Allow runtime to return transaction validation error codes (#1534)

* Allow runtime to return more detailed transaction validation errors.

* Re-use ApplyError codes and update test-runtime.

* Fix pool tests.

* Revert using Compact for validity.

substrate/core/transaction-pool/graph/src/error.rs

@@ -24,14 +24,14 @@ use error_chain::{
 error_chain! {
 	errors {
 		/// Transaction is not verifiable yet, but might be in the future.
-		UnknownTransactionValidity {
+		UnknownTransactionValidity(e: i8) {
 			description("Runtime cannot determine validity of the transaction yet."),
-			display("Unkown Transaction Validity"),
+			display("Unkown Transaction Validity. Error code: {}", e),
 		}
 		/// Transaction is invalid
-		InvalidTransaction {
+		InvalidTransaction(e: i8) {
 			description("Runtime check for the transaction failed."),
-			display("Invalid Transaction"),
+			display("Invalid Transaction. Error Code: {}", e),
 		}
 		/// The transaction is temporarily baned
 		TemporarilyBanned {

substrate/core/transaction-pool/graph/src/pool.rs

@@ -118,12 +118,12 @@ impl<B: ChainApi> Pool<B> {
 							valid_till: block_number.as_().saturating_add(longevity),
 						})
 					},
-					TransactionValidity::Invalid => {
-						bail!(error::Error::from(error::ErrorKind::InvalidTransaction))
+					TransactionValidity::Invalid(e) => {
+						bail!(error::Error::from(error::ErrorKind::InvalidTransaction(e)))
 					},
-					TransactionValidity::Unknown => {
+					TransactionValidity::Unknown(e) => {
 						self.listener.write().invalid(&hash);
-						bail!(error::Error::from(error::ErrorKind::UnknownTransactionValidity))
+						bail!(error::Error::from(error::ErrorKind::UnknownTransactionValidity(e)))
 					},
 				}
 			})
@@ -247,7 +247,7 @@ impl<B: ChainApi> Pool<B> {
 		// Collect the hashes of transactions that now became invalid (meaning that they are succesfuly pruned).
 		let hashes = results.into_iter().enumerate().filter_map(|(idx, r)| match r.map_err(error::IntoPoolError::into_pool_error) {
 			Err(Ok(err)) => match err.kind() {
-				error::ErrorKind::InvalidTransaction => Some(hashes[idx].clone()),
+				error::ErrorKind::InvalidTransaction(_) => Some(hashes[idx].clone()),
 				_ => None,
 			},
 			_ => None,
@@ -413,7 +413,7 @@ mod tests {
 			let nonce = uxt.transfer().nonce;
 
 			if nonce < block_number {
-				Ok(TransactionValidity::Invalid)
+				Ok(TransactionValidity::Invalid(0))
 			} else {
 				Ok(TransactionValidity::Valid {
 					priority: 4,