Cannot import yjs using SvelteKit and adapter-static: SyntaxError: Cannot use import statement outside a module

[nokola]

Describe the bug

Starting with a simple electron + web template for SvelteKit for experimentation. I tried adding yjs to it, but getting the error in Logs.
Works just fine in my non-sveltekit svelte app.

Reproduction

1. Clone https://github.com/nokola/testSvelteKit
2. Run:

yarn
yarn build

Expected: all OK
Actual: build error:

> Using @sveltejs/adapter-static
(node:16116) Warning: To load an ES module, set "type": "module" in the package.json or use the .mjs extension.
(Use `node --trace-warnings ...` to show where the warning was created)
import * as Y from 'yjs' // eslint-disable-line
^^^^^^

SyntaxError: Cannot use import statement outside a module
    at wrapSafe (internal/modules/cjs/loader.js:979:16)
    at Module._compile (internal/modules/cjs/loader.js:1027:27)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1092:10)
    at Module.load (internal/modules/cjs/loader.js:928:32)
    at Function.Module._load (internal/modules/cjs/loader.js:769:14)
    at ModuleWrap.<anonymous> (internal/modules/esm/translators.js:199:29)
    at ModuleJob.run (internal/modules/esm/module_job.js:152:23)
    at async Loader.import (internal/modules/esm/loader.js:166:24)
    at async Object.load_component (file:///D:/Repos/Local/my-app/.svelte-kit/output/server/chunks/app-024aa19a.js:1503:13)
    at async Promise.all (index 1)
(node:16116) UnhandledPromiseRejectionWarning: SyntaxError: Cannot use import statement outside a module
(node:16116) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled 
promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 1)
(node:16116) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
> 500 /
Error: 500 /
    at file:///D:/Repos/Local/my-app/node_modules/@sveltejs/kit/dist/chunks/index4.js:86:11
    at visit (file:///D:/Repos/Local/my-app/node_modules/@sveltejs/kit/dist/chunks/index4.js:222:5)
    at async prerender (file:///D:/Repos/Local/my-app/node_modules/@sveltejs/kit/dist/chunks/index4.js:303:6)
    at async Object.prerender (file:///D:/Repos/Local/my-app/node_modules/@sveltejs/kit/dist/chunks/index4.js:368:4)
    at async adapt (file:///D:/Repos/Local/my-app/node_modules/@sveltejs/adapter-static/index.js:13:4)
    at async adapt (file:///D:/Repos/Local/my-app/node_modules/@sveltejs/kit/dist/chunks/index4.js:393:2)
    at async file:///D:/Repos/Local/my-app/node_modules/@sveltejs/kit/dist/cli.js:896:5

Note: failure happens if yjs is used in any way, see index.svelte:

<script>
    import * as S from "y-websocket"
    S.test();
</script>

Logs

PS D:\Repos\GitHub\testSvelteKit> yarn build
yarn run v1.22.17
$ svelte-kit build
vite v2.6.14 building for production...
transforming (44) node_modules\lib0\conditions.js'test' is not exported by 'node_modules\y-websocket\src\y-websocket.js'
✓ 58 modules transformed.
.svelte-kit/output/client/_app/manifest.json                               2.04 KiB
.svelte-kit/output/client/_app/pages/__layout.svelte-25daf92b.js           1.54 KiB / gzip: 0.78 KiB
.svelte-kit/output/client/_app/error.svelte-6be86a66.js                    1.56 KiB / gzip: 0.75 KiB
.svelte-kit/output/client/_app/pages/index.svelte-e288b0c2.js              1.83 KiB / gzip: 0.94 KiB
.svelte-kit/output/client/_app/pages/page1.svelte-6e46b093.js              1.44 KiB / gzip: 0.72 KiB
.svelte-kit/output/client/_app/pages/page2.svelte-508cb7a1.js              1.48 KiB / gzip: 0.73 KiB
.svelte-kit/output/client/_app/pages/page3.svelte-06e9be0e.js              1.44 KiB / gzip: 0.72 KiB
.svelte-kit/output/client/_app/assets/start-61d1577b.css                   0.16 KiB / gzip: 0.15 KiB
.svelte-kit/output/client/_app/assets/pages/__layout.svelte-118da309.css   0.68 KiB / gzip: 0.40 KiB
.svelte-kit/output/client/_app/start-0f28ad9d.js                           18.94 KiB / gzip: 6.93 KiB
.svelte-kit/output/client/_app/assets/pages/index.svelte-1a7d65f4.css      0.32 KiB / gzip: 0.19 KiB
.svelte-kit/output/client/_app/chunks/vendor-d6b0b8d4.js                   7.32 KiB / gzip: 2.99 KiB
vite v2.6.14 building SSR bundle for production...
✓ 21 modules transformed.
.svelte-kit/output/server/app.js                        0.07 KiB
.svelte-kit/output/server/chunks/app-02114f6d.js        50.04 KiB
.svelte-kit/output/server/chunks/__layout-53c16722.js   0.60 KiB
.svelte-kit/output/server/chunks/error-b29df138.js      0.71 KiB
.svelte-kit/output/server/chunks/index-fb13d36b.js      1.30 KiB
.svelte-kit/output/server/chunks/page1-649e60b9.js      0.60 KiB
.svelte-kit/output/server/chunks/page2-575d970b.js      0.63 KiB
.svelte-kit/output/server/chunks/page3-422e4654.js      0.60 KiB

Run npm run preview to preview your production build locally.

