added async pipeline utility

index.js

@@ -16,6 +16,15 @@ function compose(middlewares) {
  }
 }
 
+exports.pipeline = pipeline
+function pipeline(funs) {
+ validateEach(isFunction, funs)
+ return async function asyncPipeline(value) {
+ for (const fun of funs) value = await fun(value)
+ return value
+ }
+}
+
 // Special-cased for nicer error messages.
 exports.toHandler = toHandler
 function toHandler(nextHandler, middleware) {
@@ -40,7 +49,7 @@ function toKoaMiddleware(middleware) {
 
 exports.toPlainResponse = toPlainResponse
 function toPlainResponse(response) {
- if (!isResponseDefined(response)) return null
+ if (!isResponseSettled(response)) return null
  const {status, headers, body} = response
  return {status, headers, body}
 }
@@ -73,6 +82,9 @@ function mount(path, middleware) {
  const handler = toHandler(next, middleware)
 
  return function mountedHandler(request) {
+ if (!isString(request.url)) {
+ throw Error(`Expected request URL to be a string, got: ${request.url}`)
+ }
  const urlSegments = splitPath(request.url)
 
  return testBy(segmentsTest, urlSegments)
@@ -105,7 +117,7 @@ async function runNextKoaMiddleware(request) {
  return null
 }
 
-function isResponseDefined({status, body}) {
+function isResponseSettled({status, body}) {
  return (isFinite(status) && status !== 404) || Boolean(body)
 }
 

package.json

@@ -1,6 +1,6 @@
 {
  "name": "koa-ring",
- "version": "0.0.4",
+ "version": "0.0.5",
  "description": "Write Koa middleware as ƒ(request) -> response, like in Clojure/Ring. Supports automatic work cancelation via Posterus futures and coroutines. Comes with routing/mounting utilities out of the box.",
  "license": "MIT",
  "keywords": [

posterus.js

@@ -1,9 +1,19 @@
 'use strict'
 
-const {isObject, isFunction, validate} = require('fpx')
+const {isObject, isFunction, validate, validateEach} = require('fpx')
 const {Future, isFuture} = require('posterus')
 const {routine} = require('posterus/routine')
-const {toHandler, toPlainResponse, updateKoaResponse, quietExtend} = require('./index')
+const index = require('./index')
+const {toHandler, toPlainResponse, updateKoaResponse, quietExtend} = index
+
+exports.pipeline = pipeline
+function pipeline(funs) {
+ validateEach(isFunction, funs)
+ return function* asyncPipeline(value) {
+ for (const fun of funs) value = yield fun(value)
+ return value
+ }
+}
 
 exports.toKoaMiddleware = toKoaMiddleware
 function toKoaMiddleware(middleware) {

readme.md

@@ -21,6 +21,7 @@ Includes support for basic routing and pattern-matching.
  * [Request](#request)
  * [Response](#response)
  * [`compose`](#compose)
+ * [`pipeline`](#pipeline)
  * [`toKoaMiddleware`](#tokoamiddleware)
  * [`mount`](#mount)
  * [`match`](#match)
@@ -280,6 +281,29 @@ const second = () => request => ({body: request.body})
 const middleware = compose([first, second])
 ```
 
+### `pipeline`
+
+Combines multiple async functions, such as request handlers, into one function
+that will invoke them left-to-right. Useful for composing request handlers with
+functions that transform request or response, without having to write those
+functions as middleware.
+
+```js
+const {pipeline, extend} = require('koa-ring')
+
+const transformRequest = async request => extend(request, {body: 'overwritten body'})
+
+const transformResponse => async response => extend(response, {status: 412})
+
+const middleware = next => pipeline([transformRequest, next, transformResponse])
+```
+
+Import the future-based version from `koa-ring/posterus`:
+
+```js
+const {pipeline} = require('koa-ring/posterus')
+```
+
 ### `toKoaMiddleware`
 
 Adapts a `koa-ring` middleware to be plugged into Koa. You should compose your
@@ -301,6 +325,12 @@ const echoMiddleware = () => echo
 app.use(toKoaMiddleware(echoMiddleware))
 ```
 
+Import the future-based version from `koa-ring/posterus`:
+
+```js
+const {toKoaMiddleware} = require('koa-ring/posterus')
+```
+
 ### `mount`
 
 Routing tool. Creates a middleware mounted on a subpath. The matched part is
@@ -352,13 +382,13 @@ const filtered = match({url: /^[/]?api[/]echo/, method: 'POST'}, middleware)
 
 See [motivation](#cancelation) for supporting futures.
 
-To use `koa-ring` with Posterus futures and coroutines, use `toKoaMiddleware`
-from the optional `koa-ring/posterus` module.
+To use `koa-ring` with Posterus futures and coroutines, some functions must be
+imported from the optional `koa-ring/posterus` module.
 
 ```js
 const Koa = require('koa')
-const {compose} = require('koa-ring')
-const {toKoaMiddleware} = require('koa-ring/posterus')
+const {compose, /* ... */} = require('koa-ring')
+const {toKoaMiddleware, pipeline} = require('koa-ring/posterus')
 
 const app = new Koa()