Compiled js map can be a null

[MartkCz]

Describe the bug

Cannot import plugin if compilerOptions -> enableSourcemap is set to false.

Error: [plugin: vite-plugin-svelte:optimize-svelte] Cannot read properties of null (reading 'toUrl') at compileSvelte

The problem line of plugin: import RenderTemplate from './RenderTemplate.svelte';"

Full code of problem file:

import RenderTemplate from './RenderTemplate.svelte';

export { RenderTemplate };
export * from './Template.js';

Because of https://github.com/sveltejs/vite-plugin-svelte/blob/main/packages/vite-plugin-svelte/src/utils/esbuild.js#L109 compiled.js.map is null

If compilerOptions -> enableSourcemap is true, everything works fine.

Reproduction URL

https://stackblitz.com/edit/vitejs-vite-9dzyn1?file=vite.config.js

Reproduction

No response

Logs

No response

System Info

System:
    OS: Linux 5.15 Manjaro Linux
    CPU: (12) x64 AMD Ryzen 5 5600G with Radeon Graphics
    Memory: 16.78 GB / 30.70 GB
    Container: Yes
    Shell: 5.9 - /bin/zsh
  Binaries:
    Node: 20.5.0 - /usr/bin/node
    npm: 9.8.1 - /usr/bin/npm
  npmPackages:
    @sveltejs/vite-plugin-svelte: ^2.4.5 => 2.4.5 
    svelte: ^4.1.2 => 4.2.0 
    vite: ^4.4.9 => 4.4.9

[dominikg]

The optimizer is only used during dev and having sourcemaps is better in dev. You can use the function arg of defineConfig to disable sourcemaps only on build.

import { defineConfig } from 'vite';
import { svelte } from '@sveltejs/vite-plugin-svelte';

// https://vitejs.dev/config/
export default defineConfig(({ command }) => ({
  plugins: [
    svelte({
      compilerOptions: {
        enableSourcemap: command !== 'build',
      },
    }),
  ],
}));

That being said we should either be able to handle missing sourcemaps on dev or force it to true. @bluwy what do you think?

[bluwy]

I think we could handle missing sourcemaps in dev, rather than forcing it to true 🤔 We do force some options but maybe we should do it sparingly and only when needed, in this case, it's probably fine if there's no sourcemaps if that's what the user wanted.

[MartkCz]

I don't know why I disabled sourcemaps, but when I installed a 3rd party package, this error appeared and it was hard to detect the problem. Imho a better error message would have sufficed.

[paulovieira]

I was also caught by this problem today when trying to extract a component from a sveltekit app to a separate package. I actually prefer to have compilerOptions.enableSourcemap as false because it's easier to understand what svelte is doing behind the scenes.

I tried to fix the problem in different ways, and an alternative that seems to work is to add this to svelte.config.js:

const config = {
    ...
    vitePlugin: { prebundleSvelteLibraries: false }
}

This way I can import svelte components from external packages and still have source maps disabled.

Either way, it would be great if this could be fixed in src/utils/esbuild.js.

Thanks.