hardhat/src/internal/builtin-plugins/network-manager/request-handlers/handlers/gas/automatic-gas-handler.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,
  JsonRpcRequest,
  JsonRpcResponse,
} from "../../../../../../types/providers.js";
import type { RequestHandler } from "../../types.js";

import { isObject } from "@nomicfoundation/hardhat-utils/lang";

import { getRequestParams } from "../../../json-rpc.js";

import { MultipliedGasEstimation } from "./multiplied-gas-estimation.js";

export const DEFAULT_GAS_MULTIPLIER = 1;

/**
 * This class modifies transaction requests by automatically estimating the gas required,
 * applying a multiplier to the estimated gas.
 *
 * It extends the `MultipliedGasEstimation` class
 * to handle the gas estimation logic. If no gas value is provided in the transaction,
 * the gas is automatically estimated before being added to the request.
 */
export class AutomaticGasHandler
  extends MultipliedGasEstimation
  implements RequestHandler
{
  readonly #methods: ReadonlySet<string> = new Set(["eth_sendTransaction"]);

  constructor(
    provider: EthereumProvider,
    gasMultiplier: number = DEFAULT_GAS_MULTIPLIER,
  ) {
    super(provider, gasMultiplier);
  }

  public isSupportedMethod(jsonRpcRequest: JsonRpcRequest): boolean {
    return this.#methods.has(jsonRpcRequest.method);
  }

  public async handle(
    jsonRpcRequest: JsonRpcRequest,
  ): Promise<JsonRpcRequest | JsonRpcResponse> {
    if (!this.isSupportedMethod(jsonRpcRequest)) {
      return jsonRpcRequest;
    }

    const params = getRequestParams(jsonRpcRequest);
    const [tx] = params;

    if (isObject(tx) && tx.gas === undefined) {
      tx.gas = await this.getMultipliedGasEstimation(params);
    }

    return jsonRpcRequest;
  }
}