From ce9bdcc53f18603fcb6d7c4e53a977fed6bf11cc Mon Sep 17 00:00:00 2001
From: Zihua Li <i@zihua.li>
Date: Mon, 29 May 2023 21:00:37 +0800
Subject: [PATCH] Fix exceptions for empty lines

---
 cypress/integration/rendering/sequencediagram.spec.js | 10 ++++++++++
 packages/mermaid/src/utils.ts                         |  3 +++
 2 files changed, 13 insertions(+)

diff --git a/cypress/integration/rendering/sequencediagram.spec.js b/cypress/integration/rendering/sequencediagram.spec.js
index e5459637b..8ab21315f 100644
--- a/cypress/integration/rendering/sequencediagram.spec.js
+++ b/cypress/integration/rendering/sequencediagram.spec.js
@@ -88,6 +88,16 @@ context('Sequence diagram', () => {
       {}
     );
   });
+  it('should handle empty lines', () => {
+    imgSnapshotTest(
+      `
+      sequenceDiagram
+      Alice->>John: Hello John<br/>
+      John-->>Alice: Great!
+    `,
+      {}
+    );
+  });
   it('should handle line breaks and wrap annotations', () => {
     imgSnapshotTest(
       `
diff --git a/packages/mermaid/src/utils.ts b/packages/mermaid/src/utils.ts
index 6f824062d..3f70b2a7c 100644
--- a/packages/mermaid/src/utils.ts
+++ b/packages/mermaid/src/utils.ts
@@ -764,6 +764,9 @@ export const calculateTextDimensions: (
       let cheight = 0;
       const dim = { width: 0, height: 0, lineHeight: 0 };
       for (const line of lines) {
+        if (!line) {
+          continue;
+        }
         const textObj = getTextObj();
         textObj.text = line;
         const textElem = drawSimpleText(g, textObj)