Importing TS files from component is not working when script tag spans multiple lines

[fehnomenal]

Describe the bug

If the <script lang="ts"> has a long generics attribute that causes prettier to break it into multiple lines, imports with a .js extension that should resolve to a TS file are no longer working.

<script
  lang="ts"
  generics="SomethingLongToTriggerReformat extends Record<string, unknown>, MoreStrings extends keyof SomethingLongToTriggerReformat"
>
  import { test } from './lib/test.js';
</script>

{test}

If you change the import to './lib/test.ts' or './lib/test' it works again.
If you add a space after <script it also works again.

Reproduction

Repo: https://github.com/fehnomenal/svelte-ts-import

This is the vite@latest svelte template stripped of all unneeded stuff.

The second commit (fehnomenal/svelte-ts-import@91e042f) gives the diff as an example.

Logs

❯ pnpm build

> [email protected] build /tmp/svelte-ts-import
> vite build

vite v5.4.11 building for production...
✓ 15 modules transformed.
x Build failed in 70ms
error during build:
Could not resolve "./lib/test.js" from "src/App.svelte"
file: /tmp/svelte-ts-import/src/App.svelte
    at getRollupError (file:///tmp/svelte-ts-import/node_modules/.pnpm/[email protected]/node_modules/rollup/dist/es/shared/parseAst.js:396:41)
    at error (file:///tmp/svelte-ts-import/node_modules/.pnpm/[email protected]/node_modules/rollup/dist/es/shared/parseAst.js:392:42)
    at ModuleLoader.handleInvalidResolvedId (file:///tmp/svelte-ts-import/node_modules/.pnpm/[email protected]/node_modules/rollup/dist/es/shared/node-entry.js:20085:24)
    at file:///tmp/svelte-ts-import/node_modules/.pnpm/[email protected]/node_modules/rollup/dist/es/shared/node-entry.js:20045:26
 ELIFECYCLE  Command failed with exit code 1.

System Info

System:
    OS: Linux 6.6 cpe:/o:nixos:nixos:24.11 24.11 (Vicuna)
    CPU: (16) x64 AMD Ryzen 7 7840HS w/ Radeon 780M Graphics
    Memory: 9.77 GB / 60.64 GB
    Container: Yes
    Shell: 0.99.1 - /run/current-system/sw/bin/nu
  Binaries:
    Node: 23.1.0 - /etc/profiles/per-user/andi/bin/node
    npm: 10.9.0 - /etc/profiles/per-user/andi/bin/npm
    pnpm: 9.14.1 - /etc/profiles/per-user/andi/bin/pnpm
    bun: 1.1.31 - /etc/profiles/per-user/andi/bin/bun
  Browsers:
    Chromium: 130.0.6723.91
  npmPackages:
    svelte: 5.2.7 => 5.2.7

Severity

annoyance

[fehnomenal]

OK, I found the problem is caused by vite-plugin-svelte. It uses a similar regex as the compiler to extract the script tag's language. But it has this as an edge case.
Fix:

 const scriptLangRE =
-	/<!--[^]*?-->|<script (?:[^>]*|(?:[^=>'"/]+=(?:"[^"]*"|'[^']*'|[^>\s]+)\s+)*)lang=["']?([^"' >]+)["']?[^>]*>/g;
+	/<!--[^]*?-->|<script\s+(?:[^>]*|(?:[^=>'"/]+=(?:"[^"]*"|'[^']*'|[^>\s]+)\s+)*)lang=["']?([^"' >]+)["']?[^>]*>/g;

[fehnomenal]

I submitted a PR at the repo: sveltejs/vite-plugin-svelte#1028

[dummdidumm]

Closing since this was fixed in v-p-s