Make strict mode the default when choosing Typescript

[dummdidumm]

Describe the problem

From a recent conversation I learned that nowadays almost every Typescript starter template of other frameworks (example: the vite templates) and the typescript cli itself default to turning on strict mode. This issue is intended to discuss turning strict mode on for create-svelte, too, and after that I'm happy to open PRs for the vite/rollup template doing the same.

Arguments in favor of strict mode:

• way easier to have it turned on from the start than turning it on later and converting an existing code base
• the TS ecosystem as a whole recommends turning it on by default
• the strict null checks are very nice for catching nullpointer errors early
• if it's off by default, people might be surprised about nullpointers not getting caught because they thought TS should catch these things, too

Arguments against it:

• Potentially steeper learning curve for those new to it

Describe the proposed solution

Turn on strict mode in the starter templates

Alternatives considered

Only turn on a subset of it, for example only the strict null checks option which is arguably the most important one

Importance

would make my life easier

Additional Information

No response

[Conduitry]

This sounds like a good idea to me.

[frederikhors]

Just to laugh for a moment.

In a recent project (still very small, a few dozen files), activating the strict there are 724 errors with svelte-check. Wow!

Anyway I agree to enable it.

[Rich-Harris]

closed via #4633, which adds "strict": true to the user-editable tsconfig that gets generated when you npm init svelte and choose TypeScript or type-checked JS