type-plus/esm/merge.d.ts

Provides additional types for TypeScript.

import type { NonComposableTypes } from './composable_types.js';
import type { AnyRecord } from './object/AnyRecord.js';
import type { IsDisjoint } from './object/IsDisjoint.js';
import type { KeyTypes } from './object/KeyTypes.js';
import type { OptionalKeys } from './object/OptionalKeys.js';
import type { Properties } from './object/properties.js';
import type { IsLiteral } from './predicates/literal.js';
/**
 * Left join type `A` with type `B`.
 *
 * It handles cases like A or B are `Record`,
 * joining between required and optional props, etc.
 */
export type Merge<A, B> = [A, B] extends [NonComposableTypes, unknown] ? B : [A, B] extends [unknown, NonComposableTypes] ? A : A extends AnyRecord ? B extends AnyRecord ? IsDisjoint<A, B> extends true ? A & B : ([keyof A, keyof B] extends [infer KA extends KeyTypes, infer KB extends KeyTypes] ? (IsLiteral<KA> extends true ? (IsLiteral<KB> extends true ? ([OptionalKeys<A>, OptionalKeys<B>] extends [infer PKA extends KeyTypes, infer PKB extends KeyTypes] ? {
    [k in PKA & PKB]?: A[k] | B[k] | undefined;
} & {
    [k in Exclude<KA & KB, PKA | PKB>]: Merge.JoinProps<A[k], B[k]>;
} & {
    [k in Exclude<KA, PKA | KB>]: A[k];
} & {
    [k in Exclude<KB, PKB>]: B[k];
} & {
    [k in Exclude<KA & PKB, PKA>]: Exclude<A[k] | Partial<B[k]>, undefined>;
} : never) : Properties<{
    [k in Exclude<KA, KA & KB>]: A[k];
} & {
    [k in Exclude<KB, KA & KB>]: B[k];
} & {
    [k in KA & KB]: A[k] | B[k];
}>) : (IsLiteral<KB> extends true ? {
    [k in Exclude<KA, KB>]: A[k];
} & {
    [k in keyof B]: B[k];
} : {
    [k in Exclude<KA, KA & KB>]: A[k];
} & {
    [k in Exclude<KB, KA & KB>]: B[k];
} & {
    [k in KA & KB]: A[k] | B[k];
})) : never) : never : never;
export declare namespace Merge {
    type JoinProps<A, B> = A extends NonComposableTypes ? B : (B extends NonComposableTypes ? A : A & B);
}
/**
* Left join `a` with `b`.
*
* This returns the proper type of `{ ...a, ...b }`
*
* @example
* ```ts
* leftJoin({ a: 1 }, {} as { a?: string | undefined }) // { a: number | string }
* ```
*/
export declare function merge<A, B>(a: A, b: B): Merge<A, B>;
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