@dzlzv/hydra-typegen v3.0.0

Hydra Typegen

Motivation

Hydra Typegen is a code generation tool for creating Typescript types for substrate events and extrinsics. Its primary use-case is to provide type-safe interfaces for Hydra mappings. For example, once a typescript class for the Balances.Transfer event is generated, a mapping can look like

export async function balancesTransfer(
  db: DatabaseManager,
  _event: SubstrateEvent
) {
  const event = new Balances.TransferEvent(_event);
  const transfer = new Transfer()
  transfer.from = Buffer.from(event.data.accountIds[0].toHex())
  transfer.to = Buffer.from(event.data.accountIds[1].toHex())
  transfer.value = event.data.balance.toBn()
  transfer.block = event.ctx.blockNumber
  transfer.comment = `Transferred ${transfer.value} from ${transfer.from} to ${transfer.to}`

  console.log(`Saving ${JSON.stringify(transfer, null, 2)}`)

  await db.save<Transfer>(transfer)
}

A full sample Hydra project can be found here

Usage

For usage and a list of supported flags, type

hydra-typegen typegen --help

A minimal example for generating classes for the Balances.Transfer and Treasury.Deposit events in Kusama:

hydra-typegen typegen --metadata wss://kusama-rpc.polkadot.io Balances.Transfer,Treasury.Deposit

It is also possible to run hydra-typegen against a manifest file:

hydra-typegen typegen typegen.yml --debug

The config file typegen.yml can look like this:

# Typegen will pull the metadata from Kusama at block with the given hash
metadata:
  source: wss://kusama-rpc.polkadot.io
  blockHash: '0x45eb7ddd324361adadd4f8cfafadbfb7e0a26393a70a70e5bee6204fc46af62e'
# events and calls for which the typescript types will be generated
events:
  - Balances.Transfer
calls:
  - Balances.transfer
outDir: ./generated

Hydra-typegen also supports config files like the one below:

metadata:
  source: wss://kusama-rpc.polkadot.io
  blockHash: '0x45eb7ddd324361adadd4f8cfafadbfb7e0a26393a70a70e5bee6204fc46af62e'
events:
  - Balances.Transfer
calls:
  - Balances.transfer
outDir: ./generated

Simply run hydra-typegen <path-to-config-file>

Custom types

Hydra Typegen supports custom substrate types via the --typedefs flag. The provided .json file should include type definitions for the arguments and parameters of the events and extrinsics to be generated. The type definitions file is copied to the generated sources.

In the config file, place the definition into the customTypes section. It assumes that all the custom runtime types are already available for import from a library, so that e.g. the generated import statement

import { MyCustomRuntimeClass } from 'my/types/definitions

is correctly resolved.

...
customTypes: 
    lib: <from where the custom types are imported>,
    typedefs: <path to a json file with custom runtime types definitions>,