anvil base fee increases to 1 after starting with 0 and sending many transactions

[alvrs]

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 (ce687fc 2023-06-15T00:05:25.914566000Z)

What command(s) is the bug in?

anvil -b 1 --block-base-fee-per-gas 0

Operating System

macOS (Apple Silicon)

Describe the bug

1. Start a new anvil node with anvil -b 1 --block-base-fee-per-gas 0.
2. Run cast block to confirm baseFeePerGas is 0
3. Execute a bunch of transactions (in my case deploying a MUD app, but shouldn't be specific to the type of transactions)
4. Run cast block again, baseFeePerGas is now 1

This is problematic for local environments where transactions are executed from accounts with no balance.

Note: this wasn't the case yet with this version:

[mattsse]

this could be a regression is a fix in #5067 actually

see

https://github.com/foundry-rs/foundry/pull/5067/files#diff-3363023cb8e5c61c1619e30709f220faf6b583bbe864719e91122b76df095048R143-R149

which increases the base fee, since it only moves up or down.

I think the right fix here would be to treat basefee of 0 as desired constant and never increase base fee of 0, because a basefee of 0 would technically be impossible