From ae2c1133253192179ea33236ff8ca059800e155d Mon Sep 17 00:00:00 2001
From: Tony Garnock-Jones <tonyg@leastfixedpoint.com>
Date: Sat, 2 Dec 2023 19:35:36 +0100
Subject: [PATCH] Error check in case of multiple nodes generated

---
 packages/html2/src/index.ts | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/packages/html2/src/index.ts b/packages/html2/src/index.ts
index 9401169..9633941 100644
--- a/packages/html2/src/index.ts
+++ b/packages/html2/src/index.ts
@@ -39,7 +39,14 @@ export class Widget implements EventTarget {
 
         dataflow {
             const oldNode = this.node.value;
-            const newNode = template`${this.nodeGenerator(template)}`.node();
+
+            const fragments = template`${this.nodeGenerator(template)}`;
+            const newNodes = fragments.nodes();
+            if (newNodes.length > 1) {
+                throw new Error(`@syndicate-lang/html2: Multiple nodes returned from template: ${fragments.toString()}`);
+            }
+            const newNode = newNodes[0];
+
             if (oldNode !== newNode) {
                 if (oldNode !== null) {
                     for (const [type, cbs] of this.callbacks.entries()) {