feat(forge): add fork_url as an alias for eth_rpc_url in foundry.toml

[OliverNChalk]

Component

Forge

Describe the feature you would like

Brief

A user is able to setup fork scenarios using the following declaration:

[arbitrum]
eth_rpc_url = "https://rpc.ankr.com/arbitrum"
match_contract = "Saddle"

If we want to continue the convention of letting config set CLI options, then it would make sense to alias fork_url to eth_rpc_url, as shown:

[arbitrum]
fork_url = "https://rpc.ankr.com/arbitrum"
match_contract = "Saddle"

This was prompted after testing the changes in: #1378

Scope

• Are eth_rpc_url in foundry.toml and forge test --fork-url already equivalent? Is priority given to the command line flag?
• Is it as simple as adding fork_url as an alias for eth_rpc_url, do we want to reverse the relationship and make eth_rpc_url an alias for fork_url?

Additional context

No response

[onbjerg]

Are eth_rpc_url in foundty.toml and forge test --fork-url already equivalent? Is priority given to the command line flag?

Yes, and yes.

Is it as simple as adding fork_url as an alias for eth_rpc_url, do we want to reverse the relationship and make eth_rpc_url an alias for fork_url?

I think it's easier to alias fork_url since Cast also depends on eth_rpc_url

[malawadd]

how would I approach this if i wanted to work on this issue

[onbjerg]

Actually, I think we might not want to create this alias since that would also run all tests in fork mode if ETH_RPC_URL is set globally. cc @mds1 for thoughts on this, I know this was not expected behavior when I implemented it the last time

[mds1]

I'm not sure I totally follow the suggesting aliasing and how it would affect config options/defaults, but:

• Allowing users to specify fork_url in the config as an alias for eth_rpc_url seems reasonable to me.
• Automatically forking if a FOUNDRY_FORK_URL env var is found also seems ok.
• The main thing we want to prevent is: the presence of an ETH_RPC_URL env var should not lead to tests forking from that URL. Having a globally defined ETH_RPC_URL is common for cast users, so we don't want that to affect tests.

Now that cast supports config files though, I wonder if this alias puts us in a weird spot: I might want tests to not fork, but cast to use e.g. Optimism by specifying an Optimism RPC in the config file's eth_rpc_url. AFAIK that is not currently doable because specifying eth_rpc_url will result in tests also forking?

So perhaps we want to decouple the two and have something like this?

• fork_url used to determine the network for forge
• eth_rpc_url to determine the network for cast, which defaults to fork_url if present, and ETH_RPC_URL env var if fork_url isn't present

[OliverNChalk]

To second @mds1's comments, the following scenario is currently not supported:

• Specify eth_rpc_url in config
• Pass in --fork-block-number on command line

In this scenario the following error will be returned:

[onbjerg]

Will close this as this is sort of supported now - you can add RPC URLs in the [rpc_endpoints] section of foundry.toml and alias one of them to ETH_RPC_URL, e.g.:

[rpc_endpoints]
mainnet = "${ETH_RPC_URL}"

I think that should cover this functionality, but please let me know if it didn't quite cover what you were asking for 🙂