docs: Fixed root import name for typeVersions (#10180)

should be index.d.ts, not index

Co-authored-by: Willow (GHOST) <[email protected]>

---------

Co-authored-by: Willow (GHOST) <[email protected]>

Author: AdrianGonz97

.changeset/tiny-insects-repeat.md

@@ -0,0 +1,5 @@
+---
+'svelte-migrate': patch
+---
+
+fix: changed `index` to `index.d.ts` in `typesVersions`

documentation/docs/30-advanced/70-packaging.md

@@ -152,7 +152,7 @@ The second option is to (ab)use the `typesVersions` feature from TypeScript to w
 }
 ```
 
-`>4.0` tells TypeScript to check the inner map if the used TypeScript version is greater than 4 (which should in practice always be true). The inner map tells TypeScript that the typings for `your-library/foo` are found within `./dist/foo.d.ts`, which essentially replicates the `exports` condition. You also have `*` as a wildcard at your disposal to make many type definitions at once available without repeating yourself. Note that if you opt into `typesVersions` you have to declare all type imports through it, including the root import (which is defined as `"index": [..]`).
+`>4.0` tells TypeScript to check the inner map if the used TypeScript version is greater than 4 (which should in practice always be true). The inner map tells TypeScript that the typings for `your-library/foo` are found within `./dist/foo.d.ts`, which essentially replicates the `exports` condition. You also have `*` as a wildcard at your disposal to make many type definitions at once available without repeating yourself. Note that if you opt into `typesVersions` you have to declare all type imports through it, including the root import (which is defined as `"index.d.ts": [..]`).
 
 You can read more about that feature [here](https://www.typescriptlang.org/docs/handbook/declaration-files/publishing.html#version-selection-with-typesversions).
 

packages/migrate/migrations/package/migrate_pkg.js

@@ -114,7 +114,7 @@ export function update_pkg_json(config, pkg, files) {
 			}`;
 
 			if (has_type) {
-				const type_key = key.slice(2) || 'index';
+				const type_key = key.slice(2) || 'index.d.ts';
 				if (!pkg.exports[key]) {
 					types_versions[type_key] = [out_dir_type_path];
 				} else {
@@ -191,7 +191,7 @@ export function update_pkg_json(config, pkg, files) {
 	// A hack to get around the limitation that TS doesn't support "exports" field  with moduleResolution: 'node'
 	if (
 		Object.keys(types_versions).length > 1 ||
-		(Object.keys(types_versions).length > 0 && !types_versions['index'])
+		(Object.keys(types_versions).length > 0 && !types_versions['index.d.ts'])
 	) {
 		pkg.typesVersions = { '>4.0': types_versions };
 	}

packages/migrate/migrations/package/migrate_pkg.spec.js

@@ -94,7 +94,7 @@ test('Updates package.json', () => {
 		svelte: './package/index.js',
 		typesVersions: {
 			'>4.0': {
-				index: ['./package/index.d.ts'],
+				'index.d.ts': ['./package/index.d.ts'],
 				'foo/Bar.svelte': ['./package/foo/Bar.svelte.d.ts'],
 				baz: ['./package/baz.d.ts'],
 				bar: ['./package/bar/index.d.ts'],