fix: handle newline characters as whitespace

on-behalf-of: @Mermaid-Chart <hello@mermaidchart.com>

cypress/integration/rendering/classDiagram.spec.js

@@ -524,5 +524,18 @@ describe('Class diagram', () => {
       `,
       {}
     );
+    it('should handle an empty class body with empty braces', () => {
+      imgSnapshotTest(
+        ` classDiagram
+        class FooBase~T~ {}
+    class Bar {
+        +Zip
+        +Zap()
+    }
+    FooBase <|-- Ba
+        `,
+        { flowchart: { defaultRenderer: 'elk' } }
+      );
+    });
   });
 });

packages/mermaid/src/diagrams/class/classDiagram.spec.ts

@@ -1070,6 +1070,14 @@ describe('given a class diagram with members and methods ', function () {
 
       parser.parse(str);
     });
+    it('should handle an empty class body with {}', function () {
+      const str = 'classDiagram\nclass EmptyClass {}';
+      parser.parse(str);
+      const actual = parser.yy.getClass('EmptyClass');
+      expect(actual.label).toBe('EmptyClass');
+      expect(actual.members.length).toBe(0);
+      expect(actual.methods.length).toBe(0);
+    });
   });
 });
 

packages/mermaid/src/diagrams/class/parser/classDiagram.jison

@@ -293,6 +293,7 @@ classStatement
     : classIdentifier
     | classIdentifier STYLE_SEPARATOR alphaNumToken      {yy.setCssClass($1, $3);}
     | classIdentifier STRUCT_START members STRUCT_STOP   {yy.addMembers($1,$3);}
+    | classIdentifier STRUCT_START STRUCT_STOP           {}
     | classIdentifier STYLE_SEPARATOR alphaNumToken STRUCT_START members STRUCT_STOP {yy.setCssClass($1, $3);yy.addMembers($1,$5);}
     ;
 
@@ -301,6 +302,13 @@ classIdentifier
     | CLASS className classLabel                         {$$=$2; yy.addClass($2);yy.setClassLabel($2, $3);}
     ;
 
+
+emptyBody
+    :
+    | SPACE emptyBody
+    | NEWLINE emptyBody
+    ;
+
 annotationStatement
     : ANNOTATION_START alphaNumToken ANNOTATION_END className  { yy.addAnnotation($4,$2); }
     ;