svelte-kit build swallows typescript errors

Describe the bug Errors in .ts files are silently ignored when running svelte-kit build.

Logs N/A

To Reproduce

1. Enable some feature in tsconfig.json, such as strictNullChecks or noUnusedLocals, then write some code that breaks that rule. For example, setting noUnusedLocals: true then writing let unusedVar = 42;.
2. Run svelte-kit build

Expected behavior I expect that svelte-kit build would fail (exit != 0) and give a helpful error message. Instead it just silently succeeds, even though compiling the exact same code with tsc correctly errors.

Stacktraces N/A

Information about your SvelteKit Installation:

N/A

Severity Very annoying, means that I can’t rely on the build process to catch errors so I have to spend extra time checking for them manually and also worry about an avoidable bug slipping through the cracks.

Additional context N/A

[thislooksfun]

Sure it’s more explicit, but there’s still a reason why tooling like tsc has it built in. Besides, that still doesn’t address having type checking as part of svelte-kit dev which would be insanely useful for detecting errors as we go, rather than having to manually check afterwards.

[dummdidumm]

svelte-kit dev uses Vite under the hood, which does not do any type checking. So if it was “built-in”, it would again mean that svelte-check --watch is called, which I’d rather have explicit in my package.json. My development workflow for example relies on IDE checks during dev and then svelte-check prior to the build. It works for other CLIs like Angular or Vue because they use webpack, where they can integrate the typechecking into the process.