/**
 * Returns the value for `key` from `map`, creating and inserting it via
 * `makeDefault` if absent.
 */
export declare function getOrCreate<K, V>(map: Map<K, V>, key: K, makeDefault: () => V): V;
/**
 * Returns a copy of `source` with every `undefined`-valued key removed.
 *
 * Entities in this library must never carry a key holding `undefined`. Two
 * things go wrong when they do. `entityChecksum` includes a field only when
 * the key is present, so clearing an app-level field by assigning `undefined`
 * would leave the entity hashing as though it were still set — and clearing has
 * to be exactly reversible. And `"field" in entity` becomes true, so any
 * downstream mapper that turns `undefined` into `null` flips the field from
 * absent to present, which moves the checksum of every entity of that kind.
 *
 * Applies wherever caller-supplied fields are spread into an entity: the
 * `setExtras` pair on both engines, and the parser's `map*` extension hooks.
 */
export declare function withoutUndefinedValues(source: Record<string, unknown>): Record<string, unknown>;
/** Returns a shallow-copied array of items sorted by `id` in lexicographic order. */
export declare function sortedCopyById<T extends {
    id: string;
}>(items: T[]): T[];
/** Deduplicates and sorts an iterable of strings. */
export declare function sortedUnique(values: Iterable<string>): string[];
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