remove app.use and fix middleware tests (#3506)

README.md

@@ -195,7 +195,6 @@ matters to you.
 * <a href="./docs/Routes.md"><code><b>Routes</b></code></a>
 * <a href="./docs/Encapsulation.md"><code><b>Encapsulation</b></code></a>
 * <a href="./docs/Logging.md"><code><b>Logging</b></code></a>
-* <a href="./docs/Middleware.md"><code><b>Middleware</b></code></a>
 * <a href="./docs/Hooks.md"><code><b>Hooks</b></code></a>
 * <a href="./docs/Decorators.md"><code><b>Decorators</b></code></a>
 * <a href="./docs/Validation-and-Serialization.md"><code><b>Validation and Serialization</b></code></a>

docs/Migration-Guide-V4.md

@@ -0,0 +1,12 @@
+# V4 Migration Guide
+
+This guide is intended to help with migration from Fastify v3 to v4.
+
+Before migrating to v4, please ensure that you have fixed all deprecation warningx from v3.
+All v3 deprecations have been removed and they will no longer work after upgrading.
+
+## Breaking Changes
+
+### Deprecation of `app.use()`
+
+Starting this version of Fastify, we have deprecated the use of `app.use()`. We have decided not to support the use of middlewares. Both [`middie`](https://github.com/fastify/middie) and [`fastify-express`](https://github.com/fastify/fastify-express) will still be there and maintained. Use Fastify's [hooks](./Hooks.md) instead.

fastify.js

@@ -48,7 +48,6 @@ const { defaultInitOptions } = getSecuredInitialConfig
 
 const {
   FST_ERR_BAD_URL,
-  FST_ERR_MISSING_MIDDLEWARE,
   AVVIO_ERRORS_MAP,
   appendStackTrace
 } = require('./lib/errors')
@@ -324,11 +323,6 @@ function fastify (options) {
     }
   })
 
-  // We are adding `use` to the fastify prototype so the user
-  // can still access it (and get the expected error), but `decorate`
-  // will not detect it, and allow the user to override it.
-  Object.setPrototypeOf(fastify, { use })
-
   if (options.schemaErrorFormatter) {
     validateSchemaErrorFormatter(options.schemaErrorFormatter)
     fastify[kSchemaErrorFormatter] = options.schemaErrorFormatter.bind(fastify)
@@ -493,10 +487,6 @@ function fastify (options) {
     }
   }
 
-  function use () {
-    throw new FST_ERR_MISSING_MIDDLEWARE()
-  }
-
   // Used exclusively in TypeScript contexts to enable auto type inference from JSON schema.
   function withTypeProvider () {
     return this

lib/errors.js

@@ -105,15 +105,6 @@ const codes = {
     "A callback for '%s' hook timed out. You may have forgotten to call 'done' function or to resolve a Promise"
   ),
 
-  /**
-   * Middlewares
-   */
-  FST_ERR_MISSING_MIDDLEWARE: createError(
-    'FST_ERR_MISSING_MIDDLEWARE',
-    'You must register a plugin for handling middlewares, visit fastify.io/docs/latest/Middleware/ for more info.',
-    500
-  ),
-
   /**
    * logger
   */

test/middleware.test.js

@@ -3,22 +3,9 @@
 const { test } = require('tap')
 const Fastify = require('..')
 const {
-  FST_ERR_DEC_ALREADY_PRESENT,
-  FST_ERR_MISSING_MIDDLEWARE
+  FST_ERR_DEC_ALREADY_PRESENT
 } = require('../lib/errors')
 
-test('Should throw if the basic use API has not been overridden', t => {
-  t.plan(1)
-  const fastify = Fastify()
-
-  try {
-    fastify.use()
-    t.fail('Should throw')
-  } catch (err) {
-    t.ok(err instanceof FST_ERR_MISSING_MIDDLEWARE)
-  }
-})
-
 test('Should be able to override the default use API', t => {
   t.plan(1)
   const fastify = Fastify()
@@ -38,7 +25,7 @@ test('Cannot decorate use twice', t => {
 })
 
 test('Encapsulation works', t => {
-  t.plan(2)
+  t.plan(1)
   const fastify = Fastify()
 
   fastify.register((instance, opts, done) => {
@@ -47,15 +34,5 @@ test('Encapsulation works', t => {
     done()
   })
 
-  fastify.register((instance, opts, done) => {
-    try {
-      instance.use()
-      t.fail('Should throw')
-    } catch (err) {
-      t.ok(err instanceof FST_ERR_MISSING_MIDDLEWARE)
-    }
-    done()
-  })
-
   fastify.ready()
 })