Write after end fix (#97)

* add failing test

* fix write-after-end edgecase

Author: mafintosh

index.js

@@ -71,7 +71,7 @@ const WRITE_CORKED     = 0b10000000000 << 18
 
 const WRITE_NOT_ACTIVE    = MAX ^ (WRITE_ACTIVE | WRITE_WRITING)
 const WRITE_NON_PRIMARY   = MAX ^ WRITE_PRIMARY
-const WRITE_NOT_FINISHING = MAX ^ WRITE_FINISHING
+const WRITE_NOT_FINISHING = MAX ^ (WRITE_ACTIVE | WRITE_FINISHING)
 const WRITE_DRAINED       = MAX ^ WRITE_UNDRAINED
 const WRITE_NOT_QUEUED    = MAX ^ WRITE_QUEUED
 const WRITE_NOT_NEXT_TICK = MAX ^ WRITE_NEXT_TICK
@@ -110,6 +110,7 @@ const WRITE_ACTIVE_AND_WRITING = WRITE_ACTIVE | WRITE_WRITING
 const WRITE_FINISHING_STATUS = OPEN_STATUS | WRITE_FINISHING | WRITE_QUEUED_AND_ACTIVE | WRITE_DONE
 const WRITE_BACKPRESSURE_STATUS = WRITE_UNDRAINED | DESTROY_STATUS | WRITE_FINISHING | WRITE_DONE
 const WRITE_UPDATE_SYNC_STATUS = WRITE_UPDATING | OPEN_STATUS | WRITE_NEXT_TICK | WRITE_PRIMARY
+const WRITE_DROP_DATA = WRITE_FINISHING | WRITE_DONE | DESTROY_STATUS
 
 const asyncIterator = Symbol.asyncIterator || Symbol('asyncIterator')
 
@@ -133,6 +134,7 @@ class WritableState {
   }
 
   push (data) {
+    if ((this.stream._duplexState & WRITE_DROP_DATA) !== 0) return false
     if (this.map !== null) data = this.map(data)
 
     this.buffered += this.byteLength(data)
@@ -197,7 +199,7 @@ class WritableState {
     const stream = this.stream
 
     if ((stream._duplexState & WRITE_FINISHING_STATUS) === WRITE_FINISHING) {
-      stream._duplexState = (stream._duplexState | WRITE_ACTIVE) & WRITE_NOT_FINISHING
+      stream._duplexState = stream._duplexState | WRITE_ACTIVE
       stream._final(afterFinal.bind(this))
       return
     }
@@ -489,7 +491,7 @@ function afterFinal (err) {
     stream._duplexState |= DESTROYING
   }
 
-  stream._duplexState &= WRITE_NOT_ACTIVE
+  stream._duplexState &= WRITE_NOT_FINISHING
 
   // no need to wait the extra tick here, so we short circuit that
   if ((stream._duplexState & WRITE_UPDATING) === 0) this.update()

test/duplex.js

@@ -60,3 +60,26 @@ test('wait for readable', function (t) {
     t.is(d.read(), 'ok')
   })
 })
+
+test('write during end', function (t) {
+  t.plan(3)
+
+  const expected = ['a', 'b']
+
+  const w = new Duplex({
+    write (data, cb) {
+      t.is(data, expected.shift())
+      cb(null)
+    },
+    final (cb) {
+      w.write('bad')
+      cb(null)
+    }
+  })
+
+  w.write('a')
+  w.write('b')
+  w.end()
+  w.on('finish', () => w.push(null))
+  w.on('close', () => t.pass('closed'))
+})