perspective-dev/perspective · error · TypeError

TileSourceSpec. must be a non-empty string

Error message

TileSourceSpec.${key} must be a non-empty string

What it means

Generic string-field guard inside parseTileSourceSpec: the local helper str(key) throws this TypeError whenever a required string field (id, label, template, or attribution) of the tile source spec is missing, not a string, or an empty string. The interpolated key identifies which field failed.

Solutions

1. Supply a non-empty string for the field named in the message
2. Check for undefined fields from incomplete JSON definitions of the tile source
3. Default-check required fields before calling registerTileSource

When it happens

Trigger: Thrown at packages/viewer-charts/src/ts/map/tile-source.ts:138 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/3bc5063d12c92eb0. Report an issue: GitHub.

Appendix: source

Thrown at packages/viewer-charts/src/ts/map/tile-source.ts:138

    /** See {@link TileSource.maxZoom}. Default 19. */
    readonly max_zoom: number;
}

/**
 * Validate + normalize an untrusted spec (a JSON entry or a
 * `registerTileSource` argument). Throws `TypeError` naming the
 * offending field; returns a frozen spec with defaults applied.
 */
export function parseTileSourceSpec(input: unknown): TileSourceSpec {
    if (typeof input !== "object" || input === null) {
        throw new TypeError("TileSourceSpec must be an object");
    }

    const raw = input as Record<string, unknown>;
    const str = (key: string): string => {
        const v = raw[key];
        if (typeof v !== "string" || v.length === 0) {
            throw new TypeError(
                `TileSourceSpec.${key} must be a non-empty string`,
            );
        }

        return v;
    };

    const id = str("id");
    const label = str("label");
    const template = str("template");
    const attribution = str("attribution");
    for (const placeholder of ["{z}", "{x}", "{y}"]) {
        if (!template.includes(placeholder)) {
            throw new TypeError(
                `TileSourceSpec.template must contain "${placeholder}"`,
            );
        }
    }

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