WIP

Signed-off-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

frame/support/src/traits/metadata.rs

@@ -242,6 +242,40 @@ pub trait GetStorageVersion {
 	fn on_chain_storage_version() -> StorageVersion;
 }
 
+pub trait GetStorageVersions {
+	/// Returns the current storage version as supported by the pallet.
+	fn current_storage_versions() -> Vec<StorageVersion>;
+	/// Returns the on-chain storage version of the pallet as stored in the storage.
+	fn on_chain_storage_versions() -> Vec<StorageVersion>;
+}
+
+impl<T: GetStorageVersion> GetStorageVersions for T {
+	fn current_storage_versions() -> Vec<StorageVersion> {
+		vec![T::current_storage_version()]
+	}
+
+	fn on_chain_storage_versions() -> Vec<StorageVersion> {
+		vec![T::on_chain_storage_version()]
+	}
+}
+
+#[cfg_attr(all(not(feature = "tuples-96"), not(feature = "tuples-128")), impl_for_tuples(64))]
+#[cfg_attr(all(feature = "tuples-96", not(feature = "tuples-128")), impl_for_tuples(96))]
+#[cfg_attr(feature = "tuples-128", impl_for_tuples(128))]
+impl GetStorageVersions for Tuple {
+	fn current_storage_versions() -> Vec<StorageVersion> {
+		let mut res = vec![];
+		for_tuples!( #( res.extend_from_slice(&Tuple::current_storage_versions()); )* );
+		res
+	}
+
+	fn on_chain_storage_versions() -> Vec<StorageVersion> {
+		let mut res = vec![];
+		for_tuples!( #( res.extend_from_slice(&Tuple::on_chain_storage_versions()); )* );
+		res
+	}
+}
+
 #[cfg(test)]
 mod tests {
 	use super::*;