Merge pull request #38 from jkyberneees/improve-error-handling

Improving error handling

Author: jkyberneees

README.md

@@ -39,6 +39,7 @@ const service = require('restana')({
 - `maxParamLength`: Defines the custom length for parameters in parametric (standard, regex and multi) routes. Default value: `100`
 - `defaultRoute`: Default route handler when no route match occurs. Default value: `((req, res) => res.send(404))`
 - `disableResponseEvent`: If `TRUE`, there won't be `response` events triggered on the `res` object. Default value: `FALSE`
+- `errorHandler`: Optional global error handler function. Default value: `(err, req, res) => res.send(err)`
 
 ```js
 // accessing service configuration
@@ -191,22 +192,19 @@ service.start()
 
 #### Error handling
 ```js
-service.use((req, res, next) => {
-  res.on('response', e => {
-    if (e.code >= 400) {
-      if (e.data && e.data.errClass) {
-        console.log(e.data.errClass + ': ' + e.data.message)
-      } else {
-        console.log('error response, but not triggered by an Error instance')
-      }
-    }
-  })
+const service = require('restana')({
+  errorHandler (err, req, res) {
+    console.log(`Something was wrong: ${err.message || err}`)
+    res.send(err)
+  }
+})
 
-  return next()
+service.get('/throw', (req, res) => {
+  throw new Error('Upps!')
 })
 ```
 
-Third party middlewares support:
+#### Third party middlewares support:
 > Almost all middlewares using the *function (req, res, next)* signature format should work, considering that no custom framework feature is used.
 
 Examples :

demos/error-handler.js

@@ -0,0 +1,12 @@
+const service = require('../index')({
+  errorHandler (err, req, res) {
+    console.log(`Unexpected error: ${err.message}`)
+    res.send(err)
+  }
+})
+
+service.get('/throw', (req, res) => {
+  throw new Error('Upps!')
+})
+
+service.start()

index.d.ts

@@ -57,6 +57,12 @@ declare namespace restana {
     next: (error?: unknown) => void
   ) => void | Promise<unknown>
 
+  type ErrorHandler<P extends Protocol> = (
+    err: Error,
+    req: Request<P>,
+    res: Response<P>,
+  ) => void | Promise<unknown>
+
   interface RegisterRoute<P extends Protocol> {
     (
       path: string,
@@ -104,7 +110,7 @@ declare namespace restana {
     middlewares: RequestHandler<P>[]
   }
 
-  interface Router {}
+  interface Router { }
 
   interface Options<P extends Protocol> {
     server?: Server<P>
@@ -115,6 +121,7 @@ declare namespace restana {
     maxParamLength?: number
     defaultRoute?: RequestHandler<P>
     disableResponseEvent?: boolean
+    errorHandler: ErrorHandler<P>
   }
 
   interface Service<P extends Protocol> {

index.js

@@ -60,13 +60,16 @@ module.exports = (options = {}) => {
   // global middlewares holder
   const middlewares = []
   // routes registration shortcut factory
-  const addRoute = (method) => (path, ...args) => {
-    routeRegister(app, method, path, args)
+  const addRoute = (methods) => (path, ...args) => {
+    routeRegister(app, methods, path, args)
 
     // supporting method chaining for routes registration
     return app
   }
 
+  // error handler
+  const errorHandler = options.errorHandler || ((err, req, res) => res.send(err))
+
   // the "restana" service interface
   const app = {
     /**
@@ -133,13 +136,13 @@ module.exports = (options = {}) => {
               ...middlewares.slice(0),
               {
                 context: {},
-                handler: handlerCall(handler, ctx) // -> Function
+                handler: handlerCall(handler, ctx, errorHandler) // -> Function
               }
-            ], req, res)()
+            ], req, res, errorHandler)()
           } else {
             // directly call the route handler only
             // NOTE: we do this to increase performance
-            handlerCall(handler, ctx)(req, res)
+            handlerCall(handler, ctx, errorHandler)(req, res)
           }
         })
       } else {
@@ -170,7 +173,7 @@ module.exports = (options = {}) => {
               router.lookup(req, res)
             }
           }
-        ], req, res)()
+        ], req, res, errorHandler)()
       } else {
         // directly call the request router
         // NOTE: we do this to increase performance

libs/middleware-chain.js

@@ -4,8 +4,9 @@
  * @param {Array} middlewares
  * @param {Object} req
  * @param {Object} res
+ * @param {Function} errorHandler
  */
-const next = (middlewares, req, res) => {
+const next = (middlewares, req, res, errorHandler) => {
   // retrieve next middleware from chain
   const middleware = middlewares.shift()
 
@@ -16,13 +17,13 @@ const next = (middlewares, req, res) => {
 
       try {
         // invoke each middleware
-        const result = middleware.handler.call(middleware.context, req, res, next(middlewares, req, res))
+        const result = middleware.handler.call(middleware.context, req, res, next(middlewares, req, res, errorHandler))
         if (result instanceof Promise) {
           // async support
-          result.catch(res.send)
+          result.catch(err => errorHandler(err, req, res))
         }
       } catch (err) {
-        res.send(err)
+        errorHandler(err, req, res)
       }
     } else if (!res.finished) {
       res.send(res.statusCode)

libs/route-handler-caller.js

@@ -3,19 +3,19 @@
  *
  * @param {Function} handler The request handler function
  * @param {Object} ctx The request handler invokation context instance
+ * @param {Function} errHandler The error handler function
  */
-module.exports = (handler, ctx) => (req, res) => {
+module.exports = (handler, ctx, errHandler) => async (req, res) => {
   try {
     const result = handler.call(ctx, req, res, ctx)
+    // async support
     if (result instanceof Promise) {
-      // async support
-      result.then(data => {
-        if (undefined !== data) {
-          return res.send(data)
-        }
-      }).catch(res.send)
+      const data = await result
+      if (undefined !== data) {
+        return res.send(data)
+      }
     }
   } catch (err) {
-    res.send(err)
+    errHandler(err, req, res)
   }
 }