feat: add in i18n support for validator (#161)

* feat: add in i18n support for validator

Also includes the ability to customize error format

* fix: add tests to cover i18n and errorFormat

- revert how error was returned to pass tests
- lint code

* fix: pr change requests

* fix: remove errorFormat

* chore: lint and update tests

* Proposed alternative implementation that assumes you are using this in combination with the content-negotiation middleware

* Updated documentation

* version bump

README.md

@@ -602,7 +602,9 @@ Middy factory function. Use it to wrap your existing handler to enable middlewar
 
 ## middlewareFunction ⇒ <code>void</code> \| <code>Promise</code>
 **Kind**: global typedef  
-**Returns**: <code>void</code> \| <code>Promise</code> - - A middleware can return a Promise instead of using the `next` function as a callback.                         In this case middy will wait for the promise to resolve (or reject) and it will automatically                         propagate the result to the next middleware.  
+**Returns**: <code>void</code> \| <code>Promise</code> - - A middleware can return a Promise instead of using the `next` function as a callback.
+                         In this case middy will wait for the promise to resolve (or reject) and it will automatically
+                         propagate the result to the next middleware.  
 
 | Param | Type | Description |
 | --- | --- | --- |

docs/middlewares.md

@@ -439,7 +439,7 @@ handler
 
 Fetches parameters from [AWS Systems Manager Parameter Store](https://docs.aws.amazon.com/systems-manager/latest/userguide/systems-manager-paramstore.html).
 
-Parameters to fetch can be defined by path and by name (not mutually exclusive). See AWS docs [here](https://aws.amazon.com/blogs/mt/organize-parameters-by-hierarchy-tags-or-amazon-cloudwatch-events-with-amazon-ec2-systems-manager-parameter-store/). 
+Parameters to fetch can be defined by path and by name (not mutually exclusive). See AWS docs [here](https://aws.amazon.com/blogs/mt/organize-parameters-by-hierarchy-tags-or-amazon-cloudwatch-events-with-amazon-ec2-systems-manager-parameter-store/).
 
 By default parameters are assigned to the Node.js `process.env` object. They can instead be assigned to the function handler's `context` object by setting the `setToContext` flag to `true`. By default all parameters are added with uppercase names.
 
@@ -529,14 +529,16 @@ This middleware can be used in combination with
 [`httpErrorHandler`](#httperrorhandler) to automatically return the right
 response to the user.
 
+It can also be used in combination with [`httpcontentnegotiation`](#httpContentNegotiation) to load localised translations for the error messages (based on the currently requested language). This feature uses internally [`ajv-i18n`](http://npm.im/ajv-i18n) module, so reference to this module for options and more advanced use cases. By default the language used will be English (`en`), but you can redefine the default language by passing it in the `ajvOptions` options with the key `defaultLanguage` and specifying as value one of the [supported locales](https://www.npmjs.com/package/ajv-i18n#supported-locales).
+
 ### Options
 
  - `inputSchema` (object) (optional): The JSON schema object that will be used
    to validate the input (`handler.event`) of the Lambda handler.
  - `outputSchema` (object) (optional): The JSON schema object that will be used
    to validate the output (`handler.response`) of the Lambda handler.
  - `ajvOptions` (object) (optional): Options to pass to [ajv](https://epoberezkin.github.io/ajv/)
-    class constructor. Defaults are `{v5: true, $data: true, allErrors: true}`  
+    class constructor. Defaults are `{v5: true, coerceTypes: 'array', $data: true, allErrors: true, useDefaults: true, defaultLanguage: 'en'}`  
 
 ### Sample Usage
 

package.json

@@ -1,6 +1,6 @@
 {
   "name": "middy",
-  "version": "0.12.1",
+  "version": "0.13.0",
   "description": "🛵 The stylish Node.js middleware engine for AWS Lambda",
   "main": "./index.js",
   "files": [
@@ -67,6 +67,7 @@
     "@types/aws-lambda": "^8.10.1",
     "@types/http-errors": "^1.6.1",
     "ajv": "^6.0.0",
+    "ajv-i18n": "^3.1.0",
     "ajv-keywords": "^3.0.0",
     "content-type": "^1.0.4",
     "http-errors": "^1.6.2",

