Pass in ajv instance

README.md

@@ -93,6 +93,23 @@ await fastify.register(responseValidator, {
 })
 ```
 
+You can also pass in an instance of ajv
+```js
+// Default configuration:
+//    coerceTypes: false
+//    useDefaults: true
+//    removeAdditional: true
+//    allErrors: true
+
+import responseValidator from '@fastify/response-validation'
+import Ajv from 'ajv'
+
+// ... App setup
+
+const ajv = new Ajv()
+await fastify.register(responseValidator, { ajv })
+```
+
 By default the response validation is enabled on every route that has a response schema defined. If needed you can disable it all together with `responseValidation: false`:
 ```js
 import responseValidator from '@fastify/response-validation'

index.js

@@ -4,26 +4,30 @@ const fp = require('fastify-plugin')
 const Ajv = require('ajv')
 
 function fastifyResponseValidation (fastify, opts, next) {
-  const { plugins: ajvPlugins, ...ajvOptions } = Object.assign({
-    coerceTypes: false,
-    useDefaults: true,
-    removeAdditional: true,
-    allErrors: true,
-    plugins: []
-  }, opts.ajv)
-
-  if (!Array.isArray(ajvPlugins)) {
-    next(new Error(`ajv.plugins option should be an array, instead got '${typeof ajvPlugins}'`))
-    return
-  }
-
-  const ajv = new Ajv(ajvOptions)
+  let ajv
+  if (opts.ajv && opts.ajv instanceof Ajv) {
+    ajv = opts.ajv
+  } else {
+    const { plugins: ajvPlugins, ...ajvOptions } = Object.assign({
+      coerceTypes: false,
+      useDefaults: true,
+      removeAdditional: true,
+      allErrors: true,
+      plugins: []
+    }, opts.ajv)
+
+    if (!Array.isArray(ajvPlugins)) {
+      next(new Error(`ajv.plugins option should be an array, instead got '${typeof ajvPlugins}'`))
+      return
+    }
+    ajv = new Ajv(ajvOptions)
 
-  for (const plugin of ajvPlugins) {
-    if (Array.isArray(plugin)) {
-      plugin[0](ajv, plugin[1])
-    } else {
-      plugin(ajv)
+    for (const plugin of ajvPlugins) {
+      if (Array.isArray(plugin)) {
+        plugin[0](ajv, plugin[1])
+      } else {
+        plugin(ajv)
+      }
     }
   }
 

test/ajv.test.js

@@ -3,6 +3,9 @@
 const test = require('tap').test
 const Fastify = require('fastify')
 const plugin = require('..')
+const Ajv = require('ajv')
+const ajvFormats = require('ajv-formats')
+const ajvErrors = require('ajv-errors')
 
 test('use ajv formats', async t => {
   const fastify = Fastify()
@@ -98,3 +101,78 @@ test('should throw an error if ajv.plugins is number', async t => {
   const fastify = Fastify()
   t.rejects(fastify.register(plugin, { ajv: { plugins: 0 } }), 'ajv.plugins option should be an array, instead got \'number\'')
 })
+
+test('use ajv formats with Ajv instance', async t => {
+  const fastify = Fastify()
+  const ajv = new Ajv()
+  ajvFormats(ajv)
+  await fastify.register(plugin, { ajv })
+
+  fastify.route({
+    method: 'GET',
+    url: '/',
+    schema: {
+      response: {
+        '2xx': {
+          type: 'object',
+          properties: {
+            answer: { type: 'number', format: 'float' }
+          }
+        }
+      }
+    },
+    handler: async (req, reply) => {
+      return { answer: 2.4 }
+    }
+  })
+
+  const response = await fastify.inject({
+    method: 'GET',
+    url: '/'
+  })
+
+  t.equal(response.statusCode, 200)
+  t.strictSame(JSON.parse(response.payload), { answer: 2.4 })
+})
+
+test('use ajv errors with Ajv instance', async t => {
+  const fastify = Fastify()
+  const ajv = new Ajv({ allErrors: true })
+  ajvErrors(ajv, { singleError: true })
+  await fastify.register(plugin, { ajv })
+
+  fastify.route({
+    method: 'GET',
+    url: '/',
+    schema: {
+      response: {
+        '2xx': {
+          type: 'object',
+          required: ['answer'],
+          properties: {
+            answer: { type: 'number' }
+          },
+          additionalProperties: false,
+          errorMessage: 'should be an object with an integer property answer only'
+        }
+      }
+    },
+    handler: async (req, reply) => {
+      return { notAnAnswer: 24 }
+    }
+  })
+
+  const response = await fastify.inject({
+    method: 'GET',
+    url: '/'
+  })
+
+  t.equal(response.statusCode, 500)
+  t.equal(response.json().message, 'response should be an object with an integer property answer only')
+})
+
+test('should throw an error if ajv.plugins is not passed to instance and not array', async t => {
+  t.plan(1)
+  const fastify = Fastify()
+  t.rejects(fastify.register(plugin, { ajv: { plugins: 'invalid' } }), 'ajv.plugins option should be an array, instead got \'string\'')
+})