stream: Don't emit 'end' unless read() called

This solves the problem of calling `readable.pipe(writable)` after the
readable stream has already emitted 'end', as often is the case when
writing simple HTTP proxies.

The spirit of streams2 is that things will work properly, even if you
don't set them up right away on the first tick.

This approach breaks down, however, because pipe()ing from an ended
readable will just do nothing.  No more data will ever arrive, and the
writable will hang open forever never being ended.

However, that does not solve the case of adding a `on('end')` listener
after the stream has received the EOF chunk, if it was the first chunk
received (and thus, length was 0, and 'end' got emitted).  So, with
this, we defer the 'end' event emission until the read() function is
called.

Also, in pipe(), if the source has emitted 'end' already, we call the
cleanup/onend function on nextTick.  Piping from an already-ended stream
is thus the same as piping from a stream that is in the process of
ending.

Updates many tests that were relying on 'end' coming immediately, even
though they never read() from the req.

Fix #4942

2 files changed, 31 insertions, 22 deletions

diff --git a/lib/_stream_readable.js b/lib/_stream_readable.js
index 41cf8e89cc..b09694c071 100644
--- a/lib/_stream_readable.js
+++ b/lib/_stream_readable.js
@@ -49,6 +49,12 @@ function ReadableState(options, stream) {
   this.endEmitted = false;
   this.reading = false;
 
+  // In streams that never have any data, and do push(null) right away,
+  // the consumer can miss the 'end' event if they do some I/O before
+  // consuming the stream.  So, we don't emit('end') until some reading
+  // happens.
+  this.calledRead = false;
+
   // a flag to be able to tell if the onwrite cb is called immediately,
   // or on a later tick.  We set this to true at first, becuase any
   // actions that shouldn't happen until "later" should generally also
@@ -218,6 +224,7 @@ function howMuchToRead(n, state) {
 // you can override either this method, or the async _read(n) below.
 Readable.prototype.read = function(n) {
   var state = this._readableState;
+  state.calledRead = true;
   var nOrig = n;
 
   if (typeof n !== 'number' || n > 0)
@@ -430,13 +437,15 @@ Readable.prototype.pipe = function(dest, pipeOpts) {
   }
   state.pipesCount += 1;
 
-  if ((!pipeOpts || pipeOpts.end !== false) &&
-      dest !== process.stdout &&
-      dest !== process.stderr) {
-    src.once('end', onend);
-  } else {
-    src.once('end', cleanup);
-  }
+  var doEnd = (!pipeOpts || pipeOpts.end !== false) &&
+              dest !== process.stdout &&
+              dest !== process.stderr;
+
+  var endFn = doEnd ? onend : cleanup;
+  if (state.endEmitted)
+    process.nextTick(endFn);
+  else
+    src.once('end', endFn);
 
   dest.on('unpipe', onunpipe);
   function onunpipe(readable) {
@@ -853,12 +862,12 @@ function endReadable(stream) {
   if (state.length > 0)
     throw new Error('endReadable called on non-empty stream');
 
-  if (state.endEmitted)
-    return;
-  state.ended = true;
-  state.endEmitted = true;
-  process.nextTick(function() {
-    stream.readable = false;
-    stream.emit('end');
-  });
+  if (!state.endEmitted && state.calledRead) {
+    state.ended = true;
+    state.endEmitted = true;
+    process.nextTick(function() {
+      stream.readable = false;
+      stream.emit('end');
+    });
+  }
 }
diff --git a/lib/http.js b/lib/http.js
index 0f7ea853c0..2bceaa0152 100644
--- a/lib/http.js
+++ b/lib/http.js
@@ -416,13 +416,13 @@ IncomingMessage.prototype._addHeaderLine = function(field, value) {
 // Call this instead of resume() if we want to just
 // dump all the data to /dev/null
 IncomingMessage.prototype._dump = function() {
-  if (this._dumped)
-    return;
-
-  this._dumped = true;
-  if (this.socket.parser) this.socket.parser.incoming = null;
-  this.push(null);
-  readStart(this.socket);
+  if (!this._dumped) {
+    this._dumped = true;
+    if (this.socket.parser) this.socket.parser.incoming = null;
+    this.push(null);
+    readStart(this.socket);
+    this.read();
+  }
 };