Add gas_limit_multiplier_support runtime api (#935)

* Add `gas_limit_multiplier_support` runtime api

* fmt

* clippy

* Ts test default gas limit

* prettier

client/rpc/src/eth/execute.rs

@@ -151,7 +151,12 @@ where
 				}
 				amount
 			}
-			None => max_gas_limit,
+			// If gas limit is not specified in the request we either use the multiplier if supported
+			// or fallback to the block gas limit.
+			None => match api.gas_limit_multiplier_support(&id) {
+				Ok(_) => max_gas_limit,
+				_ => block_gas_limit,
+			},
 		};
 
 		let data = data.map(|d| d.0).unwrap_or_default();
@@ -367,6 +372,8 @@ where
 
 		let max_gas_limit = block_gas_limit * self.execute_gas_limit_multiplier;
 
+		let api = client.runtime_api();
+
 		// Determine the highest possible gas limits
 		let mut highest = match request.gas {
 			Some(amount) => {
@@ -378,11 +385,14 @@ where
 				}
 				amount
 			}
-			None => max_gas_limit,
+			// If gas limit is not specified in the request we either use the multiplier if supported
+			// or fallback to the block gas limit.
+			None => match api.gas_limit_multiplier_support(&BlockId::Hash(best_hash)) {
+				Ok(_) => max_gas_limit,
+				_ => block_gas_limit,
+			},
 		};
 
-		let api = client.runtime_api();
-
 		// Recap the highest gas allowance with account's balance.
 		if let Some(from) = request.from {
 			let gas_price = gas_price.unwrap_or_default();

primitives/rpc/src/lib.rs

@@ -164,6 +164,9 @@ sp_api::decl_runtime_apis! {
 		) -> Vec<ethereum::TransactionV2>;
 		/// Return the elasticity multiplier.
 		fn elasticity() -> Option<Permill>;
+		/// Used to determine if gas limit multiplier for non-transactional calls (eth_call/estimateGas)
+		/// is supported.
+		fn gas_limit_multiplier_support();
 	}
 
 	#[api_version(2)]

template/runtime/src/lib.rs

@@ -744,6 +744,8 @@ impl_runtime_apis! {
 		fn elasticity() -> Option<Permill> {
 			Some(BaseFee::elasticity())
 		}
+
+		fn gas_limit_multiplier_support() {}
 	}
 
 	impl fp_rpc::ConvertTransactionRuntimeApi<Block> for Runtime {

ts-tests/contracts/ForceGasLimit.sol

@@ -0,0 +1,12 @@
+// SPDX-License-Identifier: MIT
+
+pragma solidity ^0.8.0;
+
+contract ForceGasLimit  {
+    uint public number;
+    function force_gas(uint require_gas) public returns (uint) {
+        require(gasleft() > require_gas, "not enough gas");
+        number++;
+        return number;
+    }
+}

ts-tests/tests/test-execute.ts

@@ -1,16 +1,22 @@
 import { assert, expect } from "chai";
 import { step } from "mocha-steps";
-import { BLOCK_GAS_LIMIT, GENESIS_ACCOUNT } from "./config";
+import { BLOCK_GAS_LIMIT, GENESIS_ACCOUNT, GENESIS_ACCOUNT_PRIVATE_KEY } from "./config";
 
-import { describeWithFrontier, customRequest } from "./util";
+import { describeWithFrontier, customRequest, createAndFinalizeBlock } from "./util";
+import { AbiItem } from "web3-utils";
 
 import Test from "../build/contracts/Test.json";
+import ForceGasLimit from "../build/contracts/ForceGasLimit.json";
 
 // EXTRINSIC_GAS_LIMIT = [BLOCK_GAS_LIMIT - BLOCK_GAS_LIMIT * (NORMAL_DISPATCH_RATIO - AVERAGE_ON_INITIALIZE_RATIO) - EXTRINSIC_BASE_Weight] / WEIGHT_PER_GAS = (1_000_000_000_000 * 2 * (0.75-0.1) - 125_000_000) / 20000
 const EXTRINSIC_GAS_LIMIT = 64995685;
 const TEST_CONTRACT_BYTECODE = Test.bytecode;
 const TEST_CONTRACT_DEPLOYED_BYTECODE = Test.deployedBytecode;
 
+const FORCE_GAS_CONTRACT_BYTECODE = ForceGasLimit.bytecode;
+const FORCE_GAS_CONTRACT_ABI = ForceGasLimit.abi as AbiItem[];
+const FORCE_GAS_CONTRACT_DEPLOYED_BYTECODE = ForceGasLimit.deployedBytecode;
+
 describeWithFrontier("Frontier RPC (RPC execution)", (context) => {
 	step("should call with gas limit under block gas limit", async function () {
 		const result = await customRequest(context.web3, "eth_call", [
@@ -88,4 +94,43 @@ describeWithFrontier("Frontier RPC (RPC execution)", (context) => {
 			"provided gas limit is too high (can be up to 10x the block gas limit)"
 		);
 	});
+
+	step("should use the gas limit multiplier fallback", async function () {
+		const contract = new context.web3.eth.Contract(FORCE_GAS_CONTRACT_ABI);
+
+		const tx = await context.web3.eth.accounts.signTransaction(
+			{
+				from: GENESIS_ACCOUNT,
+				data: FORCE_GAS_CONTRACT_BYTECODE,
+				value: "0x00",
+				gasPrice: "0x3B9ACA00",
+				gas: "0x100000",
+			},
+			GENESIS_ACCOUNT_PRIVATE_KEY
+		);
+
+		await customRequest(context.web3, "eth_sendRawTransaction", [tx.rawTransaction]);
+		await createAndFinalizeBlock(context.web3);
+
+		const block = await context.web3.eth.getBlock("latest");
+
+		let receipt = await context.web3.eth.getTransactionReceipt(tx.transactionHash);
+		let contractAddress = receipt.contractAddress;
+
+		// When not specifying gas we expect the gas limit to default to a 10x block gas limit
+		// non-transactional call. The contract's method used requires close to block gas limit * 10.
+		const result = await customRequest(context.web3, "eth_call", [
+			{
+				to: contractAddress,
+				// require something close to the block gas limit * 10
+				data: contract.methods.force_gas(block.gasLimit * 10 - 500_000).encodeABI(),
+			},
+		]);
+
+		expect(result).to.include({
+			jsonrpc: "2.0",
+			result: "0x0000000000000000000000000000000000000000000000000000000000000001",
+			id: 1,
+		});
+	});
 });