What causes "dcpCode and clsNo cannot be used at the same time" in DIYgod/RSSHub?

Supply at most one of dcpCode or clsNo in the path's query string.

DIYgod/RSSHub · error · Error

dcpCode and clsNo cannot be used at the same time

Error message

dcpCode and clsNo cannot be used at the same time

What it means

The BUAA library new-book route parses the tail of the path as URLSearchParams and supports filtering by subject (dcpCode) OR by Chinese Library Classification (clsNo), but not both. The downstream API selects either a `/bysubject` or `/byclass` endpoint based on which filter is present, so supplying both is ambiguous and the handler throws a generic Error before building the URL.

Source

Thrown at lib/routes/buaa/lib/space/newbook.tsx:125

        requireConfig: false,
        requirePuppeteer: false,
        antiCrawler: false,
        supportRadar: false,
        supportBT: false,
        supportPodcast: false,
        supportScihub: false,
    },
};

async function handler(ctx: Context): Promise<Data> {
    const path = ctx.req.param('path');
    const i = path!.indexOf('/');
    const params = i === -1 ? '' : path!.slice(i + 1);
    const searchParams = new URLSearchParams(params);
    const dcpCode = searchParams.get('dcpCode'); // Filter by subject (discipline code)
    const clsNo = searchParams.get('clsNo'); // Filter by class (Chinese Library Classification)
    if (dcpCode && clsNo) {
        throw new Error('dcpCode and clsNo cannot be used at the same time');
    }
    searchParams.set('pageSize', '100'); // Max page size. Any larger value will be ignored
    searchParams.set('page', '1');
    !dcpCode && !clsNo && searchParams.set('dcpCode', 'nolimit'); // No classification filter
    const url = `https://space.lib.buaa.edu.cn/meta-local/opac/new/100/${clsNo ? 'byclass' : 'bysubject'}?${searchParams.toString()}`;
    const { data } = await got(url);
    const list = (data?.data?.dataList || []) as Book[];
    const item = await Promise.all(list.map(async (item: Book) => await getItem(item)));
    const res: Data = {
        title: '北航图书馆 - 新书速递',
        item,
        description: '北京航空航天大学图书馆新书速递',
        language: 'zh-CN' as Language,
        link: 'https://space.lib.buaa.edu.cn/space/newBook',
        author: '北京航空航天大学图书馆',
        allowEmpty: true,
        image: 'https://lib.buaa.edu.cn/apple-touch-icon.png',
    };

View on GitHub (pinned to bed535e087)

Solutions

Supply at most one of dcpCode or clsNo in the path's query string.
Omit both to get the unfiltered feed (the handler sets dcpCode=nolimit for you).
Pick the scheme you want: dcpCode for subject/discipline, clsNo for CLC class.

Example fix

// before
//   /buaa/space/newbook/dcpCode=CS101/clsNo=TP311
// after  (subject filter only)
//   /buaa/space/newbook/dcpCode=CS101

Defensive patterns

Strategy: validation

Validate before calling

const params = new URLSearchParams(queryTail);
const dcpCode = params.get('dcpCode');
const clsNo = params.get('clsNo');
if (dcpCode && clsNo) {
  // reject early with a clear message before calling the route
  throw new Error('Choose either dcpCode (subject) or clsNo (CLC class), not both.');
}

Prevention

Parse the query tail once and assert mutual exclusivity up front.
Document that dcpCode and clsNo are alternatives, not combinable filters.

When it happens

Trigger: Calling the route with a path whose query string contains both `dcpCode` and `clsNo`, e.g. `/buaa/space/newbook/dcpCode=CS101/clsNo=TP311`.

Common situations: User concatenates two filter URLs thinking they combine; migrating from a bookmarked OPAC URL that carried both params; copy-paste of an exploratory search URL.

Related errors

AI-assisted analysis of DIYgod/RSSHub@bed535e087 (2026-08-12). Data as JSON: /api/errors/5a63e88b4be77ff9. Report an issue: GitHub.