From f6682fe3ac82ab15082c8fb988a73cbd48803488 Mon Sep 17 00:00:00 2001
From: Dayuan Jiang <34411969+DayuanJiang@users.noreply.github.com>
Date: Mon, 8 Dec 2025 10:10:52 +0900
Subject: [PATCH] fix(diagram): wrap XML in mxfile structure when canvas is
 empty (#156)

When clicking an example diagram on a clean page (no existing diagram),
the code was passing raw <root>...</root> format XML directly to DrawIO.
However, DrawIO expects the full mxfile/diagram/mxGraphModel/root structure.

This fix provides a default mxfile template when chartXML is empty,
ensuring replaceNodes properly wraps the content before loading into DrawIO.

Co-authored-by: dayuan.jiang <jiangdy@amazon.co.jp>
---
 components/chat-message-display.tsx | 10 ++++++----
 1 file changed, 6 insertions(+), 4 deletions(-)

diff --git a/components/chat-message-display.tsx b/components/chat-message-display.tsx
index 3c618ef..73fc11b 100644
--- a/components/chat-message-display.tsx
+++ b/components/chat-message-display.tsx
@@ -177,10 +177,12 @@ export function ChatMessageDisplay({
             const currentXml = xml || ""
             const convertedXml = convertToLegalXml(currentXml)
             if (convertedXml !== previousXML.current) {
-                // If chartXML is empty, use the converted XML directly
-                const replacedXML = chartXML
-                    ? replaceNodes(chartXML, convertedXml)
-                    : convertedXml
+                // If chartXML is empty, create a default mxfile structure to use with replaceNodes
+                // This ensures the XML is properly wrapped in mxfile/diagram/mxGraphModel format
+                const baseXML =
+                    chartXML ||
+                    `<mxfile><diagram name="Page-1" id="page-1"><mxGraphModel><root><mxCell id="0"/><mxCell id="1" parent="0"/></root></mxGraphModel></diagram></mxfile>`
+                const replacedXML = replaceNodes(baseXML, convertedXml)
 
                 const validationError = validateMxCellStructure(replacedXML)
                 if (!validationError) {