Fix passthrough streams

Author: kasperisager

index.js

@@ -186,6 +186,8 @@ exports.Transform = class Transform extends stream.Transform {
 
     if (this._transform !== stream.Transform.prototype._transform) {
       this._transform = transform.bind(this, this._transform)
+    } else {
+      this._transform = passthrough
     }
   }
 
@@ -271,6 +273,10 @@ function destroy (destroy, cb) {
   destroy.call(this, stream.getStreamError(this), cb)
 }
 
+function passthrough (data, cb) {
+  cb(null, data.chunk)
+}
+
 function byteLengthWritable (data) {
   return data.chunk.byteLength
 }

test.js

@@ -1,5 +1,5 @@
 const test = require('brittle')
-const { Readable, Writable, Duplex, Transform } = require('.')
+const { Readable, Writable, Duplex, Transform, PassThrough } = require('.')
 
 test('readable', (t) => {
   t.plan(3)
@@ -445,3 +445,29 @@ test('transform, write with encoding', (t) => {
 
   stream.write('\xab\xcd', 'ascii')
 })
+
+test('passthrough', (t) => {
+  t.plan(4)
+
+  const writable = new Writable({
+    write (data, encoding, cb) {
+      t.is(this, writable)
+      t.alike(data, Buffer.from('hello'))
+      t.is(encoding, 'buffer')
+    }
+  })
+
+  const readable = new Readable({
+    read (size) {
+      t.is(this, readable)
+
+      this.push('hello')
+      this.push(null)
+    }
+  })
+
+  const passthrough = new PassThrough()
+
+  readable.pipe(passthrough).pipe(writable)
+  readable.read()
+})