Better error message for rpc gas price errors

ethcore/types/src/transaction/error.rs

@@ -42,6 +42,14 @@ pub enum Error {
 		/// Transaction gas price
 		got: U256,
 	},
+	/// Transaction has too low fee
+	/// (there is already a transaction with the same sender-nonce but higher gas price)
+	TxTooCheapToReplace {
+		/// previous transaction's gas price
+		prev: U256,
+		/// new transaction's gas price
+		new: U256,
+	},
 	/// Transaction's gas is below currently set minimal gas requirement.
 	InsufficientGas {
 		/// Minimal expected gas
@@ -102,6 +110,10 @@ impl fmt::Display for Error {
 			AlreadyImported => "Already imported".into(),
 			Old => "No longer valid".into(),
 			TooCheapToReplace => "Gas price too low to replace".into(),
+			TxTooCheapToReplace { prev, new } =>
+				format!("Gas price too low to replace, previous tx gas: {}, new tx gas: {}",
+						prev, new
+				),
 			LimitReached => "Transaction limit reached".into(),
 			InsufficientGasPrice { minimal, got } =>
 				format!("Insufficient gas price. Min={}, Given={}", minimal, got),

miner/src/pool/tests/mod.rs

@@ -93,7 +93,7 @@ fn should_return_correct_nonces_when_dropped_because_of_limit() {
 	assert_eq!(res2, vec![
 			   // The error here indicates reaching the limit
 			   // and minimal effective gas price taken into account.
-			   Err(transaction::Error::InsufficientGasPrice { minimal: 2.into(), got: 1.into() }),
+			   Err(transaction::Error::TxTooCheapToReplace { prev: 2.into(), new: 1.into() }),
 			   Ok(())
 	]);
 	assert_eq!(txq.status().status.transaction_count, 3);
@@ -1027,9 +1027,9 @@ fn should_reject_early_in_case_gas_price_is_less_than_min_effective() {
 	let client = TestClient::new();
 	let tx1 = Tx::default().signed().unverified();
 	let res = txq.import(client.clone(), vec![tx1]);
-	assert_eq!(res, vec![Err(transaction::Error::InsufficientGasPrice {
-		minimal: 2.into(),
-		got: 1.into(),
+	assert_eq!(res, vec![Err(transaction::Error::TxTooCheapToReplace {
+		prev: 2.into(),
+		new: 1.into(),
 	})]);
 	assert!(!client.was_verification_triggered());
 

miner/src/pool/verifier.rs

@@ -231,9 +231,9 @@ impl<C: Client> txpool::Verifier<Transaction> for Verifier<C, ::pool::scoring::N
 						tx.gas_price(),
 						vtx.transaction.gas_price,
 					);
-					return Err(transaction::Error::InsufficientGasPrice {
-						minimal: vtx.transaction.gas_price,
-						got: *tx.gas_price(),
+					return Err(transaction::Error::TxTooCheapToReplace {
+						prev: vtx.transaction.gas_price,
+						new: *tx.gas_price(),
 					});
 				}
 			}

rpc/src/v1/helpers/errors.rs

@@ -423,6 +423,9 @@ pub fn transaction_message(error: &TransactionError) -> String {
 		TooCheapToReplace => {
 			"Transaction gas price is too low. There is another transaction with same nonce in the queue. Try increasing the gas price or incrementing the nonce.".into()
 		}
+		TxTooCheapToReplace { prev, new } => {
+			format!("Transaction gas price {}wei is too low. There is another transaction with same nonce in the queue with gas price: {}wei. Try increasing the gas price or incrementing the nonce.", new, prev)
+		}
 		LimitReached => {
 			"There are too many transactions in the queue. Your transaction was dropped due to limit. Try increasing the fee.".into()
 		}