Support webpack (#97)

Fix #96

Author: mcollina

plugin.js

@@ -59,9 +59,18 @@ function checkVersion (version, pluginName) {
     throw new TypeError(`fastify-plugin expects a version string, instead got '${typeof version}'`)
   }
 
+  // TODO refactor this check and move it inside Fastify itself.
   var fastifyVersion
   try {
-    const pkgPath = join(dirname(require.resolve('fastify', { paths: [require.main.filename] })), 'package.json')
+    var pkgPath
+    if (require.main.filename) {
+      // We need to dynamically compute this to support yarn pnp
+      pkgPath = join(dirname(require.resolve('fastify', { paths: [require.main.filename] })), 'package.json')
+    } else {
+      // In bundlers, there is no require.main.filename so we go ahead and require directly
+      pkgPath = 'fastify/package.json'
+    }
+
     fastifyVersion = semver.coerce(require(pkgPath).version)
   } catch (_) {
     console.info('fastify not found, proceeding anyway')

test/bundlers.test.js

@@ -0,0 +1,27 @@
+'use strict'
+
+const { test } = require('tap')
+const fp = require('../plugin')
+
+test('webpack removes require.main.filename', (t) => {
+  const filename = require.main.filename
+  const info = console.info
+  t.tearDown(() => {
+    require.main.filename = filename
+    console.info = info
+  })
+
+  require.main.filename = null
+
+  console.info = function (msg) {
+    t.fail('logged: ' + msg)
+  }
+
+  fp((fastify, opts, next) => {
+    next()
+  }, {
+    fastify: '^3.0.0'
+  })
+
+  t.end()
+})