fix: Improve error message for hooks check (#4387)

* Improve error message for hooks check

* log null value more precisely

* final update and all testcase passed

lib/hooks.js

@@ -52,7 +52,7 @@ Hooks.prototype.validate = function (hook, fn) {
   if (supportedHooks.indexOf(hook) === -1) {
     throw new Error(`${hook} hook not supported!`)
   }
-  if (typeof fn !== 'function') throw new FST_ERR_HOOK_INVALID_HANDLER(hook, typeof fn)
+  if (typeof fn !== 'function') throw new FST_ERR_HOOK_INVALID_HANDLER(hook, Object.prototype.toString.call(fn))
 }
 
 Hooks.prototype.add = function (hook, fn) {

lib/route.js

@@ -249,11 +249,11 @@ function buildRouting (options) {
           if (Array.isArray(opts[hook])) {
             for (const func of opts[hook]) {
               if (typeof func !== 'function') {
-                throw new FST_ERR_HOOK_INVALID_HANDLER(hook, typeof func)
+                throw new FST_ERR_HOOK_INVALID_HANDLER(hook, Object.prototype.toString.call(func))
               }
             }
           } else if (opts[hook] !== undefined && typeof opts[hook] !== 'function') {
-            throw new FST_ERR_HOOK_INVALID_HANDLER(hook, typeof opts[hook])
+            throw new FST_ERR_HOOK_INVALID_HANDLER(hook, Object.prototype.toString.call(opts[hook]))
           }
         }
       }

test/hooks.test.js

@@ -3332,7 +3332,7 @@ test('registering invalid hooks should throw an error', async t => {
         return 'hello world'
       }
     })
-  }, new Error('onRequest hook should be a function, instead got undefined'))
+  }, new Error('onRequest hook should be a function, instead got [object Undefined]'))
 
   t.throws(() => {
     fastify.route({
@@ -3343,7 +3343,7 @@ test('registering invalid hooks should throw an error', async t => {
         return 'hello world'
       }
     })
-  }, new Error('onRequest hook should be a function, instead got object'))
+  }, new Error('onRequest hook should be a function, instead got [object Null]'))
 
   // undefined is ok
   fastify.route({
@@ -3363,5 +3363,5 @@ test('registering invalid hooks should throw an error', async t => {
     fastify.get('/', function (request, reply) {
       reply.send('hello world')
     })
-  }, new Error('onSend hook should be a function, instead got undefined'))
+  }, new Error('onSend hook should be a function, instead got [object Undefined]'))
 })

test/internals/hooks.test.js

@@ -78,6 +78,6 @@ test('should throw on wrong parameters', t => {
     t.fail()
   } catch (e) {
     t.equal(e.code, 'FST_ERR_HOOK_INVALID_HANDLER')
-    t.equal(e.message, 'onSend hook should be a function, instead got object')
+    t.equal(e.message, 'onSend hook should be a function, instead got [object Null]')
   }
 })