Add an escape hatch for ETH_RPC_URL not to be used as FORK_URL

[PaulRBerg]

The latest nightly release (2022-04-08) (9c2469) introduced a change in the way the ETH_RPC_URL environment variable is treated. It seems like when this is enabled, Foundry will now also use it as an alias for FORK_URL.

But it looks like there's no escape hatch. We can't keep ETH_RPC_URL as an environment variable without automatically having it used as a fork URL also. In certain cases, such as when my Internet connection is poor, I would prefer not to test my contracts on a remote RPC. But I would like to keep ETH_RPC_URL as a global environment variable on my machine, so I can use the cast CLI.

Thus here's my feature request: let us override this new default behavior. I think the simplest way would be to give FORK_URL the utmost priority: if that field is set, and it is set to the empty string, then ETH_PRC_URL should not be used as a fork URL anymore.

Example:

export ETH_RPC_URL="https://rinkeby.infura.io/v3/f0c8e45d48b34a8da606303a83df4d0b"
export FORK_URL=""

With these environment variables, Foundry should NOT use the RPC url for running the tests against a remote chain fork.

Alternatively, there could be a new configuration option in foundry.toml which provides an explicit escape hatch for this behavior.

[onbjerg]

I don't think FORK_URL is valid right now. I'm pinging @mds1, I think you've wanted ETH_RPC_URL to be valid for some time, and I know for sure others have.

Also pinging @mattsse @gakonst to see if they have some ideas/thoughts

[mattsse]

I've been bitten be something similar in the past, it's easy to forget that you set an env var previously and wonder why it takes so long suddenly.

so what we need to decide is

• should we pick up ETH_RPC_URL (aliases rn are FOUNDRY_ETH_RPC_URL and DAPP_ETH_RPC_URL) like we do now?

if yes

• how to opt out?

I think the easiest would indeed be an additional env flag that basically ignores forking?

[onbjerg]

Just removed this behavior, so this is not the case after the next nightly

[PaulRBerg]

Great!

[mds1]

I'm still not sure exactly what problem this was intended to solve. It sounds like the issue was people didn't want to type out long CLI commands, but in the case a better solution would be to configure foundry.toml properly and add better support for env vars in the config file as discussed #1034

(also @onbjerg from #1233 (comment) it sounds like you think I also originally wanted this feature, so sorry for being unclear there—I'm assuming you got that impression from #1034)

[gakonst]

Making Url -> Option<Url> solves this I think?

export ETH_RPC_URL=<..> # or FOUNDRY_FORK_URL
forge t # does not fork
forge t --rpc-url # forks with the env var, errors if the env var is none
forge t --rpc-url <..> # works with whatever arg was provided