DIYgod/RSSHub · warning · InvalidParameterError

Invalid community: ${community}

Error message

Invalid community: ${community}

What it means

Thrown by the lemmy route handler as InvalidParameterError when the `community` path param does not contain exactly one '@' — i.e. it is not in the required name@instance format. The handler splits on '@' and requires exactly 2 parts; any other count (0 or 2+ '@' signs) is rejected before any network call.

Source

Thrown at lib/routes/lemmy/index.ts:68

            },
        ],
        requirePuppeteer: false,
        antiCrawler: false,
        supportBT: false,
        supportPodcast: false,
        supportScihub: false,
    },
    name: 'Community',
    maintainers: ['wb14123', 'pseudoyu'],
    handler,
};

async function handler(ctx) {
    const sort = ctx.req.param('sort') ?? 'Active';
    const community = ctx.req.param('community');
    const communitySlices = community.split('@');
    if (communitySlices.length !== 2) {
        throw new InvalidParameterError(`Invalid community: ${community}`);
    }
    const instance = community.split('@', 2)[1];
    const allowedDomain = ['lemmy.world', 'lemm.ee', 'lemmy.ml', 'sh.itjust.works', 'feddit.de', 'hexbear.net', 'beehaw.org', 'lemmynsfw.com', 'lemmy.ca', 'programming.dev'];
    if (!config.feature.allow_user_supply_unsafe_domain && !allowedDomain.includes(new URL(`http://${instance}/`).hostname)) {
        throw new ConfigNotFoundError(`This RSS is disabled unless 'ALLOW_USER_SUPPLY_UNSAFE_DOMAIN' is set to 'true'.`);
    }

    const communityUrl = `https://${instance}/api/v3/community?name=${community}`;
    const communityData = await cache.tryGet(communityUrl, async () => {
        const result = await got({ method: 'get', url: communityUrl, headers: { 'Content-Type': 'application/json' } });
        return result.data.community_view.community;
    });

    const postUrl = `https://${instance}/api/v3/post/list?type_=All&sort=${sort}&community_name=${community}&limit=50`;
    const postData = await cache.tryGet(
        postUrl,
        async () => {
            const result = await got({ method: 'get', url: postUrl, headers: { 'Content-Type': 'application/json' } });

View on GitHub (pinned to bed535e087)

Solutions

1. Provide the community in name@instance form, e.g. /lemmy/programming@programming.dev/Hot
2. If you want a default instance, wrap the route or pre-process the param before calling the handler
3. Validate/normalize the param at the proxy layer for self-hosters
4. Check for URL-encoded '@' (%40) if the literal isn't coming through

Example fix

// before
const communitySlices = community.split('@');
if (communitySlices.length !== 2) {
    throw new InvalidParameterError(`Invalid community: ${community}`);
}
// after — clearer message + accept %40
const normalized = community.replaceAll('%40', '@');
const communitySlices = normalized.split('@');
if (communitySlices.length !== 2) {
    throw new InvalidParameterError(`Invalid community '${community}'. Expected format: name@instance (e.g. programming@programming.dev)`);
}

function parseCommunity(raw: string): { name: string; instance: string } {
  const norm = raw.replaceAll('%40', '@');
  const parts = norm.split('@');
  if (parts.length !== 2 || !parts[0] || !parts[1]) {
    throw new Error(`community '${raw}' must be name@instance`);
  }
  return { name: parts[0], instance: parts[1] };
}

function isCommunityFormat(v: unknown): v is string {
  if (typeof v !== 'string') return false;
  const parts = v.replaceAll('%40', '@').split('@');
  return parts.length === 2 && parts[0].length > 0 && parts[1].length > 0;
}

try { return await handler(ctx); }
catch (e) {
  if (e instanceof InvalidParameterError && /Invalid community/.test(e.message)) {
    return ctx.json({ error: e.message, format: 'name@instance' }, 400);
  }
  throw e;
}

When it happens

Trigger: Request to /lemmy/<community>/<sort> where <community> lacks the @instance suffix (e.g. 'programming' instead of 'programming@programming.dev'), or contains multiple '@' signs (e.g. 'a@b@c'). The split must yield exactly ['name','instance'].

Common situations: User omits the instance (most common — many users assume a default instance); copy-paste truncates the community name; URL encoding mangles the '@' (e.g. %40 handled differently); trailing slash creating an empty segment.

Related errors

• Bad timeRange range. See <a href="https://docs.rsshub.app/ro
• Bad parameter. See <a href="https://docs.rsshub.app/routes/g
• Invalid city
• Invalid channel name
• This category does not exist. Please refer to the documentat

AI-assisted analysis of DIYgod/RSSHub@bed535e087 (2026-08-12). Data as JSON: /api/errors/ec04b732d7d6776f. Report an issue: GitHub.