Comments (5)
What about
type TestType =
| {
as: "link";
id: string;
}
| {
as: "div";
id?: undefined
};
from typescript.
Strictly speaking, this could be a breaking change when not implemented correctly. Based on this question on StackOverflow, JS discrimates between implicitly setting a property to undefined
vs. setting it implicitly as undefined
(by not defining it). So there is the possibility that this could be breaking, for example in this code:
type TestType = {
as: 'div';
id?: undefined;
}
const test = (props: TestType) => "id" in props;
// true
console.log(test({as: 'div', id: undefined}));
// false
console.log(test({as: 'div'}));
I don't have an idea to on how this could be implemented without breaking prior code. Im also not sure if the code above has actually been written before since I don't see how the code above could be useful.
from typescript.
What about
type TestType = | { as: "link"; id: string; } | { as: "div"; id?: undefined };
Lol, haven't thought of that, thanks for your comment. Maybe id?: never
would be even better.
Imo, this code doesn't express the intent as good as id: undefined
would, but I mean, it works. What do you guys think?
from typescript.
Maybe id?: never would be even better.
Yeah, if you want ts report error on test({as: 'div', id: undefined})
you can replace id?: undefined
with id?: never
and please make sure to turn on exactOptionalPropertyTypes: true
from typescript.
Alright, thanks alot @whzx5byb! Im gonna go ahead and close this feature-request since this would be a breaking change for a small (and arguable) improvement. Consider the solutions provided by whzx or me :) .
from typescript.
Related Issues (20)
- Scope confusion with reused signatures
- Declaration references expanded type paramater
- Design Meeting Notes, 3/29/2024
- Design Meeting Notes, 4/12/2024
- Design Meeting Notes, 4/16/2024
- Design Meeting Notes, 4/23/2024
- Design Meeting Notes, 4/26/2024 HOT 1
- Design Meeting Notes, 4/30/2024 HOT 1
- tsc --init update 2024 HOT 4
- [transpileDeclaration API][5.5] Type containing enum values is incorrectly emitted HOT 3
- 5.5 Beta - Error assigning const string to enum from another file HOT 3
- `export default` generates JavaScript and declaration file incompatible HOT 2
- Issues with `isolatedDeclarations` and the associated fixes in editor HOT 1
- Incremental Builds are not Reliable v5.4.5 HOT 2
- Design Meeting Notes, 5/3/2024 HOT 1
- [transpileDeclaration API][5.5] Type-only import is missing when type is used as arrow function argument HOT 3
- Error on types when using multiple conditional properties HOT 1
- Compiler Option to monitor external dependencies
- Extract interface metadata for runtime HOT 1
- Enum allows numeric keys with leading 0s HOT 5
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