microsoft / microsoft/TypeScript
No validation in JSX when using template string index signatures
@ahejlsberg is already working on this.
Since Jun 29, 2021.
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Description
Here's the shortest example:
import * as React from "react";
interface Props {
foo: string;
bar: number;
[dataProp: `data-${string}`]: string;
}
function Yadda(props: Props) {
return <div />;
}
let props: Props = {
foo: "",
bar: 0,
"data-yadda": 42,
};
let x = <Yadda foo="hello" bar={42} data-yadda={42} />;
Expected: TypeScript should error on data-yadda, just as if we had explicitly declared a data-yadda property in Props, or if we had used a string index signature.
Actual: JSX dashed properties are exempt from these checks on the target object if a corresponding property doesn't exist.
My expectation is that if an index signature exists, and a property should be covered by that index signature, then TypeScript should check that the property is compatible with that index signature.
Here's a longer example that could be used in tests.
import * as React from "react";
interface Props {
foo: string;
bar: number;
[dataProp: `data-${string}`]: string;
}
function Yadda(props: Props) {
return <div />;
}
// Errors as expected on data-yadda. ✅
let propsObj1: Props = {
foo: "",
bar: 0,
"data-yadda": 42,
};
// Should error on data-yadda, does not. ❌
let x = <Yadda foo="hello" bar={42} data-yadda={42} />;
/////////
let propsObj2 = {
foo: "",
bar: 0,
"data-yadda": 42,
};
// Should error on data-yadda, does not. ❌
let y = <Yadda {...propsObj2} />
// Errors as expected on data-yadda. ✅
propsObj1 = propsObj2;
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