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CustomEvent.detail is null when not defined #1585

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GauBen opened this issue Jun 29, 2023 · 3 comments · May be fixed by #1586
Open

CustomEvent.detail is null when not defined #1585

GauBen opened this issue Jun 29, 2023 · 3 comments · May be fixed by #1586

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@GauBen
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GauBen commented Jun 29, 2023

CustomEvent.detail is defined as follows:

interface CustomEvent<T = any> extends Event {
    readonly detail: T;

	// ...
}

Source:

TypeScript-DOM-lib-generator/inputfiles/overridingTypes.jsonc

Lines 538 to 540 in 957eced

"detail": {
"overrideType": "T"
}

This is slightly wrong as CustomEvent.detail defaults to null when not defined: Playground

The playground contains a fix I suggest: detail: T extends {} ? T : null

I'll open a PR referring to this issue
GauBen added a commit to GauBen/TypeScript-DOM-lib-generator that referenced this issue Jun 29, 2023
@GauBen
fix: updated CustomEvent.detail to be null when not defined
7639d7d 
Fixes microsoft#1585
This was referenced Jun 29, 2023
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Merged
@HolgerJeromin
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HolgerJeromin commented Jun 29, 2023 •
edited

What about this code?

new CustomEvent("myEvent", {  detail: false });

Edit: I am surprised but this seems to work with your PR, too.

JFYI: This is easier to debug in playground with instant type highlighting:

let A: RealDetailType<undefined>
//  ^?
let B: RealDetailType<void>
//  ^?
let C: RealDetailType<null>
//  ^?
let D: RealDetailType<string | undefined> 
//  ^?
let E: RealDetailType<boolean> 
//  ^?

@GauBen
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GauBen commented Jun 29, 2023

I didn't know about the ^? trick, thanks @HolgerJeromin!

I'm not sure to understand the problem with detail: false, as false is defined, new CustomEvent("e", { detail: false }).detail === false

@HolgerJeromin
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HolgerJeromin commented Jun 29, 2023 •
edited

I thought false would not qualify T extends {} so the result would be null instead of T. But, yes this worked.
Sorry for the noise :)

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fix: updated CustomEvent.detail to be null when not defined GauBen/TypeScript-DOM-lib-generator
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@HolgerJeromin @GauBen