fix: allow self-closing tags within math namespace

fixes #15757

.changeset/wicked-cheetahs-juggle.md

@@ -0,0 +1,5 @@
+---
+'svelte': patch
+---
+
+fix: allow self-closing tags within math namespace

packages/svelte/src/compiler/phases/2-analyze/visitors/RegularElement.js

@@ -173,7 +173,8 @@ export function RegularElement(node, context) {
 	if (
 		context.state.analysis.source[node.end - 2] === '/' &&
 		!is_void(node_name) &&
-		!is_svg(node_name)
+		!is_svg(node_name) &&
+		!is_mathml(node_name)
 	) {
 		w.element_invalid_self_closing_tag(node, node.name);
 	}

packages/svelte/tests/validator/samples/invalid-self-closing-tag/input.svelte

@@ -1,6 +1,7 @@
 <!-- valid -->
 <link />
 <svg><g /></svg>
+<math><mspace /></math>
 <enhanced:img />
 
 

packages/svelte/tests/validator/samples/invalid-self-closing-tag/warnings.json

@@ -3,11 +3,11 @@
 		"code": "element_invalid_self_closing_tag",
 		"message": "Self-closing HTML tags for non-void elements are ambiguous — use `<div ...></div>` rather than `<div ... />`",
 		"start": {
-			"line": 8,
+			"line": 9,
 			"column": 0
 		},
 		"end": {
-			"line": 8,
+			"line": 9,
 			"column": 7
 		}
 	},
@@ -15,11 +15,11 @@
 		"code": "element_invalid_self_closing_tag",
 		"message": "Self-closing HTML tags for non-void elements are ambiguous — use `<my-thing ...></my-thing>` rather than `<my-thing ... />`",
 		"start": {
-			"line": 9,
+			"line": 10,
 			"column": 0
 		},
 		"end": {
-			"line": 9,
+			"line": 10,
 			"column": 12
 		}
 	}