Treat struct properties that have type undefined as optional #639
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thewilkybarkid
commented
Apr 1, 2022
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| type Identity<T> = T | ||
| type Merge<T> = T extends any ? Identity<{ [k in keyof T]: T[k] }> : never |
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thewilkybarkid
commented
Apr 1, 2022
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| type UndefinedProperties<T> = { | ||
| [P in keyof T]-?: undefined extends T[P] ? P : never | ||
| }[keyof T] | ||
| type ToOptional<T> = Merge<Pick<T, Exclude<keyof T, UndefinedProperties<T>>> & Partial<Pick<T, UndefinedProperties<T>>>> |
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Based on microsoft/TypeScript#12400 (comment)
thewilkybarkid
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Apr 1, 2022
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| // $ExpectType Codec<unknown, { _tag: "A"; a: string; } | { _tag: "B"; b: number; }, { _tag: "A"; a: string; } | { _tag: "B"; b: number; }> | ||
| // $ExpectType Codec<unknown, { a: string; _tag: "A"; } | { b: number; _tag: "B"; }, { a: string; _tag: "A"; } | { b: number; _tag: "B"; }> |
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Wasn't expecting these to be reordered.
|
I'm going to close this in favour of gcanti/fp-ts#1693. |
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This is an attempt to fix #628 (comment), by making properties in a
structthat can haveundefinedas a value optional.This feels quite thorny to do, and this is probably incomplete (e.g.
Schemeable?).