Fix missing nuxt types

[sarayourfriend]

Description

In the Vue SFC typescript PR #1163 I added the types compiler option to our tsconfig and this removed some critical nuxt types from global scope. Adding them back also revealed that I'd accidentally duplicated the work that the Nuxt vue-i18n module does to make the types work so I was able to remove some code as well.

I also added an ESLint rule to prevent accidentally destructuring the i18n object as it will result in a failure if you do and try to call one of the methods destructured due to the dependency on this in the method.

Testing Instructions

Go to use-i18n.ts and call the function, make sure it has the correct types when you inspect the type information in your editor (try to use some of the properties like .t for example). This tests the removal of the code in the nuxt__types/index.d.ts module and also tests that the types from the module are being added.

Checklist

• My pull request has a descriptive title (not a vague title like Update index.md).
• My pull request targets the default branch of the repository (main) or a parent feature branch.
• My commit messages follow best practices.
• My code follows the established code style of the repository.
• [N/A] I added or updated tests for the changes I made (if applicable).
• I added or updated documentation (if applicable).
• I tried running the project locally and verified that there are no visible errors.

Developer Certificate of Origin

Developer Certificate of Origin

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[krysal]

This looks curious to me 😯 Is p is { href: string } the returning type or an extension of the params type?

[sarayourfriend]

It's a type assertion: https://www.typescriptlang.org/docs/handbook/advanced-types.html#type-guards-and-type-assertions

Basically TypeScript will see this and know that any code that comes after a call to this function that uses it as a condition, that the passed in valid is { href: string } (notably here without the ? on the property making it optional).

// Out here `props.href` is `undefined | string` because `href` is an optional prop

if (checkHref(props)) {
  // in here `props.href` is no long optional, it's "proven" to be an actual string and not undefined by `checkHref`
}

// out here it is optional again because we're outside the conditional

[krysal]

That makes sense for the part of the code using the checkHref function but my doubt is actually with the definition highlighted here 😅

[sarayourfriend]

I see, sorry.

The p is { href: string } is the return type yes. Any return type with the is form is taken to be a predicate and the return value is interpreted as a boolean. It refines the type whatever the caller passes for p at the call site.

With this definition the only part we can encode in the return type is the typeof p.href === 'string' (essentially all that is being said in the return predicate). We could add the second check against the empty string and '#' but TypeScript just throws it away when you actually reference href after the check: https://www.typescriptlang.org/play?#code/C4TwDgpgBACgTgezAZygXigbygCzhAMwH4AuKZYOASwDsBzKAXwChmCBXGgY2CoRqhccELgGsAEvgIAKMGXhJkASjJgoVVNjyEyAUQAeXADbsAJhAA8FavQA0UAOQOoAH0cBiBwD4mWZlCh8YHY4ATAAOm0CdDQMB2taOmcAMmSoAEIAbSd7B08AXXDaYzMIZFlIqSVmFmYufgooMEQUdCxaqmjpIREJKVkW5SU-AObFAG5-KAB6aagAPSIpzqgBxUrCGLiHYcwpgIDZg4DFqZYWIA

[obulat]

Thank you for the explanation!

[krysal]

Now I see! Thank you for this explanation, the example in the link made it crystal clear. The way Typescript works is interesting.

[dhruvkb]

This is great.

[obulat]

Tested using the instructions, works as you describe. LGTM!

[obulat]

Thank you for the explanation!