bug(`anvil`): `eth_estimateGas` `max_fee_per_gas` overrides the `block.basefee` when simulating a transaction

[jakim929]

Component

Anvil

Have you ensured that all of these are up to date?

• Foundry
• Foundryup

What version of Foundry are you on?

forge 0.2.0 (e903484 2024-07-19T00:18:41.070490000Z)

What command(s) is the bug in?

anvil

Operating System

macOS (Apple Silicon)

Describe the bug

Opened an issue since I'm not sure if this is intended behavior.

when calling eth_estimateGas, the max_fee_per_gas parameter included in the tx ends up overwriting the block.basefee. Is there a reason for this? This makes it harder to estimate gas for contracts that rely on the value of block.basefee (although I see it's not a common issue).

the FeeDetails is created based on the transaction params, then

foundry/crates/anvil/src/eth/api.rs

Lines 2344 to 2350 in 5af9d16

	let fees = FeeDetails::new(
	request.gas_price,
	request.max_fee_per_gas,
	request.max_priority_fee_per_gas,
	request.max_fee_per_blob_gas,
	)?
	.or_zero_fees();

used in this line to override the block's basefee.

foundry/crates/anvil/src/eth/backend/mem/mod.rs

Lines 1155 to 1157 in 5af9d16

	if let Some(base) = max_fee_per_gas {
	env.block.basefee = U256::from(base);
	}

Given the spec here, I would expect that all that eth_estimateGas does is set the block gas limit if unspecified, not change anything about the block otherwise. Curious if this is intended behavior? Thanks in advance!

[mattsse]

I believe we can remove this

[jakim929]

thanks for the quick response! opened a PR here #8517