middy - npm Package Compare versions

Comparing version 0.6.0 to 0.6.1

package.json

 {
   "name": "middy",
-  "version": "0.6.0",
+  "version": "0.6.1",
   "description": "The simple (but cool 😎) middleware engine for AWS lambda in Node.js",
@@ -5,0 +5,0 @@ "main": "src/index.js",

README.md

@@ -233,2 +233,49 @@ <div align="center">
 
+### Interrupt middleware execution early
+
+Some middlewares might need to stop the whole execution flow and return a response immediately.
+
+If you want to do this you can invoke `handler.callback` in your middleware and return early without invoking `next`.
+
+**Note**: this will totally stop the execution of successive middlewares in any phase (`before` and `after`) and returns
+and early response (or an error) directly at the lambda level. If you middlewares that do specific task on every requests
+like output serialization or error handling, those won't be invoked in this case.
+
+In this example we can use this capability for building a sample caching middleware:
+
+```javascript
+
+// some function that calculates the cache id based on the current event
+const calculateCacheId = (event) => { /* ... */ }
+const storage = {}
+
+// middleware
+const cacheMiddleware = (options) => {
+  let cacheKey
+  return ({
+    before: (handler, next) => {
+      cacheKey = options.calculateCacheId(handler.event)
+      if (options.storage.hasOwnProperty(cacheKey)) {
+        // exits early and returns the value from the cache if it's already there
+        return handler.callback(null, options.storage[cacheKey])
+      }
+
+      return next()
+    },
+    after: (handler, next) => {
+      // stores the calculated response in the cache
+      options.storage[cacheKey] = handler.response
+      next()
+    }
+  })
+}
+
+// sample Usage
+const handler = middy((event, context, callback) => { /* ... */ })
+  .use(cacheMiddleware({
+    calculateCacheId, storage
+  }))
+```
+
+
 ### Handling errors
@@ -563,3 +610,3 @@
 | --- | --- | --- |
-| handler | <code>function</code> | the original handler function.   It will expose properties `event`, `context`, `response` and `error` that can   be used to interact with the middleware lifecycle |
+| handler | <code>function</code> | the original handler function.   It will expose properties `event`, `context`, `response`, `error` and `callback` that can   be used to interact with the middleware lifecycle |
 | next | [<code>middlewareNextFunction</code>](#middlewareNextFunction) | the callback to invoke to pass the control to the next middleware |
@@ -566,0 +613,0 @@

src/__tests__/middy.js

@@ -567,2 +567,27 @@ const middy = require('../middy')
   })
+
+  test('Middlewares can be stopped by calling the callback from the context', (endTest) => {
+    const beforeMiddleware = (handler, next) => {
+      // calling the handler.callback directly and not calling next()
+      return handler.callback(null, 'ending early')
+    }
+
+    const beforeMiddleware2 = jest.fn()
+    const originalHandler = jest.fn()
+    const afterMiddleware = jest.fn()
+
+    const handler = middy(originalHandler)
+      .before(beforeMiddleware)
+      .before(beforeMiddleware2)
+      .after(afterMiddleware)
+
+    handler({}, {}, (err, response) => {
+      expect(err).toBeNull()
+      expect(response).toEqual('ending early')
+      expect(beforeMiddleware2).not.toHaveBeenCalled()
+      expect(originalHandler).not.toHaveBeenCalled()
+      expect(afterMiddleware).not.toHaveBeenCalled()
+      endTest()
+    })
+  })
 })

src/middy.js

@@ -42,3 +42,3 @@ const isPromise = require('./isPromise')
  * @param {function} handler - the original handler function.
- *   It will expose properties `event`, `context`, `response` and `error` that can
+ *   It will expose properties `event`, `context`, `response`, `error` and `callback` that can
  *   be used to interact with the middleware lifecycle
@@ -146,2 +146,3 @@ * @param {middlewareNextFunction} next - the callback to invoke to pass the control to the next middleware
     instance.context = context
+    instance.callback = callback
     instance.response = null
@@ -148,0 +149,0 @@ instance.error = null

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Improved metrics

Total package byte prevSize

345652

increased by1.17%

Lines of code

8994

increased by0.25%

Number of lines in readme file

634

increased by8.01%

No dependency changes