feat(anvil): add --fund-accounts CLI flag

[exp0nge]

Motivation

When testing with Anvil, it's common to need specific addresses funded with custom balances on startup (e.g. for impersonation testing or reproducing on-chain scenarios). Currently this requires sending transactions after startup or using a custom genesis file.

Solution

Add a --fund-accounts CLI flag that accepts ADDRESS:AMOUNT pairs (amount in ETH):

anvil --fund-accounts 0x1234...5678:1000 0xabcd...ef01:5000

This funds the specified addresses during node initialization, after state loading but before the node is ready.

• Add --fund-accounts arg to NodeArgs with space-delimited values
• Add funded_accounts field + with_funded_accounts() builder to NodeConfig
• Apply funding via set_balance during backend setup

PR Checklist

• Added Tests
• Added Documentation
• Breaking changes

[mablr]

Hi, thanks for you proposition.

Just wondering why anvil_setBalance/anvil_addBalance endpoints aren't enough ?

[exp0nge]

Hi, thanks for you proposition.

Just wondering why anvil_setBalance/anvil_addBalance endpoints aren't enough ?

This would be a one-shot (startup) option. IIUC the anvil_* namespace would need to be part of the post startup bootstrapping?

[mablr]

IIUC the anvil_* namespace would need to be part of the post startup

Yes simply call anvil_setBalance/anvil_addBalance endpoints after startup.

Is there a specific use-case where this is not suitable ? If so could please you elaborate more ?

[exp0nge]

IIUC the anvil_* namespace would need to be part of the post startup

Yes simply call anvil_setBalance/anvil_addBalance endpoints after startup.

Is there a specific use-case where this is not suitable ? If so could please you elaborate more ?

We are using this as a drop-in replacement for other dev/localnets which come with some pre-funded addresses. Similar to the genesis configurations where you can bake in your addresses. Post-boostrap would be extra setup, I can do that and close this PR if you don't think this is worth as a extra feature

[mablr]

I see, it shouldn't hurt to have this.

Could you please resolve the merge conflict? Once done, I’ll trigger CI. 👍

[exp0nge]

I see, it shouldn't hurt to have this.

Could you please resolve the merge conflict? Once done, I’ll trigger CI. 👍

done