Include a reference to the validation data in the candidate descriptor (#1442)

* rename GlobalValidationSchedule to GlobalValidationData

* guide: update candidate descriptor to contain validation data hash

* guide: add note in inclusion module about checking validation data hash

* primitives: update CandidateDescriptor to contain new hash

* fix payload computation

* add helpers for computing validation data to runtime modules

* guide: note routines

* inclusion: check validation data hash and fix local_validation_data bug

* add a case to candidate_checks and improve that test substantially

* bump versions

* address review comments

* add a test for including code upgrade

* bump kusama version

* bump westend & polkadot versions

polkadot/runtime/parachains/src/paras.rs

@@ -25,9 +25,9 @@
 
 use sp_std::prelude::*;
 use sp_std::marker::PhantomData;
-use sp_runtime::traits::One;
+use sp_runtime::traits::{One, BlakeTwo256, Hash as HashT, Saturating};
 use primitives::v1::{
-	Id as ParaId, ValidationCode, HeadData,
+	Id as ParaId, ValidationCode, HeadData, LocalValidationData,
 };
 use frame_support::{
 	decl_storage, decl_module, decl_error,
@@ -536,6 +536,37 @@ impl<T: Trait> Module<T> {
 
 		Self::past_code_meta(&id).most_recent_change()
 	}
+
+	/// Compute the local-validation data based on the head of the para. This assumes the
+	/// relay-parent is the parent of the current block.
+	pub(crate) fn local_validation_data(para_id: ParaId) -> Option<LocalValidationData<T::BlockNumber>> {
+		let relay_parent_number = <system::Module<T>>::block_number() - One::one();
+
+		let config = <configuration::Module<T>>::config();
+		let freq = config.validation_upgrade_frequency;
+		let delay = config.validation_upgrade_delay;
+
+		let last_code_upgrade = Self::last_code_upgrade(para_id, true);
+		let can_upgrade_code = last_code_upgrade.map_or(
+			true,
+			|l| { l <= relay_parent_number && relay_parent_number.saturating_sub(l) >= freq },
+		);
+
+		let code_upgrade_allowed = if can_upgrade_code {
+			Some(relay_parent_number + delay)
+		} else {
+			None
+		};
+
+		Some(LocalValidationData {
+			parent_head: Self::para_head(&para_id)?,
+			balance: 0,
+			validation_code_hash: BlakeTwo256::hash_of(
+				&Self::current_code(&para_id)?
+			),
+			code_upgrade_allowed,
+		})
+	}
 }
 
 #[cfg(test)]