Trailing slash automatically removed when using basePath and url has query params

What version of Next.js are you using?

11.0.1

What version of Node.js are you using?

12.16.1

What browser are you using?

Chrome 92.0.4515.131

What operating system are you using?

macOS Big Sur

How are you deploying your application?

next build && next export, static files on AWS S3

Describe the Bug

When URL has query params, e. g. mydomain.com/basePath/?params=1 it automatically removes slash and comes to mydomain.com/basePath?params=1

This is affecting our analytics.

It happens only when basePath is configured. We have tested and slash persists without basePath and without query params

Expected Behavior

We would like all URL’s to end with a /, even it has query params. Because it affect to analytics and for internal links.

To Reproduce

next.config.js:

{
  ...
  basePath: '/base-path',
  trailingSlash: true,
  ...
  }

And write to URL any query params after slash and hit enter For example go to domain.com/base-path/?query=true it comes to domain.com/base-path?query=true

[LetItRock]

hi @IhorVoit!

from what do I see in the code the router is not respecting the trailingSlash config in the function addPathPrefix when the path is like /?asd=asd, then the / is stripped out from path without checking the trailingSlash, and then is concatenated with the basePath, so in result, it ends like /base-path?asd=asd instead of /base-path/?asd=asd. Also, it only happens for the root path /, the dynamic pages, and others like /about are working fine.

@ijjk fyi

[IhorVoit]

Hi, @ijjk! Thanks a lot, problem solved! Can I use this version of package in production or should I wait for next stable version?