[Workers] Added workaround for SvelteKit autoconfig types file error

[neelakolkar-cf]

Closes #30693

Summary

Adds a caution to the SvelteKit framework guide. It explains why the first wrangler deploy on an existing SvelteKit project fails with Types file not found at worker-configuration.d.ts, and how to fix it.

Why

When wrangler deploy automatically configures an existing SvelteKit project, it runs sv add sveltekit-adapter=adapter:cloudflare+cfTarget:workers. Since sveltejs/cli#1057, that add-on puts wrangler types --check in front of the build script. Wrangler then runs the build right away, without generating types first. --check fails because worker-configuration.d.ts does not exist yet.

Reproduction with wrangler 4.149.0, sv 1.1.1 and SvelteKit 3:

1. npx sv create app --template minimal --types ts --no-add-ons
2. npx wrangler deploy: setup runs, then the build fails with Types file not found at worker-configuration.d.ts
3. npx wrangler types, then npx wrangler deploy: builds and deploys normally

The proper fix belongs in workers-sdk: autoconfig should run typegen after sv add and before building (packages/autoconfig/src/frameworks/sveltekit.ts).
This caution should be removed once that fix ships.

Documentation checklist

• Is there a changelog entry (guidelines)? Not needed. This is a docs workaround, not a product change.
• The change adheres to the documentation style guide.

[cloudflare-docs-bot]

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[irvinebroque]

what do we need to do to actually fix this?

[neelakolkar-cf]

what do we need to do to actually fix this?

@irvinebroque Thanks for the quick approval! :)))
The real fix it seems is in workers-sdk autoconfig. In runAutoConfig() (packages/autoconfig/src/run.ts), we write wrangler.jsonc and go straight to the build without generating types. For SvelteKit, sv add (since sveltejs/cli#1057) prepends wrangler types --check to build, so the first build fails because worker-configuration.d.ts doesn't exist yet.

Fix: in run.ts, after the config is saved and before runCommand(buildCommand), run wrangler types (cf workers types for the cf target) for TypeScript projects. It needs to go there, not in frameworks/sveltekit.ts in my opinion, because the final config is only written after configure(). That placement also covers any other framework that adds types --check.

Repro- is in the PR description (wrangler 4.149.0, sv 1.1.1). I'll remove this caution once the fix ships.

[irvinebroque]

Want to make a PR there in workers-sdk?