Issue with index html resources paths when using a complex path as route prefix

[jpb06]

Prerequisites

• I have written a descriptive issue title
• I have searched existing issues to ensure the bug has not already been reported

Fastify version

5.0.0

Plugin version

5.1.0

Node.js version

20.18

Operating system

macOS

Operating system version (i.e. 20.04, 11.3, 10)

15.0.1

Description

It's appears #178 is causing an issue when using a complex path in routePrefix, ie:

await this.instance.register(fastifySwaggerUI, {
  routePrefix: '/api/vi/$docs'
});

The resolved path looks like /api/v1/api/v1/$docs/static in that case.

See linked repo for MRE.

Link to code that reproduces the bug

https://github.com/jpb06/fastify-swagger-ui-routeprefix-issue-repro

Expected Behavior

index resources to load properly.

[mcollina]

Thanks for reporting! Would you like to send a Pull Request to address this issue? Remember to add unit tests.

[jpb06]

Hello.

I spent some time yesterday trying to solve the issue while retaining the behavior wanted by @DavidTanner. Sadly I'm needed elsewhere so I won't have much time to investigate further.

[semy]

Please can you fix that? Have the same problem:
Instead of
const prefix = hasTrailingSlash ? .${opts.staticPrefix}:${hasLeadingSlash ? '.' : ''}${opts.prefix}${opts.staticPrefix}``

should be something like that...
const prefix = hasTrailingSlash ? .${opts.staticPrefix}:${hasLeadingSlash ? '' : '/'}${opts.prefix}${opts.staticPrefix}``

Sorry, but the code is pretty ambiguous anyway, I would generally go over it...

[ronielli]

How do I solve this problem, I still can't?

[NoisyFlowers]

I'm seeing the same problem.

Specifying

routePrefix: "/api/v1/help

and hitting localhost:5000/api/v1/help with browser yields a blank page.

Inspecting the network activity, the initial GET on http://localhost:5000/api/v1/help works, but the ensuing resource GETs all receive 404s because their paths look like this

/api/v1/api/v1/help/static/swagger-ui-bundle.js

Interestingly, adding a trailing "/" (e.g. localhost:5000/api/v1/help/) fixes the problem.

[DavidTanner]

Correct me if I'm wrong, but it kind of seems like this is a bad setup of the server. Can someone please post a test example? I'm going to try recreating in the project as well.

My first thought is that the fastify instance is already using that route prefix, and then you are specifying it again in the swagger config. Again, that is my first thought and I could totally be wrong.

[DavidTanner]

I figured out the issue, and will create a PR to fix. I need to add a new parameter to specify a prefix that only affects the index.html file.

[ronielli]

Good morning, everyone. Do you have an estimated time to approve this pull request?