react-hooks/exhaustive-deps and useMemo(() => x, x)

I would like to memoize an array using `useMemo(() => x, x)`, where x.length is unknown but constant, and so think I have a legitimate use case to be able to disable the eslint warnings. I can find similar issues to this, including https://github.com/facebook/react/issues/18229#issuecomment-619569632, but not one where the length of the dependencies is unknown but constant. This code creates a warning > React Hook useMemo has a missing dependency: 'x'. Either include it or remove the dependency array. and > React Hook useMemo was passed a dependency list that is not an array literal. This means we can't statically verify whether you've passed the correct dependencies. Which links to an issue with the following comment > If you ... aren't sure your case is legit, file a new issue. https://github.com/facebook/react/issues/14920#issuecomment-472018817 My use case, without the useMemo, is as follows: ```ts /** * When an array in `arrays` goes from length 0 to length > 0, call `callback` */ export const useCallbackWhenAnArrayPopulates = ( callback: () => void, ...arrays: (readonly unknown[])[], ) => { // const memoArrays = useMemo(() => arrays, arrays); const prevArrays = useRef(arrays); useEffect(() => { if (prevArrays.current.length !== arrays.length) { throw 'Unexpected array length change in useCallbackWhenArraysPopulate'; } if ( prevArrays.current.some( (value, index) => !value.length && arrays[index]?.length, ) ) { callback(); } prevArrays.current = arrays; }, [arrays, callback]); }; ``` I would like to memoise `arrays`, which comes from spreading arguments passed to the hook, so that the useEffect is only called when one of these arguments changes. Ideally I'd do this with `useMemo(() => arrays, arrays)`. I know that [the dependency length for useMemo can't change](https://github.com/facebook/react/issues/18229), but though it's length is unknown, I would not expect it to change and prevent thi…