Add PalletInfo impl to avid storage collision, fixes tests

Author: ascjones

frame/balances/src/tests_local.rs

@@ -30,6 +30,7 @@ use frame_support::traits::StorageMapShim;
 use frame_support::weights::{Weight, DispatchInfo, IdentityFee};
 use crate::{GenesisConfig, Module, Config, decl_tests, tests::CallWithDispatchInfo};
 use pallet_transaction_payment::CurrencyAdapter;
+use std::any::TypeId;
 
 use frame_system as system;
 impl_outer_origin!{
@@ -47,6 +48,38 @@ impl_outer_event! {
 	}
 }
 
+/// Provides an implementation of `PalletInfo`.
+///
+/// Usually this is generated by the `construct_runtime!` macro, but tests typically use `()`.
+/// However the impl for `()` returns the same prefix "test" for all modules, which causes
+/// collisions between pallets with storage items with the same name. For instance in this case
+/// System and Balances both have a storage item called `Account`.
+pub struct PalletInfo;
+
+impl frame_support::traits::PalletInfo for PalletInfo {
+	fn index<P: 'static>() -> Option<usize> {
+		let type_id = TypeId::of::<P>();
+		if type_id == TypeId::of::<system::Pallet<Test>>() {
+			return Some(0)
+		}
+		if type_id == TypeId::of::<crate::Pallet<Test>>() {
+			return Some(1)
+		}
+		None
+	}
+
+	fn name<P: 'static>() -> Option<&'static str> {
+		let type_id = TypeId::of::<P>();
+		if type_id == TypeId::of::<system::Pallet<Test>>() {
+			return Some("System")
+		}
+		if type_id == TypeId::of::<crate::Pallet<Test>>() {
+			return Some("Balances")
+		}
+		None
+	}
+}
+
 // Workaround for https://github.com/rust-lang/rust/issues/26925 . Remove when sorted.
 #[derive(Clone, PartialEq, Eq, Debug)]
 pub struct Test;
@@ -73,7 +106,7 @@ impl frame_system::Config for Test {
 	type Event = Event;
 	type BlockHashCount = BlockHashCount;
 	type Version = ();
-	type PalletInfo = ();
+	type PalletInfo = PalletInfo;
 	type AccountData = ();
 	type OnNewAccount = ();
 	type OnKilledAccount = ();