Rollup dev server dev traces link to __sapper__ folder instead of typescript source

[ubershmekel]

Describe the bug While using the dev server, I would like server crashes to link to the typescript source files in which they occur. Instead the crashes print out the JavaScript generated file paths.

Logs TypeError: Cannot read property 'players' of undefined at sendUsersList (D:\1stuff\dev\2021\sapper-template-rollup-master_sapper_\dev\server\server.js:5803:28) at Socket. (D:\1stuff\dev\2021\sapper-template-rollup-master_sapper_\dev\server\server.js:5856:9) at Socket.emit (node:events:376:20) at D:\1stuff\dev\2021\sapper-template-rollup-master\node_modules\socket.io\dist\socket.js:434:28 at processTicksAndRejections (node:internal/process/task_queues:75:11)

Server crashed

Notice the js files and __sapper__ folder, instead of the actual server.ts source file. I've tried to use the advice from here: https://stackoverflow.com/questions/63218218/rollup-is-not-generating-typescript-sourcemap but it didn't seem to work.

To Reproduce Please make sure you've tested with the latest versions of Svelte and Sapper.

"sapper": "^0.28.0",
"svelte": "^3.17.3",

Information about your Sapper Installation:

• The output of npx envinfo --system --npmPackages svelte,sapper,rollup,webpack --binaries --browsers

System: OS: Windows 10 10.0.19041 CPU: (8) x64 Intel(R) Core(TM) i7-4770K CPU @ 3.50GHz Memory: 17.31 GB / 31.94 GB Binaries: Node: 15.4.0 - C:\Program Files\nodejs\node.EXE npm: 7.0.15 - C:\Program Files\nodejs\npm.CMD Browsers: Chrome: 87.0.4280.141 Edge: Spartan (44.19041.423.0), Chromium (88.0.705.56) Internet Explorer: 11.0.19041.1 npmPackages: rollup: ^2.3.4 => 2.38.0 sapper: ^0.28.0 => 0.28.10 svelte: ^3.17.3 => 3.31.2

• Your browser: at build time.

• Your hosting environment: local

• If it is an exported (npm run export) or dynamic application: when running npm run dev

Severity How severe an issue is this bug to you? Is this annoying, blocking some users, blocking an upgrade or blocking your usage of Sapper entirely?

It's a bit annoying, but I can work around it.