Some error improvements (#1956)

* Use `HeaderChainError` in parachains module

* Use MessageProofError instead of 'static str in some places

* Avoid implementing Into<'static str> for some errors

We avoid deriving `Debug` for the structs that we use in the runtime and
we derive `RuntimeDebug` instead in order to avoid bloating th eruntime
with static strs. But implementing `Into<'static str>` does the same. So
in some places it makes sense to replace `Into<'static str>` with `Debug`.

* Move the messages error definition

Move the messages error definition outside of `mod target`

bridges/modules/parachains/src/lib.rs

@@ -26,7 +26,7 @@
 pub use weights::WeightInfo;
 pub use weights_ext::WeightInfoExt;
 
-use bp_header_chain::HeaderChain;
+use bp_header_chain::{HeaderChain, HeaderChainError};
 use bp_parachains::{parachain_head_storage_key_at_source, ParaInfo, ParaStoredHeaderData};
 use bp_polkadot_core::parachains::{ParaHash, ParaHead, ParaHeadsProof, ParaId};
 use bp_runtime::{Chain, HashOf, HeaderId, HeaderIdOf, Parachain, StorageProofError};
@@ -125,8 +125,8 @@ pub mod pallet {
 		UnknownRelayChainBlock,
 		/// The number of stored relay block is different from what the relayer has provided.
 		InvalidRelayChainBlockNumber,
-		/// Invalid storage proof has been passed.
-		InvalidStorageProof,
+		/// Error generated by a method defined in `bp-header-chain`.
+		HeaderChain(HeaderChainError),
 		/// Given parachain head is unknown.
 		UnknownParaHead,
 		/// The storage proof doesn't contains storage root. So it is invalid for given header.
@@ -430,10 +430,10 @@ pub mod pallet {
 					storage.ensure_no_unused_nodes()
 				},
 			)
-			.and_then(|r| r.map_err(bp_header_chain::HeaderChainError::StorageProof))
+			.and_then(|r| r.map_err(HeaderChainError::StorageProof))
 			.map_err(|e| {
 				log::trace!(target: LOG_TARGET, "Parachain heads storage proof is invalid: {:?}", e);
-				Error::<T, I>::InvalidStorageProof
+				Error::<T, I>::HeaderChain(e)
 			})?;
 
 			Ok(PostDispatchInfo { actual_weight: Some(actual_weight), pays_fee: Pays::Yes })
@@ -1379,7 +1379,9 @@ mod tests {
 			// try to import head#5 of parachain#1 at relay chain block #0
 			assert_noop!(
 				import_parachain_1_head(0, Default::default(), parachains, proof),
-				Error::<TestRuntime>::InvalidStorageProof
+				Error::<TestRuntime>::HeaderChain(HeaderChainError::StorageProof(
+					StorageProofError::StorageRootMismatch
+				))
 			);
 		});
 	}