getServerSideProps data urls don't respect assetPrefix

Bug report

Describe the bug

I have assetPrefix set because we are hosting multiple applications on the same domain and use a proxy to route paths.

assetPrefix = "reports"

The static asset urls are correct. Such as /reports/_next/static/development/pages/_app.js?ts=1587171521639.

However, the data fetching URLs are NOT including the prefix: /_next/data/development/reports/appointments/2020-03-18/2020-04-17.json.

To Reproduce

• Set assetPrefix to anything
• Create a page with getServerSideProps
• use the router (or Link) to go to that page on the client
• Observe in the network request inspector that the data urls do not include the assetPrefix.

Expected behavior

I would expect the assetPrefix to apply to ALL asset urls that start with _next/

[pueyo5]

Please use the new basePath support instead of assetPrefix in Next.js 9.5.1+ for this use case!

@Timer In our case, this is not possible. The basePath is expecting a subfolder, and we want to use a subdomain. We are using https://cdn.domain.com and for the proposed solution we have to use https://domain.com/cdn.

Can this issue be reopened or do you want me to create a new one?

[daveskybet]

Poking about with the code (i’m no expert in the codebase), here seems to be the culprit:

https://github.com/zeit/next.js/blob/canary/packages/next/next-server/lib/router/router.ts#L94

Which seems to add an experimental basePath if exists, rather than the assetPrefix as I would have expected (as gets added to the preload tags for the json files)

A quick addition of the assetPrefix to this line fixes my problem (with an ssg site using getStaticProps), but i’m questioning whether we’re misunderstanding the expected behaviour (with the basePath addition)?