import type { ExtensionParser, Schema, WriteMode } from '../../../schema/index.js';
import type { ParseAttrValueOptions } from './options.js';
export declare const defaultParseExtension: ExtensionParser<never>;
export declare const isRequired: (schema: Schema, mode: WriteMode) => boolean;
export declare const applyCustomValidation: (schema: Schema, inputValue: unknown, options?: ParseAttrValueOptions) => void;