hardhat/src/internal/builtin-plugins/clean/type-extensions.ts

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

declare module "../../../types/hooks.js" {
  export interface HardhatHooks {
    clean: CleanHooks;
  }

  export interface CleanHooks {
    onClean: (context: HookContext) => Promise<void>;
  }
}