Fallthrough routes (2 routes with slugs on same level) Regression issue .137

[zwergius]

Describe the bug

I cannot make a route fallthough when in SSR, this works as expected when client is navigating

This also affects when I export with static-adapter as all these routes return 500

Reproduction

This issue only appears in SSR mode, I reproduce by going to the route in question and refreshing (F5)

I have 2 routes:

src/routes/[legal]/index.svelte
src/routes/[page]/index.svelte

I manually check in my load function inside src/routes/[legal]/index.svelte
if (!validRoute) return

But this never reaches the load function in src/routes/[page]/index.svelte I see a 500 Internal server error in my console and the page shows the following message:

Bad request in load function: “failed to fetch undefined”

Logs

No response

System Info

System:
    OS: macOS 11.5.1
    CPU: (12) x64 Intel(R) Core(TM) i7-8850H CPU @ 2.60GHz
    Memory: 4.60 GB / 32.00 GB
    Shell: 5.8 - /bin/zsh
  Binaries:
    Node: 16.5.0 - ~/.n/bin/node
    Yarn: 1.22.10 - ~/.n/bin/yarn
    npm: 7.19.1 - ~/.n/bin/npm
  Browsers:
    Brave Browser: 91.1.26.77
    Chrome: 92.0.4515.107
    Firefox: 89.0.2
    Safari: 14.1.2
    Safari Technology Preview: 15.0
  npmPackages:
    @sveltejs/adapter-static: ^1.0.0-next.7 => 1.0.0-next.13 
    @sveltejs/kit: ^1.0.0-next.109 => 1.0.0-next.138 
    svelte: ^3.40.1 => 3.41.0 
    vite: ^2.1.0 => 2.4.4

Severity

blocking an upgrade

Additional Information

No response

[dominikg]

Relevant discord discussion: https://discord.com/channels/457912077277855764/819723698415599626/870554215091683339

From Rainlife's comment it looks like this worked in .136 and broke with .137

[manvankaliber]

all my route-name/index.svelte routes are broken now too. route-name.svelte is fine though. It simply returns no handler to me. I think it worked fine in version .136

[benmccann]

Hmm. 137 enabled strict TypeScript checking: https://github.com/sveltejs/kit/blob/master/packages/kit/CHANGELOG.md#100-next137

It's a pretty big diff, so not easy to narrow down from the diff what might have changed

Can either of you provide a repository that reproduces this?

[JulienPradet]

Hi @benmccann,

Here is a reproduction repo that contains two issues I've noticed: https://github.com/JulienPradet/sveltekit-2041

• index.svelte + index.js conflict : previously, if an endpoint had no get method, it was using the index.svelte file as a fallback. http://localhost:3000/ displays no handler in the newer versions.
• between [legal].svelte and [page].svelte, if the load function of the [legal].svelte didn't return anything, it should fallback to the [page].svelte (so in the case of the repository, http://localhost:3000/valid should display "Legal" but http://localhost:3000/invalid should display "Page"

I couldn't reproduce @UltraCakeBakery's issue though but I guess it's close to the endpoint issue.

[benmccann]

We have tests for fallthrough, but it turns out they're not running 🤷 #2069

[benmccann]

Tests are now running and failing. Now they need to be fixed

[harvey-k]

@benmccann Not sure if this is helpful, but the more complicated test seems to have broken in the commit below:
bce1d76#diff-f8956b07fb67847bf592e4b63a47d10053d7bdd1b484a4897eb385aab567dd2d

The specific file linked is part of what you changed in #2072

Your efforts are appreciated!