feat: debug log global registrations and logger overwrites

Author: rauno56

src/api/diag.ts

@@ -79,11 +79,15 @@ export class DiagAPI implements DiagLogger {
         return false;
       }
 
-      return registerGlobal(
-        'diag',
-        createLogLevelDiagLogger(logLevel, logger),
-        true
-      );
+      const oldLogger = getGlobal('diag');
+      const newLogger = createLogLevelDiagLogger(logLevel, logger);
+      // There already is an logger registered. We'll let it know before overwriting it.
+      if (oldLogger) {
+        oldLogger.warn('Current logger will be overwritten');
+        newLogger.warn('Current logger will overwrite one already registered');
+      }
+
+      return registerGlobal('diag', newLogger, true);
     };
 
     self.disable = () => {

src/internal/global-utils.ts

@@ -35,13 +35,16 @@ export function registerGlobal<Type extends keyof OTelGlobalAPI>(
   instance: OTelGlobalAPI[Type],
   allowOverride = false
 ): boolean {
-  _global[GLOBAL_OPENTELEMETRY_API_KEY] = _global[
+  diag.debug(
+    `@opentelemetry/api: Registering a global for ${type} v${VERSION}.`
+  );
+
+  const api = (_global[GLOBAL_OPENTELEMETRY_API_KEY] = _global[
     GLOBAL_OPENTELEMETRY_API_KEY
   ] ?? {
     version: VERSION,
-  };
+  });
 
-  const api = _global[GLOBAL_OPENTELEMETRY_API_KEY]!;
   if (!allowOverride && api[type]) {
     // already registered an API of this type
     const err = new Error(
@@ -75,6 +78,9 @@ export function getGlobal<Type extends keyof OTelGlobalAPI>(
 }
 
 export function unregisterGlobal(type: keyof OTelGlobalAPI) {
+  diag.debug(
+    `@opentelemetry/api: Unregistering a global for ${type} v${VERSION}.`
+  );
   const api = _global[GLOBAL_OPENTELEMETRY_API_KEY];
 
   if (api) {