provider.getFeeData().maxPriorityFeePerGas vs eth_maxPriorityFeePerGas different values

[JeremyX2022]

Version of Hardhat

2.20

What happened?

Why the value of maxPriorityFeePerGas are different by using these two methods?
I tested it on the Ethereum mainnet

Minimal reproduction steps

1. config hardhat network:

  networks: {
    mainnet: {
      url: "https://eth.llamarpc.com",
    },
  }

2. goto hardhat console: npx hardhat console --network mainnet

3. using following codes:

const p = new ethers.JsonRpcProvider("https://eth.llamarpc.com")

console.log([(await ethers.provider.getFeeData()), Number(await ethers.provider.send('eth_maxPriorityFeePerGas', []))]);
console.log([(await p.getFeeData()), Number(await p.send('eth_maxPriorityFeePerGas', []))]);

output:

> [
  FeeData {
    gasPrice: 16951633560n,
    maxFeePerGas: 34883267120n,
    maxPriorityFeePerGas: 1000000000n
  },
  10000000
]


> [
  FeeData {
    gasPrice: 16951633560n,
    maxFeePerGas: 33893267120n,
    maxPriorityFeePerGas: 10000000n
  },
  10000000
]

You can see 'maxPriorityFeePerGas' in 'getFeeData' is different from the value of 'eth_maxPriorityFeePerGas' by using ethers.provider.

Search terms

No response

[kanej]

Hey @JeremyX2022, can I confirm the version of ethers you are using here?

[JeremyX2022]

Hey @JeremyX2022, can I confirm the version of ethers you are using here?

ethers.version
'6.11.1'

[JeremyX2022]

I also post in ethers: ethers-io/ethers.js#4656
but the issue seems more related to hardhat

[kanej]

I can reproduce this locally. It appears that ethers delegates to eth_maxPriorityFeePerGas RPC call for calculating gas falling back to a default of 1_000_000_000n and the Harhdat hardhat-ethers-provider always returns the default:

hardhat/packages/hardhat-ethers/src/internal/hardhat-ethers-provider.ts

Lines 144 to 158 in dc6840c

	public async getFeeData(): Promise<ethers.FeeData> {
	let gasPrice: bigint | undefined;
	let maxFeePerGas: bigint | undefined;
	let maxPriorityFeePerGas: bigint | undefined;
	try {
	gasPrice = BigInt(await this._hardhatProvider.send("eth_gasPrice"));
	} catch {}
	const latestBlock = await this.getBlock("latest");
	const baseFeePerGas = latestBlock?.baseFeePerGas;
	if (baseFeePerGas !== undefined && baseFeePerGas !== null) {
	maxPriorityFeePerGas = 1_000_000_000n;
	maxFeePerGas = 2n * baseFeePerGas + maxPriorityFeePerGas;
	}

We should update this logic to match the ethers logic.

[sambacha]

it should be noted that eth_maxPriorityFeePerGas was not originally part of the official Ethereum JSON-RPC specification and originally a go-ethereum only RPC method. It is now part of the execution api spec.