如何在 TypeScript 中为 React Apollo Query 组件编写 HOC？

Question

我正在尝试编写 HOC 以在组件中显示已用查询的信息，如下所示：

const GET_RATES = gql`
  query ratesQuery {
    rates(currency: "USD") {
      currency
      rate
    }
  }
`;

class RatesQuery extends Query<{
  rates: { currency: string; rate: string }[];
}> {}

const RatesQueryWithInfo = withQueryInfo(RatesQuery);

const Rates = () => (
  <RatesQueryWithInfo query={GET_RATES}>
    {({ loading, error, data }) => {
      if (loading) return "Loading...";
      if (error || !data) return "Error!";

      return (
        <div>
          {data.rates.map(rate => (
            <div key={rate.currency}>
              {rate.currency}: {rate.rate}
            </div>
          ))}
        </div>
      );
    }}
  </RatesQueryWithInfo>
);

withQueryInfo 看起来像（它的实现是基于article）：

const withVerbose = <P extends object>(
  WrappedComponent: React.ComponentType<P>
) =>
  class extends React.Component<P> {
    render() {
      return (
        <div>
          {(this.props as any).query.loc.source.body}
          <WrappedComponent {...this.props as P} />;
        </div>
      );
    }
  };

这个 HOC 工作正常（它在上面的原始组件中附加查询字符串）但是打字被破坏了

withQueryInfo(RatesQuery) 中的错误

Argument of type 'typeof RatesQuery' is not assignable to parameter of type 'ComponentType<QueryProps<{ rates: { currency: string; rate: string; }[]; }, OperationVariables>>'.
  Type 'typeof RatesQuery' is not assignable to type 'ComponentClass<QueryProps<{ rates: { currency: string; rate: string; }[]; }, OperationVariables>, any>'.
    Types of property 'propTypes' are incompatible.
      Type '{ client: Requireable<object>; children: Validator<(...args: any[]) => any>; fetchPolicy: Requireable<string>; notifyOnNetworkStatusChange: Requireable<boolean>; onCompleted: Requireable<(...args: any[]) => any>; ... 5 more ...; partialRefetch: Requireable<...>; }' is not assignable to type 'WeakValidationMap<QueryProps<{ rates: { currency: string; rate: string; }[]; }, OperationVariables>>'.
        Types of property 'fetchPolicy' are incompatible.
          Type 'Requireable<string>' is not assignable to type 'Validator<"cache-first" | "cache-and-network" | "network-only" | "cache-only" | "no-cache" | "standby" | null | undefined>'.
            Types of property '[nominalTypeHack]' are incompatible.
              Type 'string | null | undefined' is not assignable to type '"cache-first" | "cache-and-network" | "network-only" | "cache-only" | "no-cache" | "standby" | null | undefined'.
                Type 'string' is not assignable to type '"cache-first" | "cache-and-network" | "network-only" | "cache-only" | "no-cache" | "standby" | null | undefined'.ts(2345)

而且{ loading, error, data } 也隐含了一个“任意”类型。

此示例的 CodeSanbox 是 here。

如何为这个 HOC 编写合适的类型？

Answer 1

我的阅读方式是Query 组件中声明的propTypes 与QueryProps（该组件的道具）之间存在不匹配。错误的 props 修复如下（以 cmets 中的原始类型）：

export default class Query<TData = any, TVariables = OperationVariables> extends React.Component<QueryProps<TData, TVariables>> {
    static propTypes: {
        // ...
        client: PropTypes.Requireable<ApolloClient<any>>; //PropTypes.Requireable<object>;
        // ...
        fetchPolicy: PropTypes.Requireable<FetchPolicy>; //PropTypes.Requireable<string>;
        // ...
        query: PropTypes.Validator<DocumentNode>; // PropTypes.Validator<object>;
    };
}

这种不兼容性通常无关紧要，除非您尝试创建 HOC 并使用 React.ComponentType<P> 来验证 propTypes 和 props 是否一致。

最简单的解决方案（对 react-apollo 使用 PR）是为 WrappedComponent 使用较弱的类型，它不会验证 propTypes。

使用下面的定义，客户端代码可以按预期工作：

interface WeakComponentClass<P = {}, S = React.ComponentState> extends React.StaticLifecycle<P, S> {
  new (props: P, context?: any): React.Component<P, S>;
}

const withVerbose = <P extends any>(
  WrappedComponent: WeakComponentClass<P> | React.FunctionComponent<P>
) =>
  class extends React.Component<P> {
    render() {
      return (
        <div>
          {(this.props as any).query.loc.source.body}
          <WrappedComponent {...this.props as P} />;
        </div>
      );
    }
  };

注意：我犹豫是否提交带有更正类型的 PR，因为尽管它们修复了打字问题，但它们并不能准确反映 propTypes 所做的运行时验证。也许更好的方法是将 Validator<T> 在 react 中的行为改变为不是协变的，而是相反的。

使用Validator 的这个定义，react-apollo 按预期工作：

export interface Validator<T> {
    (props: object, propName: string, componentName: string, location: string, propFullName: string): Error | null;
    [nominalTypeHack]?: (p: T) => void; // originally T, now behaves contra-variantly 
}