Fix GlobalHttpHooks being registered twice when class is provided multiple times

When providing the same service multiple times with `useExisting`,
then discovered method would be listed twice.

Author: CarsonF

src/common/discovery-unique-methods.ts

@@ -0,0 +1,25 @@
+import { DiscoveredMethodWithMeta } from '@golevelup/nestjs-discovery';
+
+export const uniqueDiscoveredMethods = <T>(
+  methods: Array<DiscoveredMethodWithMeta<T>>,
+) => {
+  const seenClasses = new Map<object, Map<string, Set<unknown>>>();
+  const uniqueMethods = [] as typeof methods;
+  for (const method of methods) {
+    const clsInstance = method.discoveredMethod.parentClass.instance;
+    const methodName = method.discoveredMethod.methodName;
+    if (!seenClasses.has(clsInstance)) {
+      seenClasses.set(clsInstance, new Map());
+    }
+    const seenMethods = seenClasses.get(clsInstance)!;
+    if (!seenMethods.has(methodName)) {
+      seenMethods.set(methodName, new Set());
+    }
+    const seenMetadata = seenMethods.get(methodName)!;
+    if (!seenMetadata.has(method.meta)) {
+      seenMetadata.add(method.meta);
+      uniqueMethods.push(method);
+    }
+  }
+  return uniqueMethods;
+};

src/core/http/http.adapter.ts

@@ -15,6 +15,7 @@ import {
 import type { FastifyInstance, HTTPMethods, RouteOptions } from 'fastify';
 import rawBody from 'fastify-raw-body';
 import * as zlib from 'node:zlib';
+import { uniqueDiscoveredMethods } from '~/common/discovery-unique-methods';
 import { ConfigService } from '~/core/config/config.service';
 import {
   GlobalHttpHook,
@@ -73,7 +74,7 @@ export class HttpAdapter extends PatchedFastifyAdapter {
       .get(DiscoveryService)
       .providerMethodsWithMetaAtKey<keyof HttpHooks>(GlobalHttpHook.KEY);
     const fastify = app.getHttpAdapter().getInstance();
-    for (const globalHook of globalHooks) {
+    for (const globalHook of uniqueDiscoveredMethods(globalHooks)) {
       const handler = globalHook.discoveredMethod.handler.bind(
         globalHook.discoveredMethod.parentClass.instance,
       );