stream: always defer 'readable' with nextTick

Emit 'readable' always in the next tick, resulting in a single
call to _read() per microtick. This removes the need for the
user to implement buffering if they wanted to call this.push()
multiple times in an asynchronous fashion, as this.push() triggers
this._read() call.

PR-URL: https://github.com/nodejs/node/pull/17979
Fixes: https://github.com/nodejs/node/issues/3203
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Benjamin Gruenbaum <benjamingr@gmail.com>

1 files changed, 7 insertions, 6 deletions

diff --git a/test/parallel/test-stream2-transform.js b/test/parallel/test-stream2-transform.js
index d085926542..68c25141aa 100644
--- a/test/parallel/test-stream2-transform.js
+++ b/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, 1);
   assert.strictEqual(pt.read(5).toString(), 'l');
   assert.strictEqual(pt.read(5), null);
 
-  assert.strictEqual(emits, 3);
+  assert.strictEqual(emits, 1);
 }
 
 {
@@ -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();
     }));