stream: always defer 'readable' with nextTick

Fixes: #3203

Author: mcollina

lib/_stream_readable.js

@@ -508,16 +508,15 @@ function emitReadable(stream) {
   if (!state.emittedReadable) {
     debug('emitReadable', state.flowing);
     state.emittedReadable = true;
-    if (state.sync)
-      process.nextTick(emitReadable_, stream);
-    else
-      emitReadable_(stream);
+    process.nextTick(emitReadable_, stream);
   }
 }
 
 function emitReadable_(stream) {
+  var state = stream._readableState;
   debug('emit readable');
   stream.emit('readable');
+  state.needReadable = !state.flowing && !state.ended;
   flow(stream);
 }
 
@@ -644,6 +643,7 @@ Readable.prototype.pipe = function(dest, pipeOpts) {
     debug('ondata');
     increasedAwaitDrain = false;
     var ret = dest.write(chunk);
+    debug('dest.write', ret);
     if (false === ret && !increasedAwaitDrain) {
       // If the user unpiped during `dest.write()`, it is possible
       // to get stuck in a permanently paused state if that write
@@ -824,8 +824,8 @@ function resume(stream, state) {
 }
 
 function resume_(stream, state) {
+  debug('resume', state.reading);
   if (!state.reading) {
-    debug('resume read 0');
     stream.read(0);
   }
 

test/parallel/test-net-end-close.js

@@ -8,18 +8,22 @@ const uv = process.binding('uv');
 const s = new net.Socket({
   handle: {
     readStart: function() {
-      process.nextTick(() => this.onread(uv.UV_EOF, null));
+      setImmediate(() => this.onread(uv.UV_EOF, null));
     },
-    close: (cb) => process.nextTick(cb)
+    close: (cb) => setImmediate(cb)
   },
   writable: false
 });
 assert.strictEqual(s, s.resume());
 
 const events = [];
 
-s.on('end', () => events.push('end'));
-s.on('close', () => events.push('close'));
+s.on('end', () => {
+  events.push('end');
+});
+s.on('close', () => {
+  events.push('close');
+});
 
 process.on('exit', () => {
   assert.deepStrictEqual(events, [ 'end', 'close' ]);

test/parallel/test-stream-pipe-await-drain-push-while-write.js

@@ -3,32 +3,24 @@ const common = require('../common');
 const stream = require('stream');
 const assert = require('assert');
 
-const awaitDrainStates = [
-  1, // after first chunk before callback
-  1, // after second chunk before callback
-  0 // resolving chunk pushed after first chunk, awaitDrain is decreased
-];
-
-// A writable stream which pushes data onto the stream which pipes into it,
-// but only the first time it's written to. Since it's not paused at this time,
-// a second write will occur. If the pipe increases awaitDrain twice, we'll
-// never get subsequent chunks because 'drain' is only emitted once.
 const writable = new stream.Writable({
   write: common.mustCall(function(chunk, encoding, cb) {
-    if (chunk.length === 32 * 1024) { // first chunk
-      const beforePush = readable._readableState.awaitDrain;
-      readable.push(Buffer.alloc(34 * 1024)); // above hwm
-      // We should check if awaitDrain counter is increased.
-      const afterPush = readable._readableState.awaitDrain;
-      assert.strictEqual(afterPush - beforePush, 1,
-                         'Counter is not increased for awaitDrain');
-    }
-
     assert.strictEqual(
-      awaitDrainStates.shift(),
       readable._readableState.awaitDrain,
+      0,
       'State variable awaitDrain is not correct.'
     );
+
+    if (chunk.length === 32 * 1024) { // first chunk
+      readable.push(Buffer.alloc(34 * 1024)); // above hwm
+      // We should check if awaitDrain counter is increased in the next
+      // tick, because awaitDrain is incremented after this method finished
+      process.nextTick(() => {
+        assert.strictEqual(readable._readableState.awaitDrain, 1,
+                           'Counter is not increased for awaitDrain');
+      });
+    }
+
     cb();
   }, 3)
 });

test/parallel/test-stream-readable-emittedReadable.js

@@ -10,30 +10,33 @@ const readable = new Readable({
 // Initialized to false.
 assert.strictEqual(readable._readableState.emittedReadable, false);
 
+const expected = [Buffer.from('foobar'), Buffer.from('quo'), null];
 readable.on('readable', common.mustCall(() => {
   // emittedReadable should be true when the readable event is emitted
   assert.strictEqual(readable._readableState.emittedReadable, true);
-  readable.read();
+  assert.deepStrictEqual(readable.read(), expected.shift());
   // emittedReadable is reset to false during read()
   assert.strictEqual(readable._readableState.emittedReadable, false);
-}, 4));
+}, 3));
 
 // When the first readable listener is just attached,
 // emittedReadable should be false
 assert.strictEqual(readable._readableState.emittedReadable, false);
 
