From 299226f8c22101fe59d08e05b4e47abf336859ae Mon Sep 17 00:00:00 2001
From: darshanr0107 <darshan@mermaidchart.com>
Date: Wed, 20 Aug 2025 18:36:45 +0530
Subject: [PATCH] fix: relationship label to be optional in ER diagram syntax

on-behalf-of: @Mermaid-Chart <hello@mermaidchart.com>
---
 .../integration/rendering/erDiagram.spec.js   | 12 +++++++
 .../src/diagrams/er/parser/erDiagram.jison    | 34 ++++++++++++++-----
 .../src/diagrams/er/parser/erDiagram.spec.js  |  6 ++++
 3 files changed, 44 insertions(+), 8 deletions(-)

diff --git a/cypress/integration/rendering/erDiagram.spec.js b/cypress/integration/rendering/erDiagram.spec.js
index 8f6193f96..7d59a5793 100644
--- a/cypress/integration/rendering/erDiagram.spec.js
+++ b/cypress/integration/rendering/erDiagram.spec.js
@@ -322,6 +322,18 @@ ORDER ||--|{ LINE-ITEM : contains
     );
   });
 
+  it('should render an ER diagram  without labels also', () => {
+    imgSnapshotTest(
+      `
+    erDiagram
+        BOOK }|..|{ AUTHOR 
+        BOOK }|..|{ GENRE
+        AUTHOR }|..|{ GENRE 
+      `,
+      { logLevel: 1 }
+    );
+  });
+
   it('should render relationship labels with line breaks', () => {
     imgSnapshotTest(
       `
diff --git a/packages/mermaid/src/diagrams/er/parser/erDiagram.jison b/packages/mermaid/src/diagrams/er/parser/erDiagram.jison
index 2b59309fb..d3f5c0683 100644
--- a/packages/mermaid/src/diagrams/er/parser/erDiagram.jison
+++ b/packages/mermaid/src/diagrams/er/parser/erDiagram.jison
@@ -94,6 +94,22 @@ start
     : 'ER_DIAGRAM' document 'EOF' { /*console.log('finished parsing');*/ }
     ;
 
+relationship
+  : ENTITY relationType ENTITY maybeRole
+    {
+      yy.addRelationship($1, $4, $3, $2);
+    };
+
+maybeRole
+  : COLON role
+    {
+      $$ = $2;
+    }
+  | /* empty */
+    {
+      $$ = '';
+    };
+
 document
 	: /* empty */ { $$ = [] }
 	| document line {$1.push($2);$$ = $1}
@@ -108,32 +124,34 @@ line
 
 
 statement
-    : entityName relSpec entityName COLON role
+    : entityName relSpec entityName maybeRole
       {
           yy.addEntity($1);
           yy.addEntity($3);
-          yy.addRelationship($1, $5, $3, $2);
+          yy.addRelationship($1, $4, $3, $2);
       }
-    | entityName STYLE_SEPARATOR idList relSpec entityName STYLE_SEPARATOR idList COLON role
+    | entityName STYLE_SEPARATOR idList relSpec entityName STYLE_SEPARATOR idList maybeRole
+
       {
           yy.addEntity($1);
           yy.addEntity($5);
-          yy.addRelationship($1, $9, $5, $4);
+          yy.addRelationship($1, $8, $5, $4);
           yy.setClass([$1], $3);
           yy.setClass([$5], $7);
       }
-    | entityName STYLE_SEPARATOR idList relSpec entityName COLON role
+    | entityName STYLE_SEPARATOR idList relSpec entityName maybeRole
+
       {
           yy.addEntity($1);
           yy.addEntity($5);
-          yy.addRelationship($1, $7, $5, $4);
+          yy.addRelationship($1, $6, $5, $4);
           yy.setClass([$1], $3);
       }
-    | entityName relSpec entityName STYLE_SEPARATOR idList COLON role
+    | entityName relSpec entityName STYLE_SEPARATOR idList maybeRole
       {
           yy.addEntity($1);
           yy.addEntity($3);
-          yy.addRelationship($1, $7, $3, $2);
+          yy.addRelationship($1, $6, $3, $2);
           yy.setClass([$3], $5);
       }
     | entityName BLOCK_START attributes BLOCK_STOP
diff --git a/packages/mermaid/src/diagrams/er/parser/erDiagram.spec.js b/packages/mermaid/src/diagrams/er/parser/erDiagram.spec.js
index fd1d2a9e5..aabedfd17 100644
--- a/packages/mermaid/src/diagrams/er/parser/erDiagram.spec.js
+++ b/packages/mermaid/src/diagrams/er/parser/erDiagram.spec.js
@@ -981,6 +981,12 @@ describe('when parsing ER diagram it...', function () {
       expect(rels[0].roleA).toBe('places');
     });
 
+    it('should allow label as optional', function () {
+      erDiagram.parser.parse('erDiagram\nCUSTOMER ||--|{ ORDER');
+      const rels = erDb.getRelationships();
+      expect(rels[0].roleA).toBe('');
+    });
+
     it('should represent parent-child relationship correctly', function () {
       erDiagram.parser.parse('erDiagram\nPROJECT u--o{ TEAM_MEMBER : "parent"');
       const rels = erDb.getRelationships();