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Object.fromEntries loses all types on the key #49305
Description
lib Update Request
Configuration Check
My compilation target is es2020 and my lib is ES2020.
Missing / Incorrect Definition
fromEntries<T = any>(entries: Iterable<readonly [PropertyKey, T]>): { [k: string]: T };should be
fromEntries<K extends PropertyKey, T = any>(entries: Iterable<readonly [K, T]>): { [k in K]: T };Sample Code
enum Period {
M1 = '1m',
M3 = '3m',
M6 = '6m',
Y1 = '1y',
Y3 = '3y',
Y5 = '5y',
Y10 = '10y',
}
const list: [Period, moment.Moment][] = [
[Period.M1, moment().subtract(1, 'month')],
[Period.M3, moment().subtract(3, 'months')],
[Period.M6, moment().subtract(6, 'months')],
[Period.Y1, moment().subtract(1, 'year')],
[Period.Y3, moment().subtract(3, 'years')],
[Period.Y5, moment().subtract(5, 'years')],
[Period.Y10, moment().subtract(10, 'years')],
];
const object: { [k in Period]: moment.Moment } = Object.fromEntries(list);Returns error for object:
Type '{ [k: string]: Moment; }' is missing the following properties from type '{ "1m": Moment; "3m": Moment; "6m": Moment; "1y": Moment; "3y": Moment; "5y": Moment; "10y": Moment; }': "1m", "3m", "6m", "1y", and 3 more.ts(2740)
Documentation Link
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/fromEntries
Notes
I've read the soundness issues discussion on Object.keys(), but I'm not seeing how that should/would apply to Object.fromEntries().
Say if I am passing a [A, B][] into Object.fromEntries() where A is union of a class C and another enum D, I am going to get C.toString() | D. I am already hitting fromEntries(entries: Iterable<readonly any[]>): any; instead.
Activity
hfhchan commentedon May 30, 2022
See also: #37457 (comment)
I just noted that this doesn't work because it's possible to omit a particular row in
list, but the resulting type forObject.fromEntries()would generate an object that has all possiblePeriods as keys.Apparently
doesn't work either
hfhchan commentedon May 30, 2022
Essentially a duplicate of #35745 but that issue has been closed without resolution.
RyanCavanaugh commentedon May 31, 2022
It wouldn't be correct to do this, because the type of an array tells you want might be in it, not what is in it. For example,
listcould be entirely empty, which would makeobject's value be{ }, despite the type ofobjectsaying that it had aM1property.typescript-bot commentedon Jun 2, 2022
This issue has been marked 'Working as Intended' and has seen no recent activity. It has been automatically closed for house-keeping purposes.
lbfalvy commentedon Jan 9, 2024
Why not type it as
fromEntries<K, V>(entries: [K, V][]): {[k: K]?: V}?