> Using @sveltejs/adapter-static
(node:8212) Warning: To load an ES module, set "type": "module" in the package.json or use the .mjs extension.
(Use `node --trace-warnings ...` to show where the warning was created)
D:\Repos\GitHub\testSvelteKit\node_modules\y-websocket\src\y-websocket.js:11
import * as Y from 'yjs' // eslint-disable-line
^^^^^^

SyntaxError: Cannot use import statement outside a module
    at wrapSafe (internal/modules/cjs/loader.js:979:16)
    at Module._compile (internal/modules/cjs/loader.js:1027:27)
    at Object.Module._extensions..js (internal/modules/cjs/loader.js:1092:10)
    at Module.load (internal/modules/cjs/loader.js:928:32)
    at Function.Module._load (internal/modules/cjs/loader.js:769:14)
    at ModuleWrap.<anonymous> (internal/modules/esm/translators.js:199:29)
    at ModuleJob.run (internal/modules/esm/module_job.js:152:23)
    at async Loader.import (internal/modules/esm/loader.js:166:24)
    at async Object.load_component (file:///D:/Repos/GitHub/testSvelteKit/.svelte-kit/output/server/chunks/app-02114f6d.js:1527:13)
    at async Promise.all (index 1)
(node:8212) UnhandledPromiseRejectionWarning: SyntaxError: Cannot use import statement outside a module
(node:8212) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). To terminate the node process on unhandled promise rejection, use the CLI flag `--unhandled-rejections=strict` (see https://nodejs.org/api/cli.html#cli_unhandled_rejections_mode). (rejection id: 2)
(node:8212) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future, promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
> 500 /
Error: 500 /
    at file:///D:/Repos/GitHub/testSvelteKit/node_modules/@sveltejs/kit/dist/chunks/index4.js:86:11
    at visit (file:///D:/Repos/GitHub/testSvelteKit/node_modules/@sveltejs/kit/dist/chunks/index4.js:222:5)
    at async prerender (file:///D:/Repos/GitHub/testSvelteKit/node_modules/@sveltejs/kit/dist/chunks/index4.js:303:6)
    at async Object.prerender (file:///D:/Repos/GitHub/testSvelteKit/node_modules/@sveltejs/kit/dist/chunks/index4.js:368:4)
    at async adapt (file:///D:/Repos/GitHub/testSvelteKit/node_modules/@sveltejs/adapter-static/index.js:13:4)
    at async adapt (file:///D:/Repos/GitHub/testSvelteKit/node_modules/@sveltejs/kit/dist/chunks/index4.js:393:2)
    at async file:///D:/Repos/GitHub/testSvelteKit/node_modules/@sveltejs/kit/dist/cli.js:896:5
error Command failed with exit code 1.
info Visit https://yarnpkg.com/en/docs/cli/run for documentation about this command.
PS D:\Repos\GitHub\testSvelteKit>

System Info

System:
    OS: Windows 10 10.0.19043
    CPU: (16) x64 AMD Ryzen 7 3700X 8-Core Processor
    Memory: 32.57 GB / 47.92 GB
  Binaries:
    Node: 14.16.0 - C:\Program Files\nodejs\node.EXE
    Yarn: 1.22.17 - ~\AppData\Roaming\npm\yarn.CMD
    npm: 6.14.11 - C:\Program Files\nodejs\npm.CMD
  Browsers:
    Edge: Spartan (44.19041.1266.0), Chromium (96.0.1054.29)     
    Internet Explorer: 11.0.19041.1202
  npmPackages:
    @sveltejs/adapter-node: next => 1.0.0-next.55 
    @sveltejs/adapter-static: next => 1.0.0-next.21 
    @sveltejs/kit: next => 1.0.0-next.201 
    svelte: ^3.29.0 => 3.44.2 
    vite: ^2.1.0 => 2.6.14

Severity

blocking all usage of SvelteKit

Additional Information

No response

[benmccann]

I see another user ran into issues with this library: #2639

This appears to be an issue in the library itself: yjs/y-websocket#72

[nokola]

Thanks for the investigation! Very useful!