perspective-dev/perspective · error · TypeError

TileSourceSpec. must be a positive number

Error message

TileSourceSpec.${key} must be a positive number

What it means

The local helper num(key, dflt) inside parseTileSourceSpec validates optional numeric fields (tile_size, max_zoom): missing keys fall back to the default, but any present value must be a finite positive number. Zero, negative values, NaN, Infinity, or non-numbers (e.g. "256" as a string from JSON) trigger this TypeError.

Solutions

1. Pass the field as a real number (tile_size: 256), not a numeric string
2. Remove non-positive or non-finite values; omit the key to accept the documented default
3. Coerce/validate JSON input with Number() before registering the spec

When it happens

Trigger: Thrown at packages/viewer-charts/src/ts/map/tile-source.ts:182 when the library encounters an invalid state.

Common situations: See trigger scenarios.

AI-assisted analysis of perspective-dev/perspective@11c8238c0c (2026-09-09). Data as JSON: /api/errors/220bbeabb7146833. Report an issue: GitHub.

Appendix: source

Thrown at packages/viewer-charts/src/ts/map/tile-source.ts:182

            "TileSourceSpec.subdomains must be an array of non-empty strings",
        );
    }

    const subdomains = Object.freeze([...rawSubdomains] as string[]);
    if (template.includes("{s}") && subdomains.length === 0) {
        throw new TypeError(
            'TileSourceSpec.template uses "{s}" but no subdomains were given',
        );
    }

    const num = (key: string, dflt: number): number => {
        const v = raw[key];
        if (v === undefined) {
            return dflt;
        }

        if (typeof v !== "number" || !Number.isFinite(v) || v <= 0) {
            throw new TypeError(
                `TileSourceSpec.${key} must be a positive number`,
            );
        }

        return v;
    };

    return Object.freeze({
        id,
        label,
        template,
        subdomains,
        attribution,
        tile_size: num("tile_size", 256),
        max_zoom: num("max_zoom", 19),
    });
}

View on GitHub (pinned to 11c8238c0c)