What causes "Sourcemap for [...] points to missing source files"?

[jtlapp]

I've spent the day trying to convert my sveltekit repo to a monorepo. After copying my former repo to a package, yarn run dev -- gives me the following errors:

Sourcemap for "/Users/joe/repos/cavesite-new/packages/frontend/src/common/VariableFlash.svelte" points to missing source files
Sourcemap for "/Users/joe/repos/cavesite-new/packages/frontend/src/components/HeaderBar.svelte" points to missing source files
Sourcemap for "/Users/joe/repos/cavesite-new/packages/frontend/src/common/Notice.svelte" points to missing source files
Sourcemap for "/Users/joe/repos/cavesite-new/packages/frontend/src/dialogs/LoginDialog.svelte" points to missing source files
Sourcemap for "/Users/joe/repos/cavesite-new/packages/frontend/src/components/RouteTab.svelte" points to missing source files

However, if I place "mapRoot": "whatever" into tsconfig.json, then I get vastly more such errors, so it's clear that it's happy with many source maps despite the above errors.

I'm using adapter-node, and here's my tsconfig.json:

{
    "extends": "./.svelte-kit/tsconfig.json",
    "compilerOptions": {
        "strict": true,
        "pretty": true,
        "noUnusedLocals": true,
        "noUnusedParameters": true,
        "noImplicitReturns": true,
        "noFallthroughCasesInSwitch": true,
        "noEmitOnError": true
    }
}

What might cause this problem?

[jtlapp]

I don't get these errors in my original repo. I installed svelte-kit from scratch into the new monorepo package and selectively copied files from the old repo in, but I still get the problem.

So either copying svelte config files to a new directory can break things, or it's copying to a pnpm package directory that breaks things.

[jtlapp]

I've tried these two config files and everything in between:

import adapter from '@sveltejs/adapter-node';
import preprocess from 'svelte-preprocess';

/** @type {import('@sveltejs/kit').Config} */
const config = {
	preprocess: preprocess(),
	kit: {
		adapter: adapter()
	}
};

export default config;

import adapter from '@sveltejs/adapter-node';
import preprocess from 'svelte-preprocess';

/** @type {import('@sveltejs/kit').Config} */
const config = {
	tsconfigFile: "./tsconfig.json",
	compilerOptions: {
		enableSourcemap: true,
	},
	preprocess: preprocess({
		sourceMap: true
	}),
	kit: {
		adapter: adapter()
	}
};

export default config;

[possan]

I had similar problems with the build step finding files within the node_modules folder, downgrading vite seems to have solved it for me, i currently have "vite": "2.7.1" in my package.json, not sure if it helps.

[jtlapp]

Thank you @possan. Googling around also offered that explanation, but vite is a svelte-kit dependency, so I'm not sure how to downgrade it except by downgrading svelte-kit.

[possan]

Ah yes, we are not yet on the latest sveltekit and those newer versions might require a more recent vite, i haven't tried that yet.

[possan]

Tried it, and yes, 💥

[jtlapp]

Wait. You tried to upgrade sveltekit and now you're getting these errors? I was going to try downgrading to see if that helped.

[bfanger]

Some (maybe all) are related to postcss generating wrong paths into sourcemap because svelte-preprocess is not passing a to parameter.
Fixed in sveltejs/svelte-preprocess#500

[jtlapp]

That could be. But in my case, the code was not producing these errors until I split it into separate packages of a monorepo.

[bfanger]

Edit both packages/frontend/node_modules/svelte-preprocess/dist/transformers/globalStyle.js & postcss.js

and replace:

from: filename,

with

from: filename, 
to: filename,

In my tests with a monorepo and the example SvelteKit app this fixed the issue.

[benmccann]

svelte-preprocess 4.10.6 has been released. Please upgrade and let us know if it works. If it does not then please provide a repository that reproduces the issue

[jtlapp]

Thanks for producing a fix! Unfortunately, I didn't keep my very broken pnpm monorepo, so I can't test this. But it sounds like @possan also faced this issue attempting to upgrade, so maybe he can check it out.

[djavorek]

@benmccann Thank you. I have faced this issues, looks OK now with: "svelte-preprocess": "4.10.6",