Merge pull request #3 from Kikobeats/piping

feat: add piping support

README.md

@@ -28,22 +28,22 @@ It's recommended to bind **tinyspawn** to `$`:
 const $ = require('tinyspawn')
 ```
 
-After that, pass the command (with arguments) to execute as first argument:
+After that, pass the command (with arguments) to be executed as first argument:
 
 ```js
 const { stdout } = await $(`node -e 'console.log("hello world")'`)
 console.log(stdout) // => 'hello world'
 ```
 
-Additionally, you can pass [spawn#options](https://nodejs.org/api/child_process.html#child_processspawncommand-args-options) as second argument:
+You can pass any [spawn#options](https://nodejs.org/api/child_process.html#child_processspawncommand-args-options) as second argument:
 
 ```js
 const { stdout } = $(`node -e 'console.log("hello world")'`, {
   shell: true
 })
 ```
 
-Any of the [ChildProcess](https://nodejs.org/api/child_process.html#class-childprocess) instance properties are available as part of the output:
+The output is a [ChildProcess](https://nodejs.org/api/child_process.html#class-childprocess) instance:
 
 ```js
 const {
@@ -60,6 +60,19 @@ const {
 } = await $('date')
 ```
 
+### Piping
+
+Since **tinyspawn** returns a [ChildProcess](https://nodejs.org/api/child_process.html#class-childprocess) instance, you can use it for interacting with other Node.js streams:
+
+```js
+// It's a childProcess instance
+const subprocess = $('echo 1234567890')
+subprocess.stdout.pipe(process.stdout) // => 1234567890
+
+// And it's a promise too
+await subprocess
+```
+
 ### JSON parsing
 
 **tinyspawn** has been designed to work with CLI commands that outputs json.

src/index.js

@@ -15,10 +15,12 @@ const parse = (stream, { json } = {}) => (encoding, start, end) => {
 
 const extend = defaults => (input, options) => {
   const [cmd, ...args] = input.split(' ').filter(Boolean)
+  let childProcess
 
-  return new Promise((resolve, reject) => {
+  const promise = new Promise((resolve, reject) => {
     const opts = { ...defaults, ...options }
-    const childProcess = spawn(cmd, args, opts)
+    childProcess = spawn(cmd, args, opts)
+
     const stdout = eos(childProcess, 'stdout')
     const stderr = eos(childProcess, 'stderr')
 
@@ -38,6 +40,8 @@ const extend = defaults => (input, options) => {
         reject(error)
       })
   })
+
+  return Object.assign(promise, childProcess)
 }
 
 const $ = extend()

test/index.js

@@ -1,5 +1,7 @@
 'use strict'
 
+const { Writable } = require('stream')
+const { EOL } = require('os')
 const test = require('ava')
 
 const $ = require('..').extend({ shell: true })
@@ -54,3 +56,22 @@ test('$.json', async t => {
   const { stdout } = await require('..').json('curl https://geolocation.microlink.io')
   t.true(!!stdout.ip.address)
 })
+
+test('piping subprocess', async t => {
+  const stream = new Writable({
+    construct (callback) {
+      this.buffer = []
+      callback()
+    },
+    write (chunk, encoding, callback) {
+      this.buffer.push(chunk)
+      callback()
+    }
+  })
+
+  const subprocess = $('echo 1234567890')
+  subprocess.stdout.pipe(stream)
+  await subprocess
+
+  t.is(stream.buffer.toString(), `1234567890${EOL}`)
+})