prevent commas in attributes - fixes #3341

src/compiler/compile/render_dom/wrappers/Element/Attribute.ts

@@ -240,7 +240,7 @@ export default class AttributeWrapper {
 			return chunk.type === 'Text'
 				? chunk.data.replace(/"/g, '\\"')
 				: `\${${chunk.render()}}`;
-		})}"`;
+		}).join('')}"`;
 	}
 }
 

test/runtime/samples/innerhtml-interpolated-literal/_config.js

@@ -0,0 +1,7 @@
+export default {
+	html: `
+		<div>
+			<span class="a/42"/>
+		</div>
+	`
+}

test/runtime/samples/innerhtml-interpolated-literal/main.svelte

@@ -0,0 +1,3 @@
+<div>
+	<span class="a/{42}"/>
+</div>