Substrate EVM Support

We provide a custom data source processor for Parity's Frontier EVM and Acala's EVM+. This offers a simple way to filter and index both EVM and Substrate activity on many Polkadot networks within a single SubQuery project.

Tested and Supported networks

Theoretically all the following networks (and more) should also be supported since they implement Parity's Frontier EVM. Please let us know if you verify this and we can add them to the known support:

• Moonbeam
• Moonriver
• Moonbase Alpha
• Acala
• Karura
• Astar
• Shiden
• Automata
• Bitcountry
• Clover
• Darwinia
• Edgeware
• Gamepower
• Human
• InVarch
• T3rn
• PAID
• Manta
• Parastate
• Polkafoundry
• ChainX
• Gaia
• Thales
• Unique

You can also refer to the basic Moonriver EVM or Acala EVM+ example projects with an event and call handler. This project is also hosted live in the SubQuery Explorer here.

Getting started

1. Add the custom datasource as a dependency:

• Create a new project from an EVM template though subql init OR
• For existing projects, yarn add -D @subql/frontier-evm-processor or npm i @subql/acala-evm-processor --save-dev.

2. Add exports to your package.json like below in order for IPFS deployments to work

  ...
  "exports": {
    "frontierEvm": "./node_modules/@subql/frontier-evm-processor/dist/index.js"
    //"acalaEvm": "./node_modules/@subql/acala-evm-processor/dist/index.js",
    "chaintypes": "./src/chaintypes.ts" // chain types if required
  }

3. Import processor file to your project.ts like below

import { FrontierEvmDatasource } from "@subql/frontier-evm-processor";

const project: SubstrateProject<FrontierEvmDatasource> = {
  ...
  dataSources: [
    {
      // This is the datasource for Moonbeam's Native Substrate processor
      kind: "substrate/FrontierEvm",
      startBlock: 752073,
      processor: {
        file: "./node_modules/@subql/frontier-evm-processor/dist/bundle.js",
        options: {
          abi: "erc20",
          address: "0xe3e43888fa7803cdc7bea478ab327cf1a0dc11a7", // FLARE token https://moonscan.io/token/0xe3e43888fa7803cdc7bea478ab327cf1a0dc11a7
        },
      },
      assets: new Map([["erc20", { file: "./abis/erc20.abi.json" }]]),
      mapping: {...},
    },
  ],
}

3. Add a custom data source as described below.
4. Add handlers for the custom data source to your code.

Data Source Spec

Field	Type	Required	Description
kind	substrate/FrontierEvm of substrate/AcalaEVM	Yes	Type of the datasource
processor.file	"./node_modules/@subql/frontier-evm-processor/dist/bundle.js" or "./node_modules/@subql/acala-evm-processor/dist/bundle.js"	Yes	File reference to the data processor code
processor.options	ProcessorOptions	No	Options specific to the Frontier Processor
assets	{ [key: String]: { file: String }}	No	An object of external asset files

Processor Options

Field	Type	Required	Description
abi	String	No	The ABI that is used by the processor to parse arguments. MUST be a key of assets
address	String or null	No	A contract address where the event is from or call is made to. null will capture contract creation calls

Call Handlers

Works in the same way as substrate/CallHandler except with a different handler argument and minor filtering changes.

Field	Type	Required	Description
kind	substrate/FrontierEvmCall or substrate/AcalaEvmCall	Yes	Specifies that this is an Call type handler
filter	Call Filter	No	Filter the data source to execute

Call Filters

Field	Type	Example(s)	Description
function	String	0x095ea7b3, approve(address to,uint256 value)	Either Function Signature strings or the function sighash to filter the function called on the contract
from	String	0x6bd193ee6d2104f14f94e2ca6efefae561a4334b	An Ethereum address that sent the transaction

Handler Functions

Unlike a normal handler you will not get a SubstrateExtrinsic as the parameter, instead you will get a FrontierEvmCall or AcalaEvmCall which is based on Ethers TransactionResponse type.

Changes from the TransactionResponse type:

• It doesn't have wait and confirmations properties.
• A success property is added to know if the transaction was a success.
• args is added if the abi field is provided and the arguments can be successfully parsed. You can add a generic parameter like so to type args: FrontierEvmCall<{ from: string, to: string, value: BigNumber }>.

Event Handlers

Works in the same way as substrate/EventHandler except with a different handler argument and minor filtering changes.

Field	Type	Required	Description
kind	substrate/FrontierEvmEvent or substrate/AcalaEvmEvent	Yes	Specifies that this is an Event type handler
filter	Event Filter	No	Filter the data source to execute

Event Filters

Field	Type	Example(s)	Description
topics	String array	Transfer(address indexed from,address indexed to,uint256 value)	The topics filter follows the Ethereum JSON-PRC log filters, more documentation can be found here.

Note on topics:

There are a couple of improvements from basic log filters:

• Topics don't need to be 0 padded.
• Event Fragment strings can be provided and automatically converted to their id.

Codegen

If you're creating a new Substrate Frontier EVM or Acala EVM+ based project, the normal codegen command will also generate ABI types and save them into src/types using the npx typechain --target=ethers-v5 command, allowing you to bind these contracts to specific addresses in the mappings and call read-only contract methods against the block being processed. It will also generate a class for every contract event to provide easy access to event parameters, as well as the block and transaction the event originated from. All of these types are written to src/types/**.ts. In the example Moonriver EVM Starter SubQuery project, you would import these types like so.

import { GraphQLEntity1, GraphQLEntity2 } from "../types";

Handler Functions

Unlike a normal handler you will not get a SubstrateEvent as the parameter, instead you will get a FrontierEvmEvent or AcalaEvmEvent which is based on Ethers Log type.

