fix(instrumentation-hapi): fix this binding for plugin register method (#2625)

Author: seemk

plugins/node/opentelemetry-instrumentation-hapi/src/instrumentation.ts

@@ -267,9 +267,13 @@ export class HapiInstrumentation extends InstrumentationBase {
   private _wrapRegisterHandler<T>(plugin: Hapi.Plugin<T>): void {
     const instrumentation: HapiInstrumentation = this;
     const pluginName = getPluginName(plugin);
-    const oldHandler = plugin.register;
+    const oldRegister = plugin.register;
     const self = this;
-    const newRegisterHandler = function (server: Hapi.Server, options: T) {
+    const newRegisterHandler = function (
+      this: typeof plugin,
+      server: Hapi.Server,
+      options: T
+    ) {
       self._wrap(server, 'route', original => {
         return instrumentation._getServerRoutePatch.bind(instrumentation)(
           original,
@@ -287,7 +291,7 @@ export class HapiInstrumentation extends InstrumentationBase {
           pluginName
         );
       });
-      return oldHandler(server, options);
+      return oldRegister.call(this, server, options);
     };
     plugin.register = newRegisterHandler;
   }

plugins/node/opentelemetry-instrumentation-hapi/test/hapi-plugin.test.ts

@@ -81,12 +81,13 @@ describe('Hapi Instrumentation - Hapi.Plugin Tests', () => {
     name: 'simplePlugin',
     version: '1.0.0',
     multiple: true,
+    value: 42,
     register: async function (server: hapi.Server, options: any) {
       server.route({
         method: 'GET',
         path: '/hello',
-        handler: function (request, h) {
-          return `hello, world, ${options.name}`;
+        handler: (request, h) => {
+          return `hello, world, ${this.value} ${options.name}`;
         },
       });
     },