在使用 useMutation 时，需要手动添加 data 字段的返回值。具体的方法是在 useMutation 的返回值中使用 onCompleted 回调函数，将返回的结果设置到组件的状态中。示例代码如下：

import { useMutation } from '@apollo/client';
import { gql } from '@apollo/client/core';
import { useState } from 'react';

const CREATE_USER = gql`
  mutation CreateUser($input: UserInput!) {
    createUser(input: $input) {
      id
      username
    }
  }
`;

function NewUserForm() {
  const [username, setUsername] = useState('');
  const [createUserMutation, { loading }] = useMutation(CREATE_USER, {
    onCompleted: (data) => {
      setUserCreated(data.createUser);
    },
  });
  const [userCreated, setUserCreated] = useState(null);

  const createUser = () => {
    createUserMutation({ variables: { input: { username: username } } });
  };

  return (
    

       setUsername(e.target.value)} />
      Create User
      {loading && 
Creating user...
}
      {userCreated && 
User created with id: {userCreated.id}
}
    
  );
}

export default NewUserForm;