Adapter "cannot find module" as of upgrade to recent version

[wallw-teal]

Describe the bug

I have an error that has cropped up in @sveltejs/[email protected] and @sveltejs/[email protected]. I have a component that uses an OpenLayers map and I get the following from the adapter portion of the build:

Run npm run preview to preview your production build locally.

Using @sveltejs/adapter-node
Error [ERR_MODULE_NOT_FOUND]: Cannot find module '<monorepo_project>/node_modules/ol/Feature' imported from <monorepo_project>/packages/app/.svelte-kit/output/server/entries/pages/search.svelte.js
Did you mean to import ol/Feature.js?
    at new NodeError (node:internal/errors:371:5)
    at finalizeResolution (node:internal/modules/esm/resolve:416:11)
    at moduleResolve (node:internal/modules/esm/resolve:932:10)
    at defaultResolve (node:internal/modules/esm/resolve:1044:11)
    at ESMLoader.resolve (node:internal/modules/esm/loader:422:30)
    at ESMLoader.getModuleJob (node:internal/modules/esm/loader:222:40)
    at ModuleWrap.<anonymous> (node:internal/modules/esm/module_job:76:40)
    at link (node:internal/modules/esm/module_job:75:36)

This worked as of 193/55, I first saw the error in 202/56, and still see it in 215/60. I do not think it is specific to that import, since if I remove it, it just complains about another file from OpenLayers instead. <monorepo_project>/node_modules/ol/Feature.js exists, so I do not know why it is having trouble finding that.

I should note that npm run dev works fine and does not complain about anything

Reproduction

See minimal reproduction at https://github.com./wallw-bits/svelte-kit-ol-issue-repro and npm i followed by npm run build.

Logs

No response

System Info

System:
    OS: Linux 5.11 Ubuntu 20.04.3 LTS (Focal Fossa)
    CPU: (16) x64 Intel(R) Core(TM) i9-9980HK CPU @ 2.40GHz
    Memory: 6.19 GB / 31.11 GB
    Container: Yes
    Shell: 5.0.17 - /bin/bash
  Binaries:
    Node: 16.13.0 - ~/.nvm/versions/node/v16.13.0/bin/node
    Yarn: 1.22.17 - ~/.nvm/versions/node/v16.13.0/bin/yarn
    npm: 7.24.2 - ~/workspace/saffire/ui/node_modules/.bin/npm
  Browsers:
    Chrome: 96.0.4664.110
    Firefox: 95.0.1
  npmPackages:
    @sveltejs/adapter-node: ^1.0.0-next.60 => 1.0.0-next.60 
    @sveltejs/kit: ^1.0.0-next.215 => 1.0.0-next.215 
    svelte: ^3.44.3 => 3.44.3

Severity

blocking an upgrade

Additional Information

No response

[wallw-teal]

I ran a bisection and it appears that this first shows up with the upgrade to Vite 2.7 in 09e453f

Edit: Tried running that reproduction with the latest Vite via npm i -D vite and that did not help.

[wallw-teal]

It looks like I can work around this by doing dynamic imports inside of onMount:

<script lang="ts">
  import { onMount } from "svelte";

  let feature;

  onMount(async () => {
    const Feature = (await import("ol/Feature")).default;
    feature = new Feature({ value: 42 });
  });
</script>

{#if feature}
  <p>It worked!</p>
{/if}

That's still really ugly though. Why does the tree shaking not know that the Feature import is unused in SSR?

[wallw-teal]

NODE_OPTIONS='--es-module-specifier-resolution=node' npm run build is a cleaner workaround

Edit: To sum up, it would be helpful if svelte-kit's Vite config (or maybe Vite doesn't have the option, not sure) for the server output used file extensions, per the default value of explicit for --es-module-specifier-resolution.

The bit about that import not really being needed at all on the server since it isn't used until onMount might be a separate tree-shaking issue.

[benmccann]

This code is invalid:

import Feature from "ol/Feature";

Change it to:

import Feature from "ol/Feature.js";

If you'd like to leave off the extension then the ol package would need to define exports in its package.json

[benmccann]

It is curious that the non-spec compliant code worked in an older version of Vite. If you'd like that support to be added back, I'd recommend filing an issue there.

[wallw-teal]

Yup, I understand why that is not valid per the ES spec. However, why doesn't the rest of the tooling have an issue with it?

[benmccann]

No idea. The Vite folks might know better

[bluwy]

Similar as vitejs/vite#6193. But this is an issue within Openlayers itself, not Vite, as the error is coming from node. Since ol is using type: module, they should use exports to support the ol/Feature syntax, otherwise ol/Feature.js is required. I'm not sure how it used to work pre Vite 2.7 though, perhaps there were changes that surfaced the issue within Openlayers.