Issue with `useParams` hook on unmounted component

[brandon-pereira]

Version

5.1.0

Test Case

https://codesandbox.io/s/jolly-field-rm0sb

Steps to reproduce

Use the children prop on a <Route /> to render a component.

Expected Behavior

Like with accessing match off of props, useParams() should return null or an empty object.

Actual Behavior

useParams errors when reading property off null.

[brandon-pereira]

To fix, update this line: https://github.com/ReactTraining/react-router/blob/0c058adc5b56c6d9b409af5e4d8330c645fac00c/packages/react-router/modules/hooks.js#L39 to

const match = useContext(Context).match
return match ? match.params : {}

I don't want to mess with the source, it seems there is a mixture between compiled and source code committed (or maybe I'm just crazy).

Also, more generally, does this return null or {}. I think useParams makes sense to always return an object so you don't need to check the response in the front end.

[timdorr]

That's the right place for it, so if you want to submit a PR, go right ahead!

[brandon-pereira]

@timdorr PR has been opened :)