@maplibre/maplibre-gl-style-spec/src/validate/validate_property.ts

a specification for maplibre styles

import {ValidationError} from '../error/validation_error';
import {getType} from '../util/get_type';
import {isFunction} from '../function';
import {unbundle, deepUnbundle} from '../util/unbundle_jsonlint';
import {supportsPropertyExpression} from '../util/properties';

export function validateProperty(options, propertyType) {
    const key = options.key;
    const validateSpec = options.validateSpec;
    const style = options.style;
    const styleSpec = options.styleSpec;
    const value = options.value;
    const propertyKey = options.objectKey;
    const layerSpec = styleSpec[`${propertyType}_${options.layerType}`];

    if (!layerSpec) return [];

    const transitionMatch = propertyKey.match(/^(.*)-transition$/);
    if (
        propertyType === 'paint' &&
        transitionMatch &&
        layerSpec[transitionMatch[1]] &&
        layerSpec[transitionMatch[1]].transition
    ) {
        return validateSpec({
            key,
            value,
            valueSpec: styleSpec.transition,
            style,
            styleSpec
        });
    }

    const valueSpec = options.valueSpec || layerSpec[propertyKey];
    if (!valueSpec) {
        return [new ValidationError(key, value, `unknown property "${propertyKey}"`)];
    }

    let tokenMatch;
    if (
        getType(value) === 'string' &&
        supportsPropertyExpression(valueSpec) &&
        !valueSpec.tokens &&
        (tokenMatch = /^{([^}]+)}$/.exec(value))
    ) {
        return [
            new ValidationError(
                key,
                value,
                `"${propertyKey}" does not support interpolation syntax\n` +
                    `Use an identity property function instead: \`{ "type": "identity", "property": ${JSON.stringify(tokenMatch[1])} }\`.`
            )
        ];
    }

    const errors = [];

    if (options.layerType === 'symbol') {
        if (
            propertyKey === 'text-font' &&
            isFunction(deepUnbundle(value)) &&
            unbundle(value.type) === 'identity'
        ) {
            errors.push(
                new ValidationError(key, value, '"text-font" does not support identity functions')
            );
        }
    }

    return errors.concat(
        validateSpec({
            key: options.key,
            value,
            valueSpec,
            style,
            styleSpec,
            expressionContext: 'property',
            propertyType,
            propertyKey
        })
    );
}