fix: validate form inside a form

Author: paoloricciuti

.changeset/breezy-waves-camp.md

@@ -0,0 +1,5 @@
+---
+"svelte": patch
+---
+
+fix: validate form inside a form

packages/svelte/src/constants.js

@@ -118,7 +118,8 @@ export const interactive_elements = new Set([
 	'iframe',
 	'embed',
 	'select',
-	'textarea'
+	'textarea',
+	'form'
 ]);
 
 export const disallowed_paragraph_contents = [

packages/svelte/tests/validator/samples/invalid-node-placement-4/errors.json

@@ -0,0 +1,14 @@
+[
+	{
+		"code": "node_invalid_placement",
+		"message": "<form> is invalid inside <form>",
+		"start": {
+			"line": 4,
+			"column": 3
+		},
+		"end": {
+			"line": 6,
+			"column": 10
+		}
+	}
+]

packages/svelte/tests/validator/samples/invalid-node-placement-4/input.svelte

@@ -0,0 +1,9 @@
+<div>
+	<form>
+		<div>
+			<form>
+				<input />
+			</form>
+		</div>
+	</form>
+</div>