Export precompileAvailability from evm/precompiles/index.ts

[CedarMist]

This is a trivial fix to make the precompileAvailability list available, given than precompiles is also exported.

Why?

Unfortunately there are situations where it's necessary to monkey-patch custom precompiles into an application which uses ethereumjs and no other method is easily available.

While precompiles is exported the getPrecompile function will not let you use anything added to it as it does not pass the availability check. See:

ethereumjs-monorepo/packages/evm/src/precompiles/index.ts

Line 160 in b2df147

const availability = precompileAvailability[addr]

An alternative method is to override the getPrecompile function, with a fallback to the original getPrecompile method.

[jochem-brouwer]

That's true, but precompiles themselves are exported and you can add them as custom precompiles in the EVM.

But, nevertheless, it makes sense to export it.

[CedarMist]

and you can add them as custom precompiles in the EVM.

This is in the context where you don't have control over the EVM constructor without very intrusive patches to several third-party apps, or maintaining a fork of ethereumjs and patching the other apps to use it. I just need to add the precompiles to the global list before anything else creates an EVM instance, then they become available and it makes maintaining custom precompiles much easier.

[jochem-brouwer]

Yes, I agree. Since we are (likely) to change the name of this object (including the type), I have cherry-picked your commit in #2811

[jochem-brouwer]

Merged the PR :)

[CedarMist]

Awesome thanks!

[CedarMist]

@jochem-brouwer Just to follow up, here is an example use case where custom precompiles are added without patching a third-party product: xmzheng/hardhat-precompiles-plugin@c7d39ad