-// Each one of these should trigger a readable event.
+// These trigger a single 'readable', as things are batched up
 process.nextTick(common.mustCall(() => {
   readable.push('foo');
 }));
 process.nextTick(common.mustCall(() => {
   readable.push('bar');
 }));
-process.nextTick(common.mustCall(() => {
+
+// these triggers two readable events
+setImmediate(common.mustCall(() => {
   readable.push('quo');
-}));
-process.nextTick(common.mustCall(() => {
-  readable.push(null);
+  process.nextTick(common.mustCall(() => {
+    readable.push(null);
+  }));
 }));
 
 const noRead = new Readable({

test/parallel/test-stream-readable-needReadable.js

@@ -38,16 +38,17 @@ asyncReadable.on('readable', common.mustCall(() => {
     // then we need to notify the reader on future changes.
     assert.strictEqual(asyncReadable._readableState.needReadable, true);
   }
-}, 3));
+}, 2));
 
 process.nextTick(common.mustCall(() => {
   asyncReadable.push('foooo');
 }));
 process.nextTick(common.mustCall(() => {
   asyncReadable.push('bar');
 }));
-process.nextTick(common.mustCall(() => {
+setImmediate(common.mustCall(() => {
   asyncReadable.push(null);
+  assert.strictEqual(asyncReadable._readableState.needReadable, false);
 }));
 
 const flowing = new Readable({
@@ -84,13 +85,13 @@ slowProducer.on('readable', common.mustCall(() => {
 
 process.nextTick(common.mustCall(() => {
   slowProducer.push('foo');
-}));
-process.nextTick(common.mustCall(() => {
-  slowProducer.push('foo');
-}));
-process.nextTick(common.mustCall(() => {
-  slowProducer.push('foo');
-}));
-process.nextTick(common.mustCall(() => {
-  slowProducer.push(null);
+  process.nextTick(common.mustCall(() => {
+    slowProducer.push('foo');
+    process.nextTick(common.mustCall(() => {
+      slowProducer.push('foo');
+      process.nextTick(common.mustCall(() => {
+        slowProducer.push(null);
+      }));
+    }));
+  }));
 }));

test/parallel/test-stream-readable-object-multi-push-async.js

@@ -0,0 +1,56 @@
+'use strict';
+
+const common = require('../common');
+const assert = require('assert');
+const { Readable } = require('stream');
+
+const MAX = 42;
+const BATCH = 10;
+
+const readable = new Readable({
+  objectMode: true,
+  read: common.mustCall(function() {
+    console.log('>> READ');
+    fetchData((err, data) => {
+      if (err) {
+        this.destroy(err);
+        return;
+      }
+
+      if (data.length === 0) {
+        console.log('pushing null');
+        this.push(null);
+        return;
+      }
+
+      console.log('pushing');
+      data.forEach((d) => this.push(d));
+    });
+  }, Math.floor(MAX / BATCH) + 2)
+});
+
+let i = 0;
+function fetchData(cb) {
+  if (i > MAX) {
+    setTimeout(cb, 10, null, []);
+  } else {
+    const array = [];
+    const max = i + BATCH;
+    for (; i < max; i++) {
+      array.push(i);
+    }
+    setTimeout(cb, 10, null, array);
+  }
+}
+
+readable.on('readable', () => {
+  let data;
+  console.log('readable emitted');
+  while (data = readable.read()) {
+    console.log(data);
+  }
+});
+
+readable.on('end', () => {
+  assert.strictEqual(i, (Math.floor(MAX / BATCH) + 1) * BATCH);
+});

test/parallel/test-stream-readable-reading-readingMore.js

@@ -29,15 +29,19 @@ function onStreamEnd() {
   assert.strictEqual(state.reading, false);
 }
 
+const expected = [
+  true, // stream is not ended
+  false // stream is ended
+];
+
 readable.on('readable', common.mustCall(() => {
-  // 'readable' always gets called before 'end'
-  // since 'end' hasn't been emitted, more data could be incoming
-  assert.strictEqual(state.readingMore, true);
+  assert.strictEqual(state.readingMore, expected.shift());
 
   // if the stream has ended, we shouldn't be reading
   assert.strictEqual(state.ended, !state.reading);
 
-  if (readable.read() === null) // reached end of stream
+  const data = readable.read();
+  if (data === null) // reached end of stream
     process.nextTick(common.mustCall(onStreamEnd, 1));
 }, 2));
 

test/parallel/test-stream2-transform.js

@@ -306,25 +306,26 @@ const Transform = require('_stream_transform');
   pt.write(Buffer.from('foog'));
   pt.write(Buffer.from('bark'));
 
-  assert.strictEqual(emits, 1);
+  assert.strictEqual(emits, 0);
   assert.strictEqual(pt.read(5).toString(), 'foogb');
   assert.strictEqual(String(pt.read(5)), 'null');
+  assert.strictEqual(emits, 0);
 
   pt.write(Buffer.from('bazy'));
   pt.write(Buffer.from('kuel'));
 
-  assert.strictEqual(emits, 2);
+  assert.strictEqual(emits, 0);
   assert.strictEqual(pt.read(5).toString(), 'arkba');
   assert.strictEqual(pt.read(5).toString(), 'zykue');
   assert.strictEqual(pt.read(5), null);
 
   pt.end();
 
-  assert.strictEqual(emits, 3);
+  assert.strictEqual(emits, 0);
   assert.strictEqual(pt.read(5).toString(), 'l');
   assert.strictEqual(pt.read(5), null);
 
-  assert.strictEqual(emits, 3);
+  assert.strictEqual(emits, 0);
 }
 
 {
@@ -338,7 +339,7 @@ const Transform = require('_stream_transform');
   pt.write(Buffer.from('foog'));
   pt.write(Buffer.from('bark'));
 
-  assert.strictEqual(emits, 1);
+  assert.strictEqual(emits, 0);
   assert.strictEqual(pt.read(5).toString(), 'foogb');
   assert.strictEqual(pt.read(5), null);
 
@@ -352,7 +353,7 @@ const Transform = require('_stream_transform');
       pt.once('readable', common.mustCall(function() {
         assert.strictEqual(pt.read(5).toString(), 'l');
         assert.strictEqual(pt.read(5), null);
-        assert.strictEqual(emits, 4);
+        assert.strictEqual(emits, 3);
       }));
       pt.end();
     }));