fix(common): when passing class functions to logger methods

packages/common/services/console-logger.service.ts

@@ -245,10 +245,18 @@ export class ConsoleLogger implements LoggerService {
   }
 
   protected stringifyMessage(message: unknown, logLevel: LogLevel) {
-    // If the message is a function, call it and re-resolve its value.
-    return isFunction(message)
-      ? this.stringifyMessage(message(), logLevel)
-      : isPlainObject(message) || Array.isArray(message)
+    if (isFunction(message)) {
+      const messageAsStr = Function.prototype.toString.call(message);
+      const isClass = messageAsStr.startsWith('class ');
+      if (isClass) {
+        // If the message is a class, we will display the class name.
+        return this.stringifyMessage(message.name, logLevel);
+      }
+      // If the message is a non-class function, call it and re-resolve its value.
+      return this.stringifyMessage(message(), logLevel);
+    }
+
+    return isPlainObject(message) || Array.isArray(message)
       ? `${this.colorize('Object:', logLevel)}\n${JSON.stringify(
           message,
           (key, value) =>

packages/common/test/services/logger.service.spec.ts

@@ -298,6 +298,34 @@ describe('Logger', () => {
         );
       });
     });
+
+    describe('classes for message', () => {
+      let processStdoutWriteSpy: sinon.SinonSpy;
+
+      beforeEach(() => {
+        processStdoutWriteSpy = sinon.spy(process.stdout, 'write');
+      });
+      afterEach(() => {
+        processStdoutWriteSpy.restore();
+      });
+
+      it("should display class's name or empty for anonymous classes", () => {
+        const logger = new ConsoleLogger();
+
+        // in-line anonymous class
+        logger.log(class {});
+
+        // named class
+        class Test {
+          #privateField = 'private field';
+          publicField = 'public field';
+        }
+        logger.log(Test);
+
+        expect(processStdoutWriteSpy.firstCall.firstArg).to.include('');
+        expect(processStdoutWriteSpy.secondCall.firstArg).to.include(Test.name);
+      });
+    });
   });
 
   describe('[instance methods]', () => {