use internal labeled pipeline, fixes #15 (#20)

Transform order can be configured by setting `{ order: 'start' }` or
`{ order: 'end' }` in transform options.

Author: goto-bus-stop

index.js

@@ -1,4 +1,5 @@
 var parallel = require('async-collection').parallel
+var splicer = require('labeled-stream-splicer')
 var fromString = require('from2-string')
 var stream = require('readable-stream')
 var parse = require('fast-json-parse')
@@ -67,6 +68,9 @@ var placeholder = null
 Documentify.prototype.transform = function (transform, opts) {
   var self = this
   opts = opts || {}
+
+  if (!opts.order) opts = Object.assign({}, opts, { order: 'main' })
+
   if (typeof transform === 'string') {
     var index = this.transforms.length
     var basedir = opts.basedir || this.basedir
@@ -91,6 +95,24 @@ Documentify.prototype.transform = function (transform, opts) {
   return this
 }
 
+Documentify.prototype.createPipeline = function () {
+  var pipeline = splicer([
+    'start', [],
+    'main', [],
+    'end', []
+  ])
+
+  this.transforms.forEach(function (tuple) {
+    var fn = tuple[0]
+    var opts = tuple[1]
+    var label = opts && opts.order
+    var transform = fn(opts)
+    pipeline.get(label).push(transform)
+  })
+
+  return pipeline
+}
+
 Documentify.prototype.bundle = function () {
   var pts = new stream.PassThrough()
   var self = this
@@ -109,16 +131,9 @@ Documentify.prototype.bundle = function () {
     ]
     parallel(tasks, function (err) {
       if (err) return pts.emit('error', err)
-      var args = self.transforms.reduce(function (arr, tuple) {
-        var fn = tuple[0]
-        var opts = tuple[1] || {}
-        var transform = fn(opts)
-        arr.push(transform)
-        return arr
-      }, [source])
-
-      args.push(pts)
-      pump.apply(pump, args)
+      var pipeline = self.createPipeline()
+
+      pump(source, pipeline, pts)
     })
   }
 
@@ -159,6 +174,9 @@ Documentify.prototype.bundle = function () {
         opts = transform[1]
       }
 
+      // Run package.json transforms first by default.
+      if (!opts.order) opts.order = 'start'
+
       return function (done) {
         resolve(name, { basedir: basedir }, function (err, resolved) {
           if (err) return done(err)

package.json

@@ -16,6 +16,7 @@
     "findup": "^0.1.5",
     "from2-string": "^1.1.0",
     "inherits": "^2.0.3",
+    "labeled-stream-splicer": "^2.0.0",
     "pump": "^1.0.2",
     "readable-stream": "^2.3.3",
     "resolve": "^1.4.0",

test/order/transform.js

@@ -1,7 +1,13 @@
-var PassThrough = require('readable-stream').PassThrough
+var Transform = require('readable-stream').Transform
 
 module.exports = function () {
-  var ps = PassThrough()
-  ps.push('package.json prepend\n')
-  return ps
+  var first = true
+  return Transform({
+    transform (chunk, enc, cb) {
+      if (first) this.push('package.json prepend\n')
+      first = false
+      this.push(chunk)
+      cb(null)
+    }
+  })
 }

test/transforms.js

@@ -1,7 +1,6 @@
 var test = require('tape')
 var path = require('path')
 var Transform = require('readable-stream').Transform
-var PassThrough = require('readable-stream').PassThrough
 var concat = require('concat-stream')
 var documentify = require('../')
 
@@ -47,18 +46,24 @@ test('transforms', function (t) {
       .bundle()
       .pipe(concat({ encoding: 'string' }, function (result) {
         var lines = result.split(/\n/g)
-        t.equal(lines.shift(), '.transform prepend')
-        t.equal(lines.shift(), 'package.json prepend')
-        t.equal(lines.pop(), '.transform append')
-        t.equal(lines.pop(), 'package.json append')
+        t.equal(lines[0], '.transform prepend')
+        t.equal(lines[1], 'package.json prepend')
+        t.equal(lines[lines.length - 2], 'package.json append')
+        t.equal(lines[lines.length - 1], '.transform append')
       }))
   })
 })
 
 function prepend (text) {
-  var ps = PassThrough()
-  ps.push(text + '\n')
-  return ps
+  var first = true
+  return Transform({
+    write (chunk, enc, cb) {
+      if (first) this.push(text + '\n')
+      first = false
+      this.push(chunk)
+      cb()
+    }
+  })
 }
 function append (text) {
   return Transform({