fix(instrumentation-fastify): Support both CommonJS and ESM (open-tel…

…emetry#1519)

plugins/node/opentelemetry-instrumentation-fastify/package.json

@@ -12,7 +12,9 @@
     "lint:fix": "eslint . --ext .ts --fix",
     "precompile": "tsc --version && lerna run version:update --scope @opentelemetry/instrumentation-fastify --include-dependencies",
     "prepare": "npm run compile",
-    "test": "nyc ts-mocha -p tsconfig.json 'test/**/*.test.ts'",
+    "test:cjs": "nyc ts-mocha -p tsconfig.json 'test/**/*.test.ts'",
+    "test:esm": "nyc node --experimental-loader=@opentelemetry/instrumentation/hook.mjs ./node_modules/mocha/bin/mocha 'test/**/*.test.mjs'",
+    "test": "npm run test:cjs && npm run test:esm",
     "version:update": "node ../../../scripts/version-update.js",
     "prewatch": "npm run precompile",
     "watch": "tsc -w"

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

@@ -39,10 +39,17 @@ import {
   FastifyNames,
   FastifyTypes,
 } from './enums/AttributeNames';
-import type { HandlerOriginal, PluginFastifyReply } from './internal-types';
+import type {
+  CjsFastifyModuleExports,
+  EsmFastifyModuleExports,
+  FastifyModuleExports,
+  HandlerOriginal,
+  PluginFastifyReply,
+} from './internal-types';
 import type { FastifyInstrumentationConfig } from './types';
 import {
   endSpan,
+  isEsmFastifyModuleExports,
   safeExecuteInTheMiddleMaybePromise,
   startSpan,
 } from './utils';
@@ -197,24 +204,48 @@ export class FastifyInstrumentation extends InstrumentationBase {
     };
   }
 
-  private _patchConstructor(
-    original: () => FastifyInstance
-  ): () => FastifyInstance {
+  private _getPatchedFastifyInstance(module: () => FastifyInstance) {
     const instrumentation = this;
-    this._diag.debug('Patching fastify constructor function');
 
-    function fastify(this: FastifyInstance, ...args: any) {
-      const app: FastifyInstance = original.apply(this, args);
+    return function fastify(this: FastifyInstance, ...args: any) {
+      const app: FastifyInstance = module.apply(this, args);
       app.addHook('onRequest', instrumentation._hookOnRequest());
       app.addHook('preHandler', instrumentation._hookPreHandler());
 
       instrumentation._wrap(app, 'addHook', instrumentation._wrapAddHook());
 
       return app;
-    }
+    };
+  }
+
+  private _patchConstructor(
+    original: FastifyModuleExports
+  ): () => FastifyInstance {
+    this._diag.debug('Patching fastify constructor function');
+
+    return isEsmFastifyModuleExports(original)
+      ? this._patchConstructorInEsm(original)
+      : this._patchConstructorInCjs(original);
+  }
+
+  private _patchConstructorInEsm(
+    original: EsmFastifyModuleExports
+  ): () => FastifyInstance {
+    const fastify = this._getPatchedFastifyInstance(original.default);
+
+    this._wrap(original, 'default', () => fastify);
+    this._wrap(original, 'fastify', () => fastify);
+
+    return fastify;
+  }
+
+  private _patchConstructorInCjs(
+    original: CjsFastifyModuleExports
+  ): () => FastifyInstance {
+    const fastify = this._getPatchedFastifyInstance(original);
+
+    Object.assign(fastify, { default: fastify, fastify });
 
-    fastify.fastify = fastify;
-    fastify.default = fastify;
     return fastify;
   }
 

plugins/node/opentelemetry-instrumentation-fastify/src/internal-types.ts

@@ -15,11 +15,22 @@
  */
 
 import { Span } from '@opentelemetry/api';
-import type { FastifyReply } from 'fastify';
+import type { FastifyInstance, FastifyReply } from 'fastify';
 import { spanRequestSymbol } from './constants';
 
 export type HandlerOriginal = (() => Promise<unknown>) & (() => void);
 
 export type PluginFastifyReply = FastifyReply & {
   [spanRequestSymbol]?: Span[];
 };
+
+export type CjsFastifyModuleExports = () => FastifyInstance;
+
+export type EsmFastifyModuleExports = {
+  default: () => FastifyInstance;
+  fastify: () => FastifyInstance;
+};
+
+export type FastifyModuleExports =
+  | CjsFastifyModuleExports
+  | EsmFastifyModuleExports;

plugins/node/opentelemetry-instrumentation-fastify/src/utils.ts

@@ -22,7 +22,11 @@ import {
 } from '@opentelemetry/api';
 import { spanRequestSymbol } from './constants';
 
-import type { PluginFastifyReply } from './internal-types';
+import type {
+  EsmFastifyModuleExports,
+  FastifyModuleExports,
+  PluginFastifyReply,
+} from './internal-types';
 
 /**
  * Starts Span
@@ -137,3 +141,13 @@ function isPromise<T>(val: T | Promise<T>): val is Promise<T> {
     false
   );
 }
+
+/**
+ * Type guard for EsmFastifyModuleExports.
+ * @param module - Fastify's module exports.
+ */
+export function isEsmFastifyModuleExports(
+  module: FastifyModuleExports
+): module is EsmFastifyModuleExports {
+  return 'default' in module;
+}