Fix 4204

lib/fourOhFour.js

@@ -10,7 +10,8 @@ const {
   kCanSetNotFoundHandler,
   kFourOhFourLevelInstance,
   kFourOhFourContext,
-  kHooks
+  kHooks,
+  kErrorHandler
 } = require('./symbols.js')
 const { lifecycleHooks } = require('./hooks')
 const { buildErrorHandler } = require('./error-handler.js')
@@ -148,6 +149,7 @@ function fourOhFour (options) {
           .map(h => h.bind(this))
         context[hook] = toSet.length ? toSet : null
       }
+      context.errorHandler = opts.errorHandler ? buildErrorHandler(this[kErrorHandler], opts.errorHandler) : this[kErrorHandler]
     })
 
     if (this[kFourOhFourContext] !== null && prefix === '/') {

test/404s.test.js

@@ -1944,3 +1944,68 @@ test('Send 404 when frameworkError calls reply.callNotFound', t => {
 
   t.end()
 })
+
+test('hooks are applied to not found handlers', async ({ equal }) => {
+  const fastify = Fastify()
+
+  // adding await here is fundamental for this test
+  await fastify.register(async function (fastify) {
+  })
+
+  fastify.setErrorHandler(function (_, request, reply) {
+    return reply.code(401).send({ error: 'Unauthorized' })
+  })
+
+  fastify.addHook('preValidation', async function (request, reply) {
+    throw new Error('kaboom')
+  })
+
+  const { statusCode } = await fastify.inject('/')
+  equal(statusCode, 401)
+})
+
+test('hooks are applied to not found handlers /2', async ({ equal }) => {
+  const fastify = Fastify()
+
+  async function plugin (fastify) {
+    fastify.setErrorHandler(function (_, request, reply) {
+      return reply.code(401).send({ error: 'Unauthorized' })
+    })
+  }
+
+  plugin[Symbol.for('skip-override')] = true
+
+  fastify.register(plugin)
+
+  fastify.addHook('preValidation', async function (request, reply) {
+    throw new Error('kaboom')
+  })
+
+  const { statusCode } = await fastify.inject('/')
+  equal(statusCode, 401)
+})
+
+test('hooks are applied to not found handlers /3', async ({ equal, fail }) => {
+  const fastify = Fastify()
+
+  async function plugin (fastify) {
+    fastify.setNotFoundHandler({ errorHandler }, async () => {
+      fail('this should never be called')
+    })
+
+    function errorHandler (_, request, reply) {
+      return reply.code(401).send({ error: 'Unauthorized' })
+    }
+  }
+
+  plugin[Symbol.for('skip-override')] = true
+
+  fastify.register(plugin)
+
+  fastify.addHook('preValidation', async function (request, reply) {
+    throw new Error('kaboom')
+  })
+
+  const { statusCode } = await fastify.inject('/')
+  equal(statusCode, 401)
+})