A more comprehensive model for PoV-Blocks and Candidate receipts (#843)

* encode the candidate statement as only the hash

* refactor CandidateReceipt and CollationInfo

* introduce an abridged candidate receipt type

* erasure coding stores candidate receipt

* store omitted data instead and introduce AvailableData type

* refactor availability-store schema

* tweak schema and APIs a bit more

* get availability-store tests passing

* accept AbridgedCandidateReceipt in `set_heads`

* change statement type in primitives to be hash-only

* fix parachains runtime tests

* fix bad merge

* rewrite validation pipeline

* remove evaluation module

* use abridged candidate hash as canonical

* statement table uses abridged candidate receipts

* kill availability_store::Data struct

* port shared table to new validation pipelines

* extract full validation pipeline to helper

* remove old validation pipeline from collation module

* polkadot-validation compiles

* polkadot-validation tests compile

* make local collation available in validation service

* port legacy network code

* polkadot-network fully ported

* network: ensure fresh statement is propagated

* remove pov_block_hash from LocalValidationData

* remove candidate_hash field from AttestedCandidate and update runtime

* port runtimes to new ParachainHost definition

* port over polkadot-collator

* fix test compilation

* better fix

* remove unrelated validation work dispatch fix

* address grumbles

* fix equality check

polkadot/validation/src/error.rs

@@ -16,7 +16,7 @@
 
 //! Errors that can occur during the validation process.
 
-use polkadot_primitives::parachain::ValidatorId;
+use polkadot_primitives::{parachain::ValidatorId, Hash};
 
 /// Error type for validation
 #[derive(Debug, derive_more::Display, derive_more::From)]
@@ -25,6 +25,12 @@ pub enum Error {
 	Client(sp_blockchain::Error),
 	/// Consensus error
 	Consensus(consensus::error::Error),
+	/// A wasm-validation error.
+	WasmValidation(parachain::wasm_executor::Error),
+	/// An I/O error.
+	Io(std::io::Error),
+	/// An error in the availability erasure-coding.
+	ErasureCoding(polkadot_erasure_coding::Error),
 	#[display(fmt = "Invalid duty roster length: expected {}, got {}", expected, got)]
 	InvalidDutyRosterLength {
 		/// Expected roster length
@@ -48,6 +54,30 @@ pub enum Error {
 	DeadlineComputeFailure(std::time::Duration),
 	#[display(fmt = "Validation service is down.")]
 	ValidationServiceDown,
+	/// PoV-block in collation doesn't match provided.
+	#[display(fmt = "PoV hash mismatch. Expected {:?}, got {:?}", _0, _1)]
+	PoVHashMismatch(Hash, Hash),
+	/// Collator signature is invalid.
+	#[display(fmt = "Invalid collator signature on collation")]
+	InvalidCollatorSignature,
+	/// Head-data too large.
+	#[display(fmt = "Head data size of {} exceeded maximum of {}", _0, _1)]
+	HeadDataTooLarge(usize, usize),
+	/// Head-data mismatch after validation.
+	#[display(fmt = "Validation produced a different parachain header")]
+	HeadDataMismatch,
+	/// Relay parent of candidate not allowed.
+	#[display(fmt = "Relay parent {} of candidate not allowed in this context.", _0)]
+	DisallowedRelayParent(Hash),
+	/// Commitments in candidate match commitments produced by validation.
+	#[display(fmt = "Commitments in candidate receipt do not match those produced by validation")]
+	CommitmentsMismatch,
+	/// The parachain for which validation work is being done is not active.
+	#[display(fmt = "Parachain {:?} is not active", _0)]
+	InactiveParachain(polkadot_primitives::parachain::Id),
+	/// Block data is too big
+	#[display(fmt = "Block data is too big (maximum allowed size: {}, actual size: {})", size, max_size)]
+	BlockDataTooBig { size: u64, max_size: u64 },
 	Join(tokio::task::JoinError)
 }
 
@@ -56,6 +86,9 @@ impl std::error::Error for Error {
 		match self {
 			Error::Client(ref err) => Some(err),
 			Error::Consensus(ref err) => Some(err),
+			Error::WasmValidation(ref err) => Some(err),
+			Error::ErasureCoding(ref err) => Some(err),
+			Error::Io(ref err) => Some(err),
 			_ => None,
 		}
 	}