Generating utility modules

squid-evm-typegen

The squid-evm-typegen(1) tool generates TypeScript facades for EVM transactions, logs and eth_call queries.

The generated facades are assumed to be used by squids indexing EVM data.

The tool takes a JSON ABIs as an input. Those can be specified in three ways:

1. as a plain JSON file(s):

   npx squid-evm-typegen src/abi abi/erc20.json

   To include all files in ./abi and add an interface for the Multicall contract, run

   npx squid-evm-typegen ./src/abi ./abi/*.json --multicall

2. as a contract address (to fetch the ABI from Etherscan API). Once can pass multiple addresses at once.

   npx squid-evm-typegen src/abi 0xBB9bc244D798123fDe783fCc1C72d3Bb8C189413

info

Please check if your contract is a proxy when using this method. If it is, consult this page for guidance.

3. as an arbitrary URL:

   npx squid-evm-typegen src/abi https://example.com/erc721.json

In all cases typegen will use basename of the ABI as the root name for the generated files. You can change the basename of generated files using the fragment (#) suffix.

squid-evm-typegen src/abi 0xBB9bc244D798123fDe783fCc1C72d3Bb8C189413#my-contract-name

Arguments:

output-dir	output directory for generated definitions
abi	A contract address, an URL or a local path to the ABI file. Accepts multiple contracts.

Options:

--multicall	generate a facade for the MakerDAO multicall contract. May significantly improve the performance of contract state calls by batching RPC requests
--etherscan-api <url>	etherscan API to fetch contract ABI by a known address. By default, https://api.etherscan.io/
--clean	delete output directory before the run
-h, --help	display help for command

warning

The generated modules depend on @subsquid/evm-abi. Please add it to your package.json as a peer dependency if it's not there already:

npm i @subsquid/evm-abi

Usage

The generated utility modules have three intended uses:

1. Constants: EVM log topic0 values and sighashes for transactions. Example:

   // generated by evm-typegen
   import * as weth from './abi/weth'
   
   const CONTRACT_ADDRESS = '0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2'.toLowerCase()
   
   const processor = new EvmBatchProcessor()
     .setGateway('https://v2.archive.subsquid.io/network/ethereum-mainnet')
     .addLog({
       address: [CONTRACT_ADDRESS],
       topic0: [
         weth.events.Deposit.topic,
         weth.events.Withdrawal.topic
       ]
     })

2. Decoding of EVM logs and transactions

3. Direct chain state queries, including queries to multicall.

squid-substrate-typegen

The substrate typegen tool is a part of Squid SDK. It generates TypeScript wrappers for interfacing Substrate events and calls.

Usage:

npx squid-substrate-typegen typegen.json

If necessary, multiple config files can be supplied:

npx squid-substrate-typegen typegen0.json typegen1.json ...

The structure of the typegen.json config file is best illustrated with an example:

{
  "outDir": "src/types",
  "specVersions": "https://v2.archive.subsquid.io/metadata/kusama",
  "pallets": {
    // add one such section for each pallet
    "Balances": {
      "events": [
        // list of events to generate wrappers for
        "Transfer"
      ],
      "calls": [
        // list of calls to generate wrappers for
        "transfer_allow_death"
      ],
      "storage": [
        "Account"
      ],
      "constants": [
        "ExistentialDeposit"
      ]
    }
  }
}

The specVersions field is either

• a metadata service endpoint URL, like

  https://v2.archive.subsquid.io/metadata/{network}
  or
• a path to a jsonl file generated by substrate-metadata-explorer(1).

To generate all items defined by a given pallet, set any of the events, calls, storage or constants fields to true, e.g.

{
  "outDir": "src/types",
  "specVersions": "kusamaVersions.jsonl",
  "pallets": {
    "Balances": {
      // generate wrappers for all Balances pallet constants
      "constants": true
    }
  }
}

info

In the rare cases when the typegen needs a types bundle, supply it alongside metadata:

{
  "outDir": "src/types",
  "specVersions": "westendVersions.jsonl",
  "typesBundle": "westendTypes.json",
  ...
}

TypeScript wrappers

Wrappers generated by the typegen command can be found in the specified outDir (src/types by convention). Assuming that this folder is imported as types (e.g. with import * as types from './types'), you'll be able to find the wrappers at:

• for events: types.events.${palletName}.${eventName}
• for calls: types.calls.${palletName}.${callName}
• for storage items: types.storage.${palletName}.${storageItemName}
• for constants: types.constants.${palletName}.${constantName}

All identifiers (pallet name, call name etc) are lowerCamelCased. E.g. the constant Balances.ExistentialDeposit becomes types.events.balances.existentialDeposit and the call Balances.set_balance becomes types.calls.setBalance.

Usage

1. Item name constants (e.g. events.balances.transfer.name).

2. Runtime versioning-aware decoding.

3. Chain storage queries

4. Runtime constants:

   import {constants} from './types'
   // ...
   processor.run(new TypeormDatabase(), async ctx => {
     for (let block of ctx.blocks) {
       if (constants.balances.existentialDeposit.v1020.is(block.header)) {
         let c = new constants.balances.existentialDeposit.v1020.get(block.header)
         ctx.log.info(`Balances.ExistentialDeposit (runtime version V1020): ${c}`)
       }
     }
   })

squid-ink-typegen

Use squid-ink-typegen to generate facade classes for decoding ink! smart contract data from JSON ABI metadata.

Usage:

npx squid-ink-typegen --abi abi/erc20.json --output src/abi/erc20.ts

The generated source code exposes the decoding methods, some useful types and a class for performing wrapped RPC queries, using @subsquid/ink-abi under the hood