jackwener/OpenCLI · error · ArgumentError

--days must be an integer between 1 and 3 (wttr.in caps the

Error message

--days must be an integer between 1 and 3 (wttr.in caps the free-tier forecast at 3 days)

What it means

This ArgumentError is thrown by the wttr forecast command when the --days option is not an integer in the 1-3 range. The wttr.in free-tier API only serves a 3-day forecast payload, so requesting more than 3 days is impossible and requesting 0 or non-integer values is meaningless. The library fails fast client-side before making any network request.

Source

Thrown at clis/wttr/forecast.js:41

        },
        {
            name: 'days',
            type: 'int',
            default: 3,
            help: 'Max forecast days (1-3, wttr.in caps the response at 3 days)',
        },
    ],
    columns: [
        'rank', 'date', 'minTempC', 'maxTempC', 'avgTempC',
        'minTempF', 'maxTempF', 'avgTempF',
        'sunHour', 'totalSnowCm', 'uvIndex',
        'description', 'sunrise', 'sunset',
    ],
    func: async (args) => {
        const location = requireString(args.location, 'location');
        const days = Number(args.days ?? 3);
        if (!Number.isInteger(days) || days < 1 || days > 3) {
            throw new ArgumentError('--days must be an integer between 1 and 3 (wttr.in caps the free-tier forecast at 3 days)');
        }
        const body = await wttrFetch(location, 'wttr forecast');
        const list = Array.isArray(body?.weather) ? body.weather : [];
        if (!list.length) {
            throw new EmptyResultError('wttr forecast', `wttr.in returned no forecast for "${location}".`);
        }
        return list.slice(0, days).map((day, i) => {
            // wttr.in's day-summary uses the noon hourly slot for "main" description.
            // Index 4 = 12:00 in their 3-hour-step hourly array.
            const noon = Array.isArray(day.hourly) && day.hourly[4] ? day.hourly[4] : day.hourly?.[0] ?? {};
            const astro = Array.isArray(day.astronomy) ? day.astronomy[0] : null;
            return {
                rank: i + 1,
                date: day.date ?? null,
                minTempC: day.mintempC != null ? Number(day.mintempC) : null,
                maxTempC: day.maxtempC != null ? Number(day.maxtempC) : null,
                avgTempC: day.avgtempC != null ? Number(day.avgtempC) : null,
                minTempF: day.mintempF != null ? Number(day.mintempF) : null,

View on GitHub (pinned to 49907e53dc)

Solutions

Pass an integer between 1 and 3, e.g. --days 3
If you need longer ranges, use a different API (wttr.in free tier caps at 3 days)
Default to omitting --days, which defaults to 3

Example fix

// before
const days = Number(args.days ?? 3); // days=7 -> ArgumentError
// after
const days = Math.min(3, Math.max(1, Number.parseInt(args.days ?? 3, 10)));

Defensive patterns

Strategy: validation

Validate before calling

const days = Number(args.days ?? 3);
if (!Number.isInteger(days) || days < 1 || days > 3) {
  throw new Error('--days must be an integer between 1 and 3');
}

Type guard

function isValidDays(v) {
  const n = Number(v ?? 3);
  return Number.isInteger(n) && n >= 1 && n <= 3;
}

Try / catch

try {
  result = await forecast({ location, days });
} catch (err) {
  if (err instanceof ArgumentError) {
    console.error(`Invalid --days: ${err.message}`);
  } else throw err;
}

Prevention

Clamp user input to 1-3 with Math.min/Math.max before passing
Parse with parseInt and validate Number.isInteger
Document the 3-day free-tier cap in your CLI help text

When it happens

Trigger: Calling the forecast command with days < 1, days > 3, or a non-integer (e.g. '2.5', 'abc', ''). Number(args.days ?? 3) coerces strings, so '--days abc' becomes NaN and '--days 10' passes the truthiness check but fails the range test.

Common situations: Users assuming wttr.in supports 7-day forecasts like other weather APIs; scripts passing an unset or misparsed env var into --days; passing a float from a config file.

Related errors

AI-assisted analysis of jackwener/OpenCLI@49907e53dc (2026-08-29). Data as JSON: /api/errors/117e440b22e06d62. Report an issue: GitHub.