Add decoded revert reason to response message (#224)

* Add decoded revert reason to response message

* Fix checker

client/rpc/src/lib.rs

@@ -46,10 +46,20 @@ pub fn error_on_execution_failure(reason: &ExitReason, data: &[u8]) -> Result<()
 				data: Some(Value::String("0x".to_string()))
 			})
 		},
-		ExitReason::Revert(e) => {
+		ExitReason::Revert(_) => {
+			let mut message = "VM Exception while processing transaction: revert".to_string();
+			// A minimum size of error function selector (4) + offset (32) + string length (32)
+			// should contain a utf-8 encoded revert reason.
+			if data.len() > 68 {
+				let message_len = data[36..68].iter().sum::<u8>();
+				let body: &[u8] = &data[68..68 + message_len as usize];
+				if let Ok(reason) = std::str::from_utf8(body) {
+					message = format!("{} {}", message, reason.to_string());
+				}
+			}
 			Err(Error {
 				code: ErrorCode::InternalError,
-				message: format!("evm revert: {:?}", e),
+				message,
 				data: Some(Value::String(data.to_hex()))
 			})
 		},

ts-tests/tests/test-revert-reason.ts

@@ -0,0 +1,65 @@
+import { expect } from "chai";
+import { step } from "mocha-steps";
+
+import { createAndFinalizeBlock, customRequest, describeWithFrontier } from "./util";
+import { AbiItem } from "web3-utils";
+
+describeWithFrontier("Frontier RPC (Revert Reason)", `simple-specs.json`, (context) => {
+
+	let contractAddress;
+
+	const GENESIS_ACCOUNT = "0x6be02d1d3665660d22ff9624b7be0551ee1ac91b";
+	const GENESIS_ACCOUNT_PRIVATE_KEY = "0x99B3C12287537E38C90A9219D4CB074A89A16E9CDB20BF85728EBD97C343E342";
+
+	// contract ExplicitRevertReason {
+	// 	function max10(uint256 a) public returns (uint256) {
+	// 		if (a > 10)
+	// 			revert("Value must not be greater than 10.");
+	// 		return a;
+	// 	}
+	// }
+	const REVERT_W_MESSAGE_BYTECODE = "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";
+
+	const TEST_CONTRACT_ABI = {
+		constant: true,
+		inputs: [{ internalType: "uint256", name: "a", type: "uint256" }],
+		name: "max10",
+		outputs: [{ internalType: "uint256", name: "b", type: "uint256" }],
+		payable: false,
+		stateMutability: "pure",
+		type: "function",
+	} as AbiItem;
+
+	before("create the contract", async function () {
+		this.timeout(15000);
+		const tx = await context.web3.eth.accounts.signTransaction(
+			{
+				from: GENESIS_ACCOUNT,
+				data: REVERT_W_MESSAGE_BYTECODE,
+				value: "0x00",
+				gasPrice: "0x01",
+				gas: "0x100000",
+			},
+			GENESIS_ACCOUNT_PRIVATE_KEY
+		);
+		const r = await customRequest(context.web3, "eth_sendRawTransaction", [tx.rawTransaction]);
+		await createAndFinalizeBlock(context.web3);
+		const receipt = await context.web3.eth.getTransactionReceipt(r.result);
+		contractAddress = receipt.contractAddress;
+	});
+
+	it("should fail with revert reason", async function () {
+		const contract = new context.web3.eth.Contract([TEST_CONTRACT_ABI], contractAddress, {
+			from: GENESIS_ACCOUNT,
+			gasPrice: "0x01",
+		});
+		try {
+			await contract.methods.max10(30).call();
+		} catch (error) {
+			expect(error.message).to.be.eq(
+				"Returned error: VM Exception while processing transaction: revert Value must not be greater than 10."
+			);
+		}
+	});
+
+});