Changes from the Log type:

• args is added if the abi field is provided and the arguments can be successfully parsed. You can add a generic parameter like so to type args: FrontierEvmEvent<{ from: string, to: string, value: BigNumber }>.

Frontier EVM

import { Approval, Transaction } from "../types";
import {
  FrontierEvmEvent,
  FrontierEvmCall,
} from "@subql/frontier-evm-processor";
import { BigNumber } from "ethers";

// Setup types from ABI
type TransferEventArgs = [string, string, BigNumber] & {
  from: string;
  to: string;
  value: BigNumber;
};
type ApproveCallArgs = [string, BigNumber] & {
  _spender: string;
  _value: BigNumber;
};

export async function handleFrontierEvmEvent(
  event: FrontierEvmEvent<TransferEventArgs>
): Promise<void> {
  const transaction = new Transaction(event.transactionHash);

  transaction.value = event.args.value.toBigInt();
  transaction.from = event.args.from;
  transaction.to = event.args.to;
  transaction.contractAddress = event.address;

  await transaction.save();
}

export async function handleFrontierEvmCall(
  event: FrontierEvmCall<ApproveCallArgs>
): Promise<void> {
  const approval = new Approval(event.hash);

  approval.owner = event.from;
  approval.value = event.args._value.toBigInt();
  approval.spender = event.args._spender;
  approval.contractAddress = event.to;

  await approval.save();
}

Acala EVM+

import { Approval, Transaction } from "../types";
import { AcalaEvmEvent, AcalaEvmCall } from "@subql/acala-evm-processor";
import { BigNumber } from "ethers";

// Setup types from ABI
type TransferEventArgs = [string, string, BigNumber] & {
  from: string;
  to: string;
  value: BigNumber;
};
type ApproveCallArgs = [string, BigNumber] & {
  _spender: string;
  _value: BigNumber;
};

export async function handleAcalaEvmEvent(
  event: AcalaEvmEvent<TransferEventArgs>
): Promise<void> {
  const transaction = new Transaction(event.transactionHash);

  transaction.value = event.args.value.toBigInt();
  transaction.from = event.args.from;
  transaction.to = event.args.to;
  transaction.contractAddress = event.address;

  await transaction.save();
}

export async function handleAcalaEvmCall(
  event: AcalaEvmCall<ApproveCallArgs>
): Promise<void> {
  const approval = new Approval(event.hash);

  approval.owner = event.from;
  approval.value = event.args._value.toBigInt();
  approval.spender = event.args._spender;
  approval.contractAddress = event.to;

  await approval.save();
}

Data Source Example

This is an extract from the project.ts manifest file.

Frontier EVM

{
  dataSources: [
    {
      // This is the datasource for Moonbeam's Native Substrate processor
      kind: "substrate/FrontierEvm",
      startBlock: 752073,
      processor: {
        file: "./node_modules/@subql/frontier-evm-processor/dist/bundle.js",
        options: {
          abi: "erc20",
          address: "0xe3e43888fa7803cdc7bea478ab327cf1a0dc11a7", // FLARE token https://moonscan.io/token/0xe3e43888fa7803cdc7bea478ab327cf1a0dc11a7
        },
      },
      assets: new Map([["erc20", { file: "./erc20.abi.json" }]]),
      mapping: {
        file: "./dist/index.js",
        handlers: [
          {
            handler: "handleEvmEvent",
            kind: "substrate/FrontierEvmEvent",
            filter: {
              topics: [
                "Transfer(address indexed from,address indexed to,uint256 value)",
              ],
            },
          },
          {
            handler: "handleEvmCall",
            kind: "substrate/FrontierEvmCall",
            filter: {
              function: "approve(address to,uint256 value)",
            },
          },
        ],
      },
    },
  ],
}

Acala EVM+

{
  dataSources: [
    {
      // This is the datasource for Acala's EVM processor
      kind: "substrate/AcalaEvm",
      startBlock: 1000000,
      processor: {
        file: "./node_modules/@subql/acala-evm-processor/dist/bundle.js",
        options: {
          abi: "erc20",
          address: "0x0000000000000000000100000000000000000000", // ACA Token https://blockscout.acala.network/address/0x0000000000000000000100000000000000000000
        },
      },
      assets: new Map([["erc20", { file: "./erc20.abi.json" }]]),
      mapping: {
        file: "./dist/index.js",
        handlers: [
          {
            handler: "handleAcalaEvmEvent",
            kind: "substrate/AcalaEvmEvent",
            filter: {
              topics: [
                "Transfer(address indexed from,address indexed to,uint256 value)",
              ],
            },
          },
          {
            handler: "handleAcalaEvmCall",
            kind: "substrate/AcalaEvmCall",
            filter: {
              function: "approve(address to,uint256 value)",
            },
          },
        ],
      },
    },
  ],
}

Querying contracts

@subql/frontier-evm-processor is the only package that currently allows this. It provides FrontierEthProvider which implements an Ethers Provider, this implementation is restricted to only support methods for the current height. You can pass it to a contract instance in order to query contract state at the hight currently being indexed.

Known Limitations

• There is no way to get the transaction receipts with call handlers.
• blockHash properties are currently left undefined, the blockNumber property can be used instead.

Extra info

• There is also a @subql/moonbeam-evm-processor which is an alias for @subql/frontier-evm-processor.
• The source code for these processors can be found in our datasource-processors repo.