From 7b3fd044e8e6dd8e573f4c858f6985f27d42cd4c Mon Sep 17 00:00:00 2001
From: NourBz <nour.benzarti@medtech.tn>
Date: Tue, 22 Apr 2025 21:18:03 +0100
Subject: [PATCH 1/2] fix(sequenceDiagram): allow empty message after colon
 (Fixes #6518)

---
 .../mermaid/src/diagrams/sequence/parser/sequenceDiagram.jison | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/packages/mermaid/src/diagrams/sequence/parser/sequenceDiagram.jison b/packages/mermaid/src/diagrams/sequence/parser/sequenceDiagram.jison
index 11b39d232..d2e81df5f 100644
--- a/packages/mermaid/src/diagrams/sequence/parser/sequenceDiagram.jison
+++ b/packages/mermaid/src/diagrams/sequence/parser/sequenceDiagram.jison
@@ -84,7 +84,8 @@ accDescr\s*"{"\s*                                { this.begin("acc_descr_multili
 \-\-[x]                                                         return 'DOTTED_CROSS';
 \-[\)]                                                          return 'SOLID_POINT';
 \-\-[\)]                                                        return 'DOTTED_POINT';
-":"(?:(?:no)?wrap:)?[^#\n;]+                                    return 'TXT';
+":"(?:(?:no)?wrap:)?[^#\n;]*                                    return 'TXT';
+":"                             								return 'TXT';
 "+"                                                             return '+';
 "-"                                                             return '-';
 <<EOF>>                                                         return 'NEWLINE';

From c17277e743b1c12e4134fba44c62a7d5885f2574 Mon Sep 17 00:00:00 2001
From: NourBz <nour.benzarti@medtech.tn>
Date: Tue, 22 Apr 2025 21:45:24 +0100
Subject: [PATCH 2/2] added changeset and unit test

---
 .changeset/sixty-deer-tell.md                    |  5 +++++
 .../diagrams/sequence/sequenceDiagram.spec.js    | 16 ++++++++++++++++
 2 files changed, 21 insertions(+)
 create mode 100644 .changeset/sixty-deer-tell.md

diff --git a/.changeset/sixty-deer-tell.md b/.changeset/sixty-deer-tell.md
new file mode 100644
index 000000000..fd48d2aea
--- /dev/null
+++ b/.changeset/sixty-deer-tell.md
@@ -0,0 +1,5 @@
+---
+'mermaid': major
+---
+
+fix: allow sequence diagram arrows with a trailing colon but no message
diff --git a/packages/mermaid/src/diagrams/sequence/sequenceDiagram.spec.js b/packages/mermaid/src/diagrams/sequence/sequenceDiagram.spec.js
index b21052ea6..c3b8c2b4a 100644
--- a/packages/mermaid/src/diagrams/sequence/sequenceDiagram.spec.js
+++ b/packages/mermaid/src/diagrams/sequence/sequenceDiagram.spec.js
@@ -2022,4 +2022,20 @@ describe('sequence db class', () => {
       expect(Object.hasOwn(sequenceDb, fun)).toBe(true);
     }
   });
+  // This test verifies that messages with a colon but no content (e.g., "Alice->>Bob:")
+  // are correctly parsed as valid messages with an empty string as the message content.
+
+  it('should parse a message with a trailing colon but no content', async () => {
+    const diagram = await Diagram.fromText(`
+sequenceDiagram
+Alice->>Bob:
+Bob->>Alice:Got it!
+`);
+
+    const messages = diagram.db.getMessages();
+    expect(messages.length).toBe(2);
+    expect(messages[0].message).toBe('');
+    expect(messages[0].from).toBe('Alice');
+    expect(messages[0].to).toBe('Bob');
+  });
 });