Squid EVM typegen

Since @subsquid/evm-typegen@2.0.0

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:

as a plain JSON file(s):
```
npx squid-evm-typegen src/abi erc20.json
```
If you use this option, you can also place your JSON ABIs to the abi folder and run.
```
sqd typegen
```
Script is available in all EVM templates.
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
```

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 (see below)
`--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

Usage

Events

The EVM log data is provided by the event object with wrappers for each event defined in the ABI.

Example

Subscribe to two topics:

// generated by evm-typegen
import { events } from "./abi/weth";

const processor = new EvmBatchProcessor()
  .setDataSource({
    archive: 'https://eth.archive.subsquid.io',
  })
  .addLog([
    '0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2'
  ], {
    filter: [[
      events.Deposit.topic, events.Withdrawal.topic
    ]],
    data: {
      evmLog: {
          topics: true,
          data: true,
      },
    } as const,
  })

Decode event data:

processor.run(new TypeormDatabase(), async (ctx) => {
  for (let c of ctx.blocks) {
    for (let i of c.items) {
      if (i.kind === 'evmLog' && i.evmLog.topics[0] == events.Deposit.topic) {
        // type-safe decoding of the Deposit event data
        const amt = events.Deposit.decode(i.evmLog).wad
      }
    }
});

Transactions

Similar to events, transaction access is provided by the functions object for each contract method defined in the ABI.

Contract state calls

The typegen creates a wrapper Contract class for each contract. Create a Contract instance using the processor context and the block height at which the state should be queried.

Example

// generated by evm-typegen
import { Contract } from "./abi/weth";

let contractAddress = '0xC02aaA39b223FE8D0A0e5C4F27eAD9083C756Cc2'.toLowerCase()

processor.run(new TypeormDatabase(), async (ctx) => {
  for (let c of ctx.blocks) {
    // call totalSupply() at the current block
    let blockHeader = c.header
    let supply = await (new Contract(ctx, blockHeader, contractAddress).totalSupply())
  }
});

Batching contract state calls using the Multicall contract

Use the --multicall flag to generate the Multicall facade class for the MakerDAO Multicall contract. See Batch state queries for more context.

The Multicall facade exposes the method

tryAggregate<Args extends any[], R>(
    func: Func<Args, {}, R>,
    calls: [address: string, args: Args][],
    paging?: number
  ): Promise<MulticallResult<R>[]>

The arguments are as follows:

func: the contract function to be called
calls: an array of tuples [contractAddress: string, args]. Each specified contract will be called with the specified arguments.
paging an (optional) argument for the maximal number of calls to be batched into a single JSON PRC request. Note that large page sizes may cause timeouts.

A typical usage is as follows:

// generated by evm-typegen
import { functions } from "./abi/mycontract";
import { Multicall } from "./abi/multicall";

const MY_CONTRACT='0xac5c7493036de60e63eb81c5e9a440b42f47ebf5'

processor.run(new TypeormDatabase(), async (ctx) => {
  for (let c of ctx.blocks) {
    for (let i of c.items) {
        // some logic
    }
  }
  const lastBlock = ctx.blocks[ctx.blocks.length - 1];
  // Multicall address for Ethereum is 0x5ba1e12693dc8f9c48aad8770482f4739beed696
  const multicall = new Multicall(ctx, lastBlock, '0x5ba1e12693dc8f9c48aad8770482f4739beed696')
  // call MY_CONTRACT.myContractMethod("foo") and MY_CONTRACT.myContractMethod("bar")
  const args = ["foo", "bar"]
  const results = await multicall.tryAggregate(functions.myContractMethod, args.map(a => [MY_CONTRACT, a]) as [string, any[]], 100);

  results.forEach((res, i) => {
    if (res.success) {
      ctx.log.info(`Result for argument ${args[i]} is ${res.value}`);
    }
  }) 
});

Migration from `evm-typegen@1.x`

In evm-typegen@2.0, the --abi, and --output flags are replaced by the positional arguments. For example, the command
```
npx squid-evm-typegen --abi src/abi/ERC721.json --output src/abi/erc721.ts
```
is replaced with
```
npx squid-evm-typegen src/abi src/abi/ERC721.json
```
The events object generated by evm-typegen@2.0 exposes events by name, not by the full signature. For example,
```
events['UpdatedGravatar(uint256,address,string,string)'].decode(evmLog)
```
should be replaced with a more readable
```
events.UpdatedGravatar.decode(evmLog)
```

Squid EVM typegen

Usage​

Events​

Transactions​

Contract state calls​

Batching contract state calls using the Multicall contract​

Migration from evm-typegen@1.x​