feat: add inline alias attribute support for participants and actors in sequence diagrams

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

cypress/integration/rendering/sequencediagram-v2.spec.js

@@ -899,5 +899,71 @@ describe('Sequence Diagram Special Cases', () => {
         );
       });
     });
+
+    describe('Participant Inline Alias in Config', () => {
+      it('should render participants with inline alias in config object', () => {
+        imgSnapshotTest(
+          `sequenceDiagram
+          participant API@{ "type" : "boundary", "alias": "Public API" }
+          participant Auth@{ "type" : "control", "alias": "Auth Service" }
+          participant DB@{ "type" : "database", "alias": "User DB" }
+          API ->> Auth: Login request
+          Auth ->> DB: Query user
+          DB -->> Auth: User data
+          Auth -->> API: Token`,
+          { look: 'classic', sequence: { diagramMarginX: 50, diagramMarginY: 10 } }
+        );
+      });
+
+      it('should render actors with inline alias in config object', () => {
+        imgSnapshotTest(
+          `sequenceDiagram
+          actor U@{ "type" : "actor", "alias": "End User" }
+          actor G@{ "type" : "boundary", "alias": "Gateway" }
+          actor S@{ "type" : "control", "alias": "Service" }
+          U ->> G: Request
+          G ->> S: Process
+          S -->> G: Response
+          G -->> U: Result`,
+          { look: 'classic', sequence: { diagramMarginX: 50, diagramMarginY: 10 } }
+        );
+      });
+
+      it('should handle mixed inline and external alias syntax', () => {
+        imgSnapshotTest(
+          `sequenceDiagram
+          participant A@{ "type" : "boundary", "alias": "Service A" }
+          participant B@{ "type" : "control" } as Service B
+          participant C@{ "type" : "database" }
+          A ->> B: Request
+          B ->> C: Query
+          C -->> B: Data
+          B -->> A: Response`,
+          { look: 'classic', sequence: { diagramMarginX: 50, diagramMarginY: 10 } }
+        );
+      });
+
+      it('should prioritize external alias over inline alias', () => {
+        imgSnapshotTest(
+          `sequenceDiagram
+          participant API@{ "type" : "boundary", "alias": "Internal Name" } as External Name
+          participant DB@{ "type" : "database", "alias": "Internal DB" } AS External DB
+          API ->> DB: Query
+          DB -->> API: Result`,
+          { look: 'classic', sequence: { diagramMarginX: 50, diagramMarginY: 10 } }
+        );
+      });
+
+      it('should render inline alias with only alias field (no type)', () => {
+        imgSnapshotTest(
+          `sequenceDiagram
+          participant API@{ "alias": "Public API" }
+          participant Auth@{ "alias": "Auth Service" }
+          API ->> Auth: Request
+          Auth -->> API: Response`,
+          { look: 'classic', sequence: { diagramMarginX: 50, diagramMarginY: 10 } }
+        );
+      });
+    });
   });
 });

packages/mermaid/src/diagrams/sequence/sequenceDb.ts

@@ -172,6 +172,12 @@ export class SequenceDB implements DiagramDB {
       doc = yaml.load(yamlData, { schema: yaml.JSON_SCHEMA }) as ParticipantMetaData;
     }
     type = doc?.type ?? type;
+
+    // If alias is provided in metadata and description is not already set, use the alias
+    if (doc?.alias && (!description || description.text === name)) {
+      description = { text: doc.alias, wrap: description?.wrap, type };
+    }
+
     const old = this.state.records.actors.get(id);
     if (old) {
       // If already set and trying to set to a new one throw error

packages/mermaid/src/diagrams/sequence/sequenceDiagram.spec.js

@@ -2661,5 +2661,74 @@ Bob->>Alice:Got it!
       expect(actors.get('API').type).toBe('boundary');
       expect(actors.get('API').description).toBe('Public API');
     });
+
+    it('should parse participant with inline alias in config object', async () => {
+      const diagram = await Diagram.fromText(`
+      sequenceDiagram
+      participant API@{ "type" : "boundary", "alias": "Public API" }
+      participant Auth@{ "type" : "control", "alias": "Auth Controller" }
+      API->>Auth: Request
+      Auth-->>API: Response
+      `);
+      const actors = diagram.db.getActors();
+      expect(actors.get('API').type).toBe('boundary');
+      expect(actors.get('API').description).toBe('Public API');
+      expect(actors.get('Auth').type).toBe('control');
+      expect(actors.get('Auth').description).toBe('Auth Controller');
+    });
+
+    it('should parse actor with inline alias in config object', async () => {
+      const diagram = await Diagram.fromText(`
+      sequenceDiagram
+      actor U@{ "type" : "actor", "alias": "End User" }
+      actor DB@{ "type" : "database", "alias": "User Database" }
+      U->>DB: Query
+      DB-->>U: Result
+      `);
+      const actors = diagram.db.getActors();
+      expect(actors.get('U').type).toBe('actor');
+      expect(actors.get('U').description).toBe('End User');
+      expect(actors.get('DB').type).toBe('database');
+      expect(actors.get('DB').description).toBe('User Database');
+    });
+
+    it('should prioritize external alias over inline alias', async () => {
+      const diagram = await Diagram.fromText(`
+      sequenceDiagram
+      participant API@{ "type" : "boundary", "alias": "Internal Name" } as External Name
+      API->>API: test
+      `);
+      const actors = diagram.db.getActors();
+      expect(actors.get('API').type).toBe('boundary');
+      expect(actors.get('API').description).toBe('External Name');
+    });
+
+    it('should handle participant with only inline alias (no type)', async () => {
+      const diagram = await Diagram.fromText(`
+      sequenceDiagram
+      participant API@{ "alias": "Public API" }
+      API->>API: test
+      `);
+      const actors = diagram.db.getActors();
+      expect(actors.get('API').description).toBe('Public API');
+    });
+
+    it('should handle mixed inline and external alias syntax', async () => {
+      const diagram = await Diagram.fromText(`
+      sequenceDiagram
+      participant A@{ "type" : "boundary", "alias": "Service A" }
+      participant B@{ "type" : "control" } as Service B
+      participant C@{ "type" : "database" }
+      A->>B: Request
+      B->>C: Query
+      `);
+      const actors = diagram.db.getActors();
+      expect(actors.get('A').type).toBe('boundary');
+      expect(actors.get('A').description).toBe('Service A');
+      expect(actors.get('B').type).toBe('control');
+      expect(actors.get('B').description).toBe('Service B');
+      expect(actors.get('C').type).toBe('database');
+      expect(actors.get('C').description).toBe('C');
+    });
   });
 });

packages/mermaid/src/types.ts

@@ -23,6 +23,7 @@ export interface ParticipantMetaData {
     | 'database'
     | 'collections'
     | 'queue';
+  alias?: string;
 }
 
 export interface EdgeMetaData {