Macro init

macro_rules! init {
    () => { ... };
}

The init macro registers a custom get random function in the system which is required because ethabi that we rely on for ABI decoding/encoding primitives use it somewhere in its transitive set of dependencies and causes problem in wasm32-unknown-unknown target.

This macro must be invoked in the root crate so you must have the substreams_ethereum::init!() call in your lib.rs of your Substreams.

In addition, you need to have getrandom = { version = "0.2", features = ["custom"] } dependency in your Substreams Cargo.toml file:

# Required so that ethabi > ethereum-types build correctly under wasm32-unknown-unknown
[target.wasm32-unknown-unknown.dependencies]
getrandom = { version = "0.2", features = ["custom"] }