Intl types: Better typing for exactOptionalPropertyTypes needed

Bug Report

I did not find a "planning" issue for related issues.
All delivered types should be safe to use with the new Typescript option.

🕗 Version & Regression Information

I was unable to test this on prior versions because this is a new option

⏯ Playground Link

// @exactOptionalPropertyTypes
const IntlOptions: Intl.DateTimeFormatOptions = {
    timeZone: undefined
};

Workbench Repro

🙁 Actual behavior

Type 'undefined' is not assignable to type 'string'.(2322)

🙂 Expected behavior

Should compile because undefined is a valid property for that object.
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Intl/DateTimeFormat/DateTimeFormat

copied from microsoft/TypeScript-DOM-lib-generator#1126

I'm half-half on this, undefined is the default for those values, yes, but it's not documented as something you should really pass in via that MDN page - can you think of a specific reason why we should add this?

My real world code is something like that:

let timeZone: string | undefined = getUserTimeZone();
let IntlOptions: Intl.DateTimeFormatOptions = {
     timeZone: timeZone
};

refactoring to

let timeZone: string | undefined = getUserTimeZone();
let IntlOptions: Intl.DateTimeFormatOptions = {};
if (timeZone) {
    IntlOptions.timeZone = timeZone;
}

to make TS happy feels clumsy.
My API returns "use client setting" explicit as undefined (for timezone and locale) to allow direct use in the modern browser APIs.

Yeah, that seems reasonable to me

Allow undefined in Intl inputs to allow for ergonomic usage of exactO…

I would love if the setting of undefined would simply delete the key in the object...i.e. set it to the default of timeZone?

I would love if the setting of undefined would simply delete the key in the object...i.e. set it to the default of timeZone?

Seems like you just want exactOptionalPropertyTypes: false then.

I would love if the setting of undefined would simply delete the key in the object...i.e. set it to the default of timeZone?

Seems like you just want exactOptionalPropertyTypes: false then.

Is it? I was under the impression that 2 != 3? (But it is more about category then arithmetics)

when: exactOptionalPropertyTypes: false

timeZone can be not set
timeZone: can be string
timeZone can be undefined

exactOptionalPropertyTypes: true

timeZone can be not set, but you can not get here back by yourself.
timeZone: can be string
~~3) timeZone can be undefined~~

I am asking for a 3rd way: where you can unset the value or it holds value of specific type... so we can still use the ? optional bit on the type but in this stricter way...
We might need some other annotation like it can not be unset maybe a +?

Maybe I'm also confused, but point is seems to be what this issue is about. The change would allow all three options by adding | undefined in the .d.ts which you can see in orta@689bf6f

Marcin Tolysz (@tolysz)

Marcin Tolysz (@tolysz)

// exactOptionalPropertyTypes: true
foo.optional = undefined;  // error
delete foo.optional;  // all good

Intl 2021 Updates (#45647)

This is included with #45647 👍🏻

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Intl types: Better typing for exactOptionalPropertyTypes needed #45652

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Intl types: Better typing for exactOptionalPropertyTypes needed #45652

Description

Bug Report

🕗 Version & Regression Information

⏯ Playground Link

🙁 Actual behavior

🙂 Expected behavior

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orta commented on Aug 31, 2021

HolgerJeromin commented on Aug 31, 2021

orta commented on Aug 31, 2021

tolysz commented on Aug 31, 2021

nmain commented on Aug 31, 2021

tolysz commented on Sep 1, 2021

orta commented on Sep 1, 2021

fatcerberus commented on Sep 2, 2021

orta commented on Sep 8, 2021

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