[utils] Improve type inference of useForkRef #31845
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eps1lon
commented
Mar 16, 2022
| @@ -72,7 +72,7 @@ function useSelect<TValue>(props: UseSelectParameters<TValue>) { | |||
| } | |||
| }, [listboxFocusRequested]); | |||
|
|
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| const updateListboxRef = (listboxElement: HTMLUListElement) => { | |||
| const updateListboxRef = (listboxElement: HTMLUListElement | null) => { | |||
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We would basically need to always add | null when using ref callbacks no?
eps1lon
commented
Mar 16, 2022
| @@ -154,7 +154,7 @@ const Link = React.forwardRef(function Link(inProps, ref) { | |||
| as={component} | |||
| onBlur={handleBlur} | |||
| onFocus={handleFocus} | |||
| ref={handlerRef} | |||
| ref={handleRef} | |||
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Just a typo-drive-by-fix
eps1lon
commented
Mar 16, 2022
| @@ -115,7 +115,7 @@ const Link = React.forwardRef(function Link(inProps, ref) { | |||
| ref: focusVisibleRef, | |||
| } = useIsFocusVisible(); | |||
| const [focusVisible, setFocusVisible] = React.useState<boolean>(false); | |||
| const handlerRef = useForkRef(ref, focusVisibleRef) as React.RefObject<HTMLSpanElement>; | |||
| const handleRef = useForkRef(ref, focusVisibleRef) as React.Ref<HTMLSpanElement>; | |||
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Cast was unsound generally but also technically incorrect at runtime. useForkRef returns a function not an object (though the specific implementation is irrelevant. What's import is, that it's a generic ref).
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eps1lon
commented
Mar 16, 2022
| export default function useForkRef<InstanceA, InstanceB>( | ||
| refA: React.Ref<InstanceA> | null | undefined, | ||
| refB: React.Ref<InstanceB> | null | undefined, | ||
| ): React.Ref<InstanceA & InstanceB> | null { |
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This helps TypeScript with inference with the proposed changes in DefinitelyTyped/DefinitelyTyped#58936.
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Nice, this will basically create a union of the two in case they are different 👍
mnajdova
approved these changes
Mar 22, 2022
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Currently instances in ref callbacks are allowed to be nullable due to our bivariance hack. However, during runtime these instances can be null: https://codesandbox.io/s/refs-are-nullable-m44vxx
We'll likely remove the bivariance hack to catch these issues in the future. In the meantime, existing packages and tests should guard against nullable instances regardless.
The issue was first reported in DefinitelyTyped/DefinitelyTyped#58464