feat: add getSingletonInstance alias to singleton.get(id) (#5216)

Co-authored-by: William.Tung <[email protected]>

Author: fengmk2

lib/core/singleton.js

@@ -79,6 +79,11 @@ class Singleton {
     return this.clients.get(id);
   }
 
+  // alias to `get(id)`
+  getSingletonInstance(id) {
+    return this.clients.get(id);
+  }
+
   createInstance(config, clientName) {
     // async creator only support createInstanceAsync
     assert(!is.asyncFunction(this.create),

test/lib/core/singleton.test.js

@@ -115,7 +115,11 @@ describe('test/lib/core/singleton.test.js', () => {
       singleton.init();
       assert(app.dataService instanceof Singleton);
       assert(app.dataService.get('first').config.foo === 'bar1');
+      assert(app.dataService.getSingletonInstance('first').config.foo === 'bar1');
+      assert(app.dataService.get('first'), app.dataService.getSingletonInstance('first'));
       assert(app.dataService.get('second').config.foo === 'bar');
+      assert(app.dataService.getSingletonInstance('second').config.foo === 'bar');
+      assert(app.dataService.get('second'), app.dataService.getSingletonInstance('second'));
       assert(typeof app.dataService.createInstance === 'function');
     });