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

a specification for maplibre styles

import {ValidationError} from '../error/validation_error';

import {createExpression, createPropertyExpression} from '../expression';
import {deepUnbundle} from '../util/unbundle_jsonlint';

import {
    isFeatureConstant,
    isGlobalPropertyConstant,
    isStateConstant
} from '../expression/compound_expression';

import {Expression} from '../expression/expression';

export function validateExpression(options: any): Array<ValidationError> {
    const expression = (
        options.expressionContext === 'property' ? createPropertyExpression : createExpression
    )(deepUnbundle(options.value), options.valueSpec);
    if (expression.result === 'error') {
        return expression.value.map((error) => {
            return new ValidationError(`${options.key}${error.key}`, options.value, error.message);
        });
    }

    const expressionObj: Expression =
        (expression.value as any).expression ||
        (expression.value as any)._styleExpression.expression;

    if (
        options.expressionContext === 'property' &&
        options.propertyKey === 'text-font' &&
        !expressionObj.outputDefined()
    ) {
        return [
            new ValidationError(
                options.key,
                options.value,
                `Invalid data expression for "${options.propertyKey}". Output values must be contained as literals within the expression.`
            )
        ];
    }

    if (
        options.expressionContext === 'property' &&
        options.propertyType === 'layout' &&
        !isStateConstant(expressionObj)
    ) {
        return [
            new ValidationError(
                options.key,
                options.value,
                '"feature-state" data expressions are not supported with layout properties.'
            )
        ];
    }

    if (options.expressionContext === 'filter' && !isStateConstant(expressionObj)) {
        return [
            new ValidationError(
                options.key,
                options.value,
                '"feature-state" data expressions are not supported with filters.'
            )
        ];
    }

    if (options.expressionContext && options.expressionContext.indexOf('cluster') === 0) {
        if (!isGlobalPropertyConstant(expressionObj, ['zoom', 'feature-state'])) {
            return [
                new ValidationError(
                    options.key,
                    options.value,
                    '"zoom" and "feature-state" expressions are not supported with cluster properties.'
                )
            ];
        }
        if (options.expressionContext === 'cluster-initial' && !isFeatureConstant(expressionObj)) {
            return [
                new ValidationError(
                    options.key,
                    options.value,
                    'Feature data expressions are not supported with initial expression part of cluster properties.'
                )
            ];
        }
    }

    return [];
}