use methodFactory extensions from the rootLogger in child loggers.

Author: toger5

src/logger.ts

@@ -15,7 +15,7 @@ See the License for the specific language governing permissions and
 limitations under the License.
 */
 
-import loglevel from "loglevel";
+import loglevel, { LoggingMethod } from "loglevel";
 
 /** Backwards-compatibility hack to expose `log` to applications that might still be relying on it. */
 interface LoggerWithLogMethod extends Logger {
@@ -135,7 +135,22 @@ function getPrefixedLogger(prefix?: string): LoggerWithLogMethod {
     if (prefixLogger.getChild === undefined) {
         // This is a new loglevel Logger which has not been turned into a PrefixedLogger yet.
         prefixLogger.prefix = prefix;
-        prefixLogger.getChild = (childPrefix): Logger => getPrefixedLogger((prefix ?? "") + childPrefix);
+        prefixLogger.getChild = (childPrefix): Logger => {
+            const childLogger = getPrefixedLogger((prefix ?? "") + childPrefix) as unknown as loglevel.Logger;
+            childLogger.methodFactory = (methodName, configLevel, loggerName): LoggingMethod => {
+                const method = (logger as unknown as loglevel.Logger).methodFactory(
+                    methodName,
+                    configLevel,
+                    loggerName,
+                );
+                return (...args): void => {
+                    method.apply(childLogger, args);
+                };
+            };
+            childLogger.setLevel(childLogger.getLevel());
+
+            return childLogger as unknown as Logger;
+        };
         prefixLogger.setLevel(loglevel.levels.DEBUG, false);
     }