallet {
 					);
 					self.keys.iter().map(|x| x.1.clone()).collect()
 				});
-			assert!(
-				!initial_validators_0.is_empty(),
-				"Empty validator set for session 0 in genesis block!"
-			);
 
 			let initial_validators_1 = T::SessionManager::new_session_genesis(1)
 				.unwrap_or_else(|| initial_validators_0.clone());
-			assert!(
-				!initial_validators_1.is_empty(),
-				"Empty validator set for session 1 in genesis block!"
-			);
 
 			let queued_keys: Vec<_> = initial_validators_1
-				.iter()
-				.cloned()
-				.map(|v| {
-					(
-						v.clone(),
-						Pallet::<T>::load_keys(&v).expect("Validator in session 1 missing keys!"),
-					)
-				})
+				.into_iter()
+				.filter_map(|v| Pallet::<T>::load_keys(&v).map(|k| (v, k)))
 				.collect();
 
 			// Tell everyone about the genesis session keys

substrate/frame/support/procedural/src/construct_runtime/expand/config.rs

@@ -99,6 +99,17 @@ pub fn expand_outer_config(
 				<AllPalletsWithSystem as #scrate::traits::OnGenesis>::on_genesis();
 			}
 		}
+
+		/// Test the `Default` derive impl of the `RuntimeGenesisConfig`.
+		#[cfg(test)]
+		#[test]
+		fn test_genesis_config_builds() {
+			#scrate::__private::sp_io::TestExternalities::default().execute_with(|| {
+				<RuntimeGenesisConfig as #scrate::traits::BuildGenesisConfig>::build(
+					&RuntimeGenesisConfig::default()
+				);
+			});
+		}
 	}
 }
 

substrate/frame/support/src/lib.rs

@@ -780,7 +780,7 @@ macro_rules! assert_err_with_weight {
 			$crate::assert_err!($call.map(|_| ()).map_err(|e| e.error), $err);
 			assert_eq!(dispatch_err_with_post.post_info.actual_weight, $weight);
 		} else {
-			panic!("expected Err(_), got Ok(_).")
+			::core::panic!("expected Err(_), got Ok(_).")
 		}
 	};
 }