From 08de4bed6f53479bf76b8482706fb3df1ae73647 Mon Sep 17 00:00:00 2001
From: Michael Bleigh <bleigh@google.com>
Date: Thu, 8 Aug 2024 19:20:05 -0700
Subject: [PATCH] Persist Handlebars in global to keep it through HMR. Fixes
 #744 (#762)

---
 js/plugins/dotprompt/src/template.ts | 4 +++-
 1 file changed, 3 insertions(+), 1 deletion(-)

diff --git a/js/plugins/dotprompt/src/template.ts b/js/plugins/dotprompt/src/template.ts
index 7ff16f78f..020f9fad9 100644
--- a/js/plugins/dotprompt/src/template.ts
+++ b/js/plugins/dotprompt/src/template.ts
@@ -19,7 +19,9 @@ import { DocumentData } from '@genkit-ai/ai/retriever';
 import Handlebars from 'handlebars';
 import { PromptMetadata } from './metadata.js';
 
-const Promptbars = Handlebars.create();
+const Promptbars: typeof Handlebars =
+  global['dotprompt.handlebars'] || Handlebars.create();
+global['dotprompt.handlebars'] = Promptbars;
 
 function jsonHelper(serializable: any, options: { hash: { indent?: number } }) {
   return new Promptbars.SafeString(