fn.default check for transpiled modules (#61)

* fn.default check for transpiled modules

More info in issue #60

* lint fix (oops)

* Unit test for ECMAScript module

* Apply suggestions from code review

Co-Authored-By: nurdism <craigbett@gmail.com>

* Apply suggestions from @delvedor

* Apply suggestions from @Ethan-Arrowood

fastify-plugin.d.ts

@@ -12,7 +12,7 @@ import * as fastify from 'fastify';
  * @param next The `next` callback is not available when using `async`/`await`. If you do invoke a `next` callback in this situation unexpected behavior may occur.
  */
 declare function fastifyPlugin<HttpServer, HttpRequest, HttpResponse, T>(
-  fn: fastify.Plugin<HttpServer, HttpRequest, HttpResponse, T>,
+  fn: fastify.Plugin<HttpServer, HttpRequest, HttpResponse, T> | { default: fastify.Plugin<HttpServer, HttpRequest, HttpResponse, T> },
   options?: fastifyPlugin.PluginOptions | string,
   next?: fastifyPlugin.nextCallback
 ): fastify.Plugin<HttpServer, HttpRequest, HttpResponse, T>;

index.js

@@ -5,6 +5,10 @@ const console = require('console')
 const extractPluginName = require('./stackParser')
 
 function plugin (fn, options = {}) {
+  if (typeof fn.default !== 'undefined') { // Support for 'export default' behaviour in transpiled ECMAScript module
+    fn = fn.default
+  }
+
   if (typeof fn !== 'function') {
     throw new TypeError(`fastify-plugin expects a function, instead got a '${typeof fn}'`)
   }

test/test.js

@@ -22,6 +22,21 @@ test('should return the function with the skip-override Symbol', t => {
   t.ok(plugin[Symbol.for('skip-override')])
 })
 
+test('should support "default" function from babel module', t => {
+  t.plan(1)
+
+  const plugin = {
+    default: () => {}
+  }
+
+  try {
+    fp(plugin)
+    t.pass()
+  } catch (e) {
+    t.is(e.message, 'fastify-plugin expects a function, instead got a \'object\'')
+  }
+})
+
 test('should throw if the plugin is not a function', t => {
   t.plan(1)