Make dev environment match production environment more closely

Describe the problem

I'm not sure if this is a bug so much as a discussion I'd like to have. One basic premise of sveltekit is that we have a local dev experience that matches closely to the production experience.

I find that one area where this promise is broken is when you try to render-on-demand rather than prerender, because it is very common for serverless environments (netlify, vercel et al) to separately bundle and run the serverless function. So, if I have a page that is only rendered on demand, its very easy for me to code a file read that works in dev, but then breaks when done in prod:

import { resolve } from 'path';
import { promises as fs } from 'fs';

const x = await fs.readFile(resolve('./podcasts.yml'), 'utf8')

this code works fine in dev, but then deploy it and...

{"errorType":"Runtime.UnhandledPromiseRejection","errorMessage":"Error: ENOENT: no such file or directory, open '/var/task/podcasts.yml'","trace":["Runtime.UnhandledPromiseRejection: Error: ENOENT: no such file or directory, open '/var/task/podcasts.yml'"," at process.<anonymous> (/var/runtime/index.js:35:15)"," at process.emit (events.js:400:28)"," at processPromiseRejections (internal/process/promises.js:245:33)"," at processTicksAndRejections (internal/process/task_queues.js:96:32)"]}

Describe the proposed solution

i think we should try to shift this problem left - if the page is serverless, actually compile the function and make it properly isolated as it would be in prod

Alternatives considered

do nothing, let people fumble around with this new serverless rendering paradigm :(

for what its worth i'm a veteran Netlify user, spent multiple hours trying to figure out how to get around this and still havent got anything i'm really happy with (apart from brute force copying the file postbuild into the built folder, which really feels super janky and not great)

Importance

would make my life easier

Additional Information

No response

Start by reproducing the difference between local rendering and a separately bundled serverless deployment using the podcasts.yml file-read example. Investigate how serverless pages are built and isolated, then define done as development behavior exposing the same missing-file failures or asset handling as production.