trailingSlash + unexistent page should return 404 instead of 308 + 404

Bug report

Describe the bug

When a route does not exist and does not have the trailingSlash, for example:

localhost:3000/whatever

First it’s redirecting with 308 to:

localhost:3000/whatever/

And then is displaying the 404 page with the status 404.

To Reproduce

1. Add trailingSlash: true on the next.js config
2. Curl an unexisting URL without trailingSlash

Expected behavior

Would be better to directly display the 404 page avoiding the 308 redirecting for these cases.

Screenshots

System information

• OS: macOS
• Version of Next.js: 9.5.2
• Version of Node.js: 14.8.0

[jordic]

I can confirm what @aralroca is saying, when you manage a large set of urls, and you want to improve the performance of googlebot indexing them, that’s an small improvement, because serving a 308 triggers a new crawl actoin, to finally fetch a 404. (It’s better, in terms of performance to just serve the 404).

[aralroca]

I thought that for SEO as fewer redirects possible better, and showing the page 404 directly made sense in this case. I have reported it because we had implemented it with a custom server before this feature landed in the new version of Next. But it is likely that I am wrong, so if it is done so because it is considered better, ok 👍