86 lines
1.8 KiB
TypeScript
86 lines
1.8 KiB
TypeScript
import type {Except} from './except';
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import type {RequiredKeysOf} from './required-keys-of';
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import type {Simplify} from './simplify';
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type SpreadObject<FirstType extends object, SecondType extends object> = {
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[Key in keyof FirstType]: Key extends keyof SecondType
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? FirstType[Key] | Required<SecondType>[Key]
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: FirstType[Key];
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} & Pick<
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SecondType,
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RequiredKeysOf<SecondType> | Exclude<keyof SecondType, keyof FirstType>
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>;
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type TupleOrArray = readonly [...unknown[]];
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type SpreadTupleOrArray<
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FirstType extends TupleOrArray,
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SecondType extends TupleOrArray,
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> = Array<FirstType[number] | SecondType[number]>;
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type Spreadable = object | TupleOrArray;
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/**
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Mimic the type inferred by TypeScript when merging two objects or two arrays/tuples using the spread syntax.
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@example
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```
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import type {Spread} from 'type-fest';
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type Foo = {
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a: number;
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b?: string;
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};
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type Bar = {
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b?: number;
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c: boolean;
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};
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const foo = {a: 1, b: '2'};
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const bar = {c: false};
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const fooBar = {...foo, ...bar};
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type FooBar = Spread<Foo, Bar>;
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// type FooBar = {
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// a: number;
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// b?: string | number | undefined;
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// c: boolean;
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// }
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const baz = (argument: FooBar) => {
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// Do something
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}
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baz(fooBar);
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```
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@example
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```
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import type {Spread} from 'type-fest';
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const foo = [1, 2, 3];
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const bar = ['4', '5', '6'];
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const fooBar = [...foo, ...bar];
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type FooBar = Spread<typeof foo, typeof bar>;
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// FooBar = (string | number)[]
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const baz = (argument: FooBar) => {
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// Do something
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};
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baz(fooBar);
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```
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@category Object
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*/
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export type Spread<
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FirstType extends Spreadable,
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SecondType extends Spreadable,
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> = FirstType extends TupleOrArray
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? SecondType extends TupleOrArray
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? SpreadTupleOrArray<FirstType, SecondType>
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: Simplify<SpreadObject<FirstType, SecondType>>
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: Simplify<SpreadObject<FirstType, SecondType>>;
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