import type { Paths, UnknownRecord } from 'type-fest';
type MergedType<A, B> = A extends UnknownRecord ? B extends UnknownRecord ? A & B : MergedArray<A, B> : MergedArray<A, B>;
type MergedArray<A, B> = A extends any[] ? B extends any[] ? Array<A[number] | B[number]> : keyof B extends `${number}` ? Array<A[number] | B[keyof B]> : B : B;
/**
 * deep merge an object
 * @param source default object if no additional property is supplied
 * @param target properties to be merged with the default
 * @returns merged object
 */
export declare function merge<S, T, R = MergedType<S, T>>(source: S, target?: T): R;
/**
 * merge an array with any value
 * @param source the source array to be merged
 * @param target new replacement
 * @returns merged value
 */
export declare function mergeArray<S, T>(source: S[], target?: T): MergedArray<S[], T>;
/**
 * merge two arrays
 * @param source the source array to be merged
 * @param target new replacement
 * @returns merged array
 */
export declare function mergeArrays<S, T>(source: S[], target: T[]): MergedArray<S[], T[]>;
/**
 * annotate an array for key-based merging during preset resolution
 * @param key the property name used to identify matching elements across arrays
 * @param items the array of objects to annotate
 * @returns a shallow copy of the array with a non-enumerable merge key annotation
 */
export declare function mergeByKey<T extends Record<string, unknown>, K extends string & Paths<T, {
    bracketNotation: true;
    leavesOnly: true;
}>>(key: K, items: T[]): T[];
/**
 * merge an object with any value
 * @param source the source object to be merged
 * @param target new replacement
 * @returns merged value
 */
export declare function mergeObject<S extends {}, T>(source: S, target?: T): MergedType<S, T>;
export {};
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