Merge branch 'issue-2291' of https://github.com/Panya/svelte into Panya-issue-2291

src/utils/names.ts

@@ -111,5 +111,9 @@ export function quote_prop_if_necessary(name: string) {
 }
 
 export function sanitize(name: string) {
-	return name.replace(/[^a-zA-Z]+/g, '_').replace(/^_/, '').replace(/_$/, '');
+	return name
+		.replace(/[^a-zA-Z0-9_]+/g, '_')
+		.replace(/^_/, '')
+		.replace(/_$/, '')
+		.replace(/^[0-9]/, '_$&');
 }

test/runtime/samples/slot-names/Nested.svelte

@@ -0,0 +1,6 @@
+<div>
+	<slot name="header1" />
+	<slot name="-header2_" />
+	<slot name="3header" />
+	<slot name="_header4" />
+</div>

test/runtime/samples/slot-names/_config.js

@@ -0,0 +1,10 @@
+export default {
+	html: `
+		<div>
+			<h1 slot="header1">Header 1</h1>
+			<h2 slot="-header2_">Header 2</h2>
+			<h3 slot="3header">Header 3</h3>
+			<h4 slot="_header4">Header 4</h4>
+		</div>
+	`
+};

test/runtime/samples/slot-names/main.svelte

@@ -0,0 +1,10 @@
+<script>
+	import Nested from './Nested.svelte';
+</script>
+
+<Nested>
+	<h1 slot="header1">Header 1</h1>
+	<h2 slot="-header2_">Header 2</h2>
+	<h3 slot="3header">Header 3</h3>
+	<h4 slot="_header4">Header 4</h4>
+</Nested>