Destroy component on multiple rerenders

[jgbowser]

This is a fix for #185

the problem was rerender creates a newComponent, but only ever checks for and destroys the originally rendered component. Resolved this by reassigning component with the new, rerendered component so it always gets checked and destroyed when it should be.

Also adds a test case for multiple rerenders.

Thanks!

[yanick]

Looks good!

[yanick]

I'll be wild and assume that since no-one said anything so far, that's it's good and mashing that 'merge' button is totally okay. 😁

[github-actions]

🎉 This PR is included in version 3.1.1 🎉

The release is available on:

• npm package (@latest dist-tag)
• GitHub release

Your semantic-release bot 📦🚀

[basarbk]

I believe this is not a correct approach to fix this. Rerender does not necessearily require component to be destroyed.
Lets say there is a UserPage and it is visible for paths like /user/:id . A sample routing would be like this (either with svelte-routing or svelte-navigator). We can pass the id as param

<Route path="/user/:id" let:params>
   <UserPage id={params.id} />
</Route>

When we navigate from /user/1 to /user/2, UserPage component is not destroyed. Only the prop, id is now has the value, 2.

But in test, since rerender is destroying and mounting the component, even an incorrect implementation like this one is passing the test. So it ends up with false positive result. But in reality, the same scenario fails.

I have this repo shows the issue.