src/middlewares/__tests__/validator.js

@@ -59,6 +59,75 @@ describe('📦  Middleware Validator', () => {
     }
     handler(event, {}, (err, res) => {
       expect(err.message).toEqual('Event object failed validation')
+      expect(err.details).toEqual([{'dataPath': '', 'keyword': 'required', 'message': 'should have required property foo', 'params': {'missingProperty': 'foo'}, 'schemaPath': '#/required'}])
+    })
+  })
+
+  test('It should handle invalid schema as a BadRequest in a different language', () => {
+    const handler = middy((event, context, cb) => {
+      cb(null, event.body) // propagates the body as a response
+    })
+
+    const schema = {
+      required: ['body', 'foo'],
+      properties: {
+        // this will pass validation
+        body: {
+          type: 'string'
+        },
+        // this won't as it won't be in the event
+        foo: {
+          type: 'string'
+        }
+      }
+    }
+
+    handler.use(validator({
+      inputSchema: schema
+    }))
+
+    // invokes the handler, note that property foo is missing
+    const event = {
+      preferredLanguage: 'fr',
+      body: JSON.stringify({something: 'somethingelse'})
+    }
+    handler(event, {}, (err, res) => {
+      expect(err.message).toEqual('Event object failed validation')
+      expect(err.details).toEqual([{'dataPath': '', 'keyword': 'required', 'message': 'requiert la propriété foo', 'params': {'missingProperty': 'foo'}, 'schemaPath': '#/required'}])
+    })
+  })
+
+  test('It should handle invalid schema as a BadRequest in a different language (with normalization)', () => {
+    const handler = middy((event, context, cb) => {
+      cb(null, event.body) // propagates the body as a response
+    })
+
+    const schema = {
+      required: ['body', 'foo'],
+      properties: {
+        // this will pass validation
+        body: {
+          type: 'string'
+        },
+        // this won't as it won't be in the event
+        foo: {
+          type: 'string'
+        }
+      }
+    }
+
+    handler.use(validator({
+      inputSchema: schema
+    }))
+
+    // invokes the handler, note that property foo is missing
+    const event = {
+      preferredLanguage: 'pt',
+      body: JSON.stringify({something: 'somethingelse'})
+    }
+    handler(event, {}, (err, res) => {
+      expect(err.message).toEqual('Event object failed validation')
+      expect(err.details).toEqual([{'dataPath': '', 'keyword': 'required', 'message': 'deve ter a propriedade requerida foo', 'params': {'missingProperty': 'foo'}, 'schemaPath': '#/required'}])
     })
   })
 

src/middlewares/validator.js

@@ -1,13 +1,44 @@
 const createError = require('http-errors')
 const Ajv = require('ajv')
 const ajvKeywords = require('ajv-keywords')
-const {deepEqual} = require('assert')
+const ajvLocalize = require('ajv-i18n')
+const { deepEqual } = require('assert')
 
 let ajv
 let previousConstructorOptions
-const defaults = {v5: true, $data: true, allErrors: true}
+const defaults = {
+  v5: true,
+  coerceTypes: 'array', // important for query string params
+  allErrors: true,
+  useDefaults: true,
+  $data: true, // required for ajv-keywords
+  defaultLanguage: 'en'
+}
+
+const availableLanguages = Object.keys(ajvLocalize)
+
+/* in ajv-i18n Portuguese is represented as pt-BR */
+const languageNormalizationMap = {
+  'pt': 'pt-BR',
+  'pt-br': 'pt-BR',
+  'pt_BR': 'pt-BR',
+  'pt_br': 'pt-BR'
+}
+
+const normalizePreferredLanguage = (lang) => languageNormalizationMap[lang] || lang
 
-module.exports = ({inputSchema, outputSchema, ajvOptions}) => {
+const chooseLanguage = ({ preferredLanguage }, defaultLanguage) => {
+  if (preferredLanguage) {
+    const lang = normalizePreferredLanguage(preferredLanguage)
+    if (availableLanguages.includes(lang)) {
+      return lang
+    }
+  }
+
+  return defaultLanguage
+}
+
+module.exports = ({ inputSchema, outputSchema, ajvOptions }) => {
   const options = Object.assign({}, defaults, ajvOptions)
   lazyLoadAjv(options)
 
@@ -24,14 +55,18 @@ module.exports = ({inputSchema, outputSchema, ajvOptions}) => {
 
       if (!valid) {
         const error = new createError.BadRequest('Event object failed validation')
+        handler.event.headers = Object.assign({}, handler.event.headers)
+        const language = chooseLanguage(handler.event, options.defaultLanguage)
+        ajvLocalize[language](validateInput.errors)
+
         error.details = validateInput.errors
         throw error
       }
 
       return next()
     },
     after (handler, next) {
-      if (!outputSchema) {
+      if (!outputSchema || (!handler.response && handler.error)) {
         return next()
       }