Use required prettifier directly and tweak documentation

docs/pretty.md

@@ -3,12 +3,21 @@
 By default, Pino log lines are newline delimited JSON. This is perfect for
 production usage and long term storage. It's not so great for development
 environments. Thus, Pino logs can be prettified by using a Pino prettifier
-module.
+module like [`pino-pretty`][pp]:
 
-Pino prettifier modules are extra modules that provide [metadata streams][mdstreams].
-These modules provide a factory function which return a prettifier function.
-This prettifier function has an `asMetaWrapper(dest)` method attached to it.
-A psuedo-example is:
+```sh
+$ cat app.log | pino-pretty
+```
+
+## Prettifier API
+
+Pino prettifier modules are extra modules that provide a CLI for parsing ndJSON
+log lines piped via `stdin` and expose an API which conforms to the Pino
+[metadata streams](API.md#metadata) API.
+
+The API requires modules provide a factory function which return a prettifier
+function. This prettifier function has an `asMetaWrapper(dest)` method attached
+to it. A psuedo-example is:
 
 ```js
 module.exports = function myPrettifier (options) {
@@ -47,17 +56,19 @@ To use pretty printing in your project:
   const pino = require('pino')
   const log = pino({
     prettyPrint: {
-      prettifier: 'pino-pretty'
-    }
+      levelFirst: true
+    },
+    prettifier: require('pino-pretty')
   })
   ```
   Note: the default prettifier module is `pino-pretty`, so the preceeding
   example could be:
   ```js
-  const isdebug = require('isdebug') // true when NODE_ENV=development
   const pino = require('pino')
   const log = pino({
-    prettyPrint: isdebug
+    prettyPrint: {
+      levelFirst: true
+    }
   })
   ```
   See the [`pino-pretty` documentation][pp] for more information on the options

pino.js

@@ -272,14 +272,15 @@ Object.defineProperty(pinoPrototype, 'isLevelEnabled', {
   value: isLevelEnabled
 })
 
-function getPrettyStream (opts) {
-  var prettyFactory
-  var prettyModule = opts.prettifier || 'pino-pretty'
+function getPrettyStream (opts, prettifier) {
+  if (prettifier && typeof prettifier === 'function') {
+    return prettifier(opts).asMetaWrapper(process.stdout)
+  }
   try {
-    prettyFactory = require(prettyModule)
+    var prettyFactory = require('pino-pretty')
     return prettyFactory(opts).asMetaWrapper(process.stdout)
   } catch (e) {
-    throw Error(`Missing ${prettyModule} module: ${prettyModule} must be installed separately`)
+    throw Error('Missing `pino-pretty` module: `pino-pretty` must be installed separately')
   }
 }
 
@@ -297,7 +298,7 @@ function pino (opts, stream) {
   if (!isStdout && iopts.prettyPrint) throw Error('cannot enable pretty print when stream is not process.stdout')
   if (iopts.prettyPrint) {
     var prettyOpts = Object.assign({ messageKey: iopts.messageKey }, iopts.prettyPrint)
-    var pstream = getPrettyStream(prettyOpts)
+    var pstream = getPrettyStream(prettyOpts, iopts.prettifier)
     istream = pstream
   }
 

test/fixtures/pretty/prettyFactory.js

@@ -0,0 +1,6 @@
+global.process = { __proto__: process, pid: 123456 }
+Date.now = function () { return 1459875739796 }
+require('os').hostname = function () { return 'abcdefghijklmnopqr' }
+var pino = require(require.resolve('./../../../'))
+var log = pino({prettyPrint: {levelFirst: true}, prettifier: require('pino-pretty')})
+log.info('h')

test/pretty.test.js

@@ -36,6 +36,21 @@ test('can be enabled via constructor with pretty configuration', function (t) {
   })
 })
 
+test('can be enabled via constructor with prettifier', function (t) {
+  t.plan(1)
+  var actual = ''
+  var child = fork(path.join(__dirname, 'fixtures', 'pretty', 'prettyFactory.js'), {silent: true})
+
+  child.stdout.pipe(writeStream(function (s, enc, cb) {
+    actual += s
+    cb()
+  }))
+
+  child.on('close', function () {
+    t.notEqual(actual.match(/^INFO.*h/), null)
+  })
+})
+
 test('throws error when enabled with stream specified', function (t) {
   t.plan(1)
   var logStream = writeStream(function (s, enc, cb) {