Improvements and optimisations to estimate_gas (#4142)

* Return 0 instead of error with out of gas on estimate_gas

* Fix stuff up.

* Another estimate gas fix.

* Alter balance to maximum possible rather than GP=0.

* Only increase to amount strictly necessary.

* Improvements and optimisations to estimate_gas.

- Introduce proper error type
- Avoid building costly traces

* Fix tests.

* Actually fix testsActually fix tests

ethcore/src/client/client.rs

@@ -908,7 +908,7 @@ impl BlockChainClient for Client {
 
 			Executive::new(&mut state, &env_info, &*self.engine, &self.factories.vm)
 				.transact(&tx, options.clone())
-				.map(|r| r.trace[0].result.succeeded())
+				.map(|r| r.exception.is_some())
 				.unwrap_or(false)
 		};
 

ethcore/src/evm/evm.rs

@@ -22,7 +22,7 @@ use action_params::ActionParams;
 use evm::Ext;
 
 /// Evm errors.
-#[derive(Debug, Clone, Copy)]
+#[derive(Debug, Clone, Copy, PartialEq)]
 pub enum Error {
 	/// `OutOfGas` is returned when transaction execution runs out of gas.
 	/// The state should be reverted to the state from before the

ethcore/src/executive.rs

@@ -463,8 +463,9 @@ impl<'a> Executive<'a> {
 
 		match result {
 			Err(evm::Error::Internal) => Err(ExecutionError::Internal),
-			Err(_) => {
+			Err(exception) => {
 				Ok(Executed {
+					exception: Some(exception),
 					gas: t.gas,
 					gas_used: t.gas,
 					refunded: U256::zero(),
@@ -479,6 +480,7 @@ impl<'a> Executive<'a> {
 			},
 			_ => {
 				Ok(Executed {
+					exception: None,
 					gas: t.gas,
 					gas_used: gas_used,
 					refunded: refunded,

ethcore/src/types/executed.rs

@@ -18,6 +18,7 @@
 
 use util::{Bytes, U256, Address, U512};
 use rlp::*;
+use evm;
 use trace::{VMTrace, FlatTrace};
 use types::log_entry::LogEntry;
 use types::state_diff::StateDiff;
@@ -65,6 +66,9 @@ impl Decodable for CallType {
 #[derive(Debug, PartialEq, Clone)]
 #[cfg_attr(feature = "ipc", binary)]
 pub struct Executed {
+	/// True if the outer call/create resulted in an exceptional exit.
+	pub exception: Option<evm::Error>,
+
 	/// Gas paid up front for execution of transaction.
 	pub gas: U256,
 
@@ -178,6 +182,8 @@ pub enum CallError {
 	TransactionNotFound,
 	/// Couldn't find requested block's state in the chain.
 	StatePruned,
+	/// Couldn't find an amount of gas that didn't result in an exception.
+	Exceptional,
 	/// Error executing.
 	Execution(ExecutionError),
 }
@@ -195,6 +201,7 @@ impl fmt::Display for CallError {
 		let msg = match *self {
 			TransactionNotFound => "Transaction couldn't be found in the chain".into(),
 			StatePruned => "Couldn't find the transaction block's state in the chain".into(),
+			Exceptional => "An exception happened in the execution".into(),
 			Execution(ref e) => format!("{}", e),
 		};
 

rpc/src/v1/helpers/errors.rs

@@ -36,6 +36,7 @@ mod codes {
 	pub const UNKNOWN_ERROR: i64 = -32009;
 	pub const TRANSACTION_ERROR: i64 = -32010;
 	pub const EXECUTION_ERROR: i64 = -32015;
+	pub const EXCEPTION_ERROR: i64 = -32016;
 	pub const ACCOUNT_LOCKED: i64 = -32020;
 	pub const PASSWORD_INVALID: i64 = -32021;
 	pub const ACCOUNT_ERROR: i64 = -32023;
@@ -130,6 +131,14 @@ pub fn state_pruned() -> Error {
 	}
 }
 
+pub fn exceptional() -> Error {
+	Error {
+		code: ErrorCode::ServerError(codes::EXCEPTION_ERROR),
+		message: "The execution failed due to an exception.".into(),
+		data: None
+	}
+}
+
 pub fn no_work() -> Error {
 	Error {
 		code: ErrorCode::ServerError(codes::NO_WORK),
@@ -286,6 +295,7 @@ pub fn from_rlp_error(error: DecoderError) -> Error {
 pub fn from_call_error(error: CallError) -> Error {
 	match error {
 		CallError::StatePruned => state_pruned(),
+		CallError::Exceptional => exceptional(),
 		CallError::Execution(e) => execution(e),
 		CallError::TransactionNotFound => internal("{}, this should not be the case with eth_call, most likely a bug.", CallError::TransactionNotFound),
 	}

rpc/src/v1/tests/mocked/eth.rs

@@ -564,6 +564,7 @@ fn rpc_eth_code() {
 fn rpc_eth_call_latest() {
 	let tester = EthTester::default();
 	tester.client.set_execution_result(Ok(Executed {
+		exception: None,
 		gas: U256::zero(),
 		gas_used: U256::from(0xff30),
 		refunded: U256::from(0x5),
@@ -599,6 +600,7 @@ fn rpc_eth_call_latest() {
 fn rpc_eth_call() {
 	let tester = EthTester::default();
 	tester.client.set_execution_result(Ok(Executed {
+		exception: None,
 		gas: U256::zero(),
 		gas_used: U256::from(0xff30),
 		refunded: U256::from(0x5),
@@ -634,6 +636,7 @@ fn rpc_eth_call() {
 fn rpc_eth_call_default_block() {
 	let tester = EthTester::default();
 	tester.client.set_execution_result(Ok(Executed {
+		exception: None,
 		gas: U256::zero(),
 		gas_used: U256::from(0xff30),
 		refunded: U256::from(0x5),
@@ -668,6 +671,7 @@ fn rpc_eth_call_default_block() {
 fn rpc_eth_estimate_gas() {
 	let tester = EthTester::default();
 	tester.client.set_execution_result(Ok(Executed {
+		exception: None,
 		gas: U256::zero(),
 		gas_used: U256::from(0xff30),
 		refunded: U256::from(0x5),
@@ -703,6 +707,7 @@ fn rpc_eth_estimate_gas() {
 fn rpc_eth_estimate_gas_default_block() {
 	let tester = EthTester::default();
 	tester.client.set_execution_result(Ok(Executed {
+		exception: None,
 		gas: U256::zero(),
 		gas_used: U256::from(0xff30),
 		refunded: U256::from(0x5),

rpc/src/v1/tests/mocked/traces.rs

@@ -51,6 +51,7 @@ fn io() -> Tester {
 		block_hash: 10.into(),
 	}]);
 	*client.execution_result.write() = Some(Ok(Executed {
+		exception: None,
 		gas: 20_000.into(),
 		gas_used: 10_000.into(),
 		refunded: 0.into(),