fix: allow more characters in the unicode range as component identifiers (#13198)

fixes #13194

We narrowed the allowed characters in #13057, but didn't take into account all possible (and for JavaScript identifiers allowed) unicode characters. This widens that, which also removes the accidental breaking change (because in Svelte 4 you were allowed to use these unicode characters).

.changeset/ten-singers-repair.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: allow more characters in the unicode range as component identifiers

packages/svelte/src/compiler/phases/1-parse/state/element.js

@@ -24,7 +24,9 @@ const regex_attribute_value = /^(?:"([^"]*)"|'([^'])*'|([^>\s]+))/;
 const regex_valid_element_name =
 	/^(?:![a-zA-Z]+|[a-zA-Z](?:[a-zA-Z0-9-]*[a-zA-Z0-9])?|[a-zA-Z][a-zA-Z0-9]*:[a-zA-Z][a-zA-Z0-9-]*[a-zA-Z0-9])$/;
 const regex_valid_component_name =
-	/^(?:[A-Z][A-Za-z0-9_$.]*|[a-z][A-Za-z0-9_$]*(?:\.[A-Za-z0-9_$]+)+)$/;
+	// https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Lexical_grammar#identifiers adjusted for our needs
+	// (must start with uppercase letter if no dots, can contain dots)
+	/^(?:\p{Lu}[$\u200c\u200d\p{ID_Continue}.]*|\p{ID_Start}[$\u200c\u200d\p{ID_Continue}]*(?:\.[$\u200c\u200d\p{ID_Continue}]+)+)$/u;
 
 /** @type {Map<string, ElementLike['type']>} */
 const root_only_meta_tags = new Map([

packages/svelte/tests/compiler-errors/samples/component-invalid-name/_config.js

@@ -5,6 +5,6 @@ export default test({
 		code: 'tag_invalid_name',
 		message:
 			'Expected a valid element or component name. Components must have a valid variable name or dot notation expression',
-		position: [1, 14]
+		position: [71, 84]
 	}
 });

packages/svelte/tests/compiler-errors/samples/component-invalid-name/main.svelte

@@ -1 +1,7 @@
+<!-- ok -->
+<Component />
+<Wunderschön />
+<Cæжαकン中 />
+
+<!-- error -->
 <Components[1] />