hardhat/src/internal/builtin-plugins/network-manager/request-handlers/handlers/chain-id/chain-id.ts

Hardhat is an extensible developer tool that helps smart contract developers increase productivity by reliably bringing together the tools they want.

import type { EthereumProvider } from "../../../../../../types/providers.js";

import { assertHardhatInvariant } from "@nomicfoundation/hardhat-errors";
import {
  hexStringToNumber,
  isPrefixedHexString,
} from "@nomicfoundation/hardhat-utils/hex";

/**
 * This class is responsible for retrieving the chain ID of the network.
 * It uses the provider to fetch the chain ID via two methods: 'eth_chainId' and,
 * as a fallback, 'net_version' if the first one fails. The chain ID is cached
 * after being retrieved to avoid redundant requests.
 */
export class ChainId {
  protected readonly provider: EthereumProvider;

  #chainId: number | undefined;

  constructor(provider: EthereumProvider) {
    this.provider = provider;
  }

  protected async getChainId(): Promise<number> {
    if (this.#chainId === undefined) {
      try {
        this.#chainId = await this.#getChainIdFromEthChainId();
      } catch {
        // If eth_chainId fails we default to net_version
        this.#chainId = await this.#getChainIdFromEthNetVersion();
      }
    }

    return this.#chainId;
  }

  async #getChainIdFromEthChainId(): Promise<number> {
    const id = await this.provider.request({
      method: "eth_chainId",
    });

    assertHardhatInvariant(typeof id === "string", "id should be a string");

    return hexStringToNumber(id);
  }

  async #getChainIdFromEthNetVersion(): Promise<number> {
    const id = await this.provider.request({
      method: "net_version",
    });

    assertHardhatInvariant(typeof id === "string", "id should be a string");

    // There's a node returning this as decimal instead of QUANTITY.
    // TODO: from V2 - Document here which node does that
    return isPrefixedHexString(id) ? hexStringToNumber(id) : parseInt(id, 10);
  }
}