DIYgod/RSSHub · warning · InvalidParameterError

Invalid category: ${categoryParam}. Valid categories are: ${

Error message

Invalid category: ${categoryParam}. Valid categories are: ${Object.keys(CATEGORY_SLUG_TO_ID).join(', ')}

What it means

InvalidParameterError thrown by the baselang blog route when an optional :category parameter is supplied but not a key of CATEGORY_SLUG_TO_ID. The route lowercases the param first, then checks Object.hasOwn, so the error lists all valid slugs.

Source

Thrown at lib/routes/baselang/index.ts:81

    },
    radar: [
        {
            source: ['baselang.com/blog', 'baselang.com/blog/:category'],
            target: '/blog/:category',
        },
    ],
    name: 'Blog',
    maintainers: ['johan456789'],
    handler,
};

async function handler(ctx: Context): Promise<Data> {
    const categoryParam = (ctx.req.param('category') ?? '').toLowerCase();
    logger.debug(`BaseLang: received request, category='${categoryParam || 'all'}'`);

    if (categoryParam && !Object.hasOwn(CATEGORY_SLUG_TO_ID, categoryParam)) {
        logger.debug(`BaseLang: invalid category '${categoryParam}'`);
        throw new InvalidParameterError(`Invalid category: ${categoryParam}. Valid categories are: ${Object.keys(CATEGORY_SLUG_TO_ID).join(', ')}`);
    }

    const searchParams: string[] = ['per_page=20', '_embed=author,wp:term'];
    if (categoryParam) {
        const id = CATEGORY_SLUG_TO_ID[categoryParam];
        searchParams.push(`categories=${id}`);
    }

    const apiUrl = `${API_BASE}/posts?${searchParams.join('&')}`;

    const data = await ofetch<WordpressPost[]>(apiUrl);
    logger.debug(`BaseLang: fetched ${data.length} posts`);

    const items = data.map((post) => ({
        title: post.title?.rendered,
        description: post.content?.rendered ?? post.excerpt?.rendered ?? '',
        link: post.link,
        pubDate: parseDate(post.date_gmt ?? post.date),

View on GitHub (pinned to bed535e087)

Solutions

Use one of the slugs in the error message (advanced-grammar, basic-grammar, company, confidence, french, humor, medellin, motivation, pronunciation, study-tips, success-stories, travel, uncategorized, vocabulary), or omit the category.
If the WordPress site has a new category, find its WP term id and add it to CATEGORY_SLUG_TO_ID.

Defensive patterns

Strategy: validation

Validate before calling

const categoryParam = (ctx.req.param('category') ?? '').toLowerCase();
if (categoryParam && !Object.hasOwn(CATEGORY_SLUG_TO_ID, categoryParam)) {
    throw new InvalidParameterError(`Invalid category: ${categoryParam}. Valid: ${Object.keys(CATEGORY_SLUG_TO_ID).join(', ')}`);
}

Type guard

function isKnownCategory(slug: string): slug is keyof typeof CATEGORY_SLUG_TO_ID {
    return Object.prototype.hasOwnProperty.call(CATEGORY_SLUG_TO_ID, slug);
}

Prevention

Lowercase the param before lookup so case variants do not fail.
Expose CATEGORY_OPTIONS via parameters.options so valid slugs are discoverable.

When it happens

Trigger: Calling /baselang/blog/:category with a slug not in CATEGORY_SLUG_TO_ID (e.g. 'news', 'spanish', or a typo). Omitting category is fine and returns all posts.

Common situations: User guesses a slug that the WordPress site uses but the route never mapped; case differences are already handled by toLowerCase, so this usually means a genuinely unmapped category.

Related errors

AI-assisted analysis of DIYgod/RSSHub@bed535e087 (2026-08-12). Data as JSON: /api/errors/07318529ac5c630e. Report an issue: GitHub.