fix(Exact): support array union #421
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@JasonShin could you help review this PR? including grammar issues lol |
test-d/exact.ts
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| { // Spec - union of array with nested fields | ||
| type Type = Array<{x: string}> & Array<{z: number; d: {e: string}}>; |
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Thanks @zorji !! I was testing this again and found that union of 2 ReadOnlyArray breaks the type. But I think creating a union of 2 read-only arrays is already broken in TS...
Unless you think this is also important to handle in this PR 👍
| }]; | ||
| // @ts-expect-error | ||
| fn(input); | ||
| } |
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Possibly we can include more test coverages to check excess, exact, missing and mismatching fields for the union array test
source/exact.d.ts
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| */ | ||
| : {[Key in keyof ParameterType]: Exact<ParameterType[Key], InputType[Key]>} & Record<Exclude<keyof InputType, KeysOfUnion<ParameterType>>, never>; | ||
| export type Exact<ParameterType, InputType> = | ||
| // Converting union of array to array of union. i.e. A[] & B[] => (A & B)[] |
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Otherwise looks good, I will leave grammar and spelling checks to others 😊 |
| @@ -143,3 +143,69 @@ import type {Exact} from '../index'; | |||
| fn(input); | |||
| } | |||
| } | |||
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A little bit out of the scope of this PR but can we also include exhaustive tests against ReadonlyArray as well? I just want to ensure ReadonlyArray will work consistently in the future along with the regular mutable arrays.
We can just copy & paste Array spec for the ReadonlyArray test. I just quickly tested Array spec against ReadonlyArray and it seems to work fine
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@JasonShin looks like ReadOnly is an easy fix but I am not sure whether this is a breaking change. I'll put them in 2 separate PRs. https://github.com/zorji/type-fest/pull/1/files |
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@JasonShin actually I think I found a way |
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@sindresorhus Please review this thanks 👍 |
source/exact.d.ts
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| Return `never` if T is not an array. | ||
| It creates a type-safe way to access the element type of `unknown` type. | ||
| */ | ||
| type ArrayElement<T> = T extends readonly unknown[]? T[0] : never; |
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Could this use the trick mentioned in #118 (comment) ?
Co-authored-by: Sindre Sorhus <sindresorhus@gmail.com>
@sindresorhus I have tested and found the suggested implementation doesn't work for union of array |
Fixes #419