fix(c4): allow '#' in title and accDescription

.changeset/c4-title-hash.md

@@ -0,0 +1,5 @@
+---
+'mermaid': patch
+---
+
+fix(c4): allow `#` in a C4 `title` and `accDescription`

packages/mermaid/src/diagrams/c4/parser/c4Diagram.jison

@@ -84,8 +84,8 @@
 .*direction\s+LR[^\n]*                    return 'direction_lr';
 
 
-"title"\s[^#\n;]+                         return 'title';
-"accDescription"\s[^#\n;]+                return 'accDescription';
+"title"\s[^\n;]+                          return 'title';
+"accDescription"\s[^\n;]+                 return 'accDescription';
 accTitle\s*":"\s*                         { this.begin("acc_title");return 'acc_title'; }
 <acc_title>(?!\n|;|#)*[^\n]*              { this.popState(); return "acc_title_value"; }
 accDescr\s*":"\s*                         { this.begin("acc_descr");return 'acc_descr'; }

packages/mermaid/src/diagrams/c4/parser/c4Diagram.spec.ts

@@ -39,6 +39,22 @@ Person(Person, "Person", "Person")`);
     expect(onlyShape.label.text).toBe('Person');
   });
 
+  it('should allow a # in the title', function () {
+    c4.parser.parse(`C4Context
+title Relationship to a boundary (#4864)
+Person(Person, "Person", "Person")`);
+
+    expect(c4.parser.yy.getTitle()).toBe('Relationship to a boundary (#4864)');
+  });
+
+  it('should allow a # in the accDescription', function () {
+    c4.parser.parse(`C4Context
+accDescription Context diagram for issue #4864
+Person(Person, "Person", "Person")`);
+
+    expect(c4.parser.yy.getAccDescription()).toBe('Context diagram for issue #4864');
+  });
+
   it('should allow default in the parameters', function () {
     c4.parser.parse(`C4Context
 Person(default, "default", "default")`);