stream: avoid unnecessary drain for sync stream

PR-URL: #50014

lib/internal/streams/transform.js

@@ -182,7 +182,12 @@ Transform.prototype._write = function(chunk, encoding, callback) {
       this.push(val);
     }
 
-    if (
+    if (rState.ended) {
+      // If user has called this.push(null) we have to
+      // delay the callback to properly progate the new
+      // state.
+      process.nextTick(callback);
+    } else if (
       wState.ended || // Backwards compat.
       length === rState.length || // Backwards compat.
       rState.length < rState.highWaterMark

lib/internal/streams/writable.js

@@ -108,6 +108,7 @@ const kWriteCb = 1 << 26;
 const kExpectWriteCb = 1 << 27;
 const kAfterWriteTickInfo = 1 << 28;
 const kAfterWritePending = 1 << 29;
+const kIsDuplex = 1 << 30;
 
 // TODO(benjamingr) it is likely slower to do it this way than with free functions
 function makeBitMapDescriptor(bit) {
@@ -286,6 +287,7 @@ function WritableState(options, stream, isDuplex) {
 
   if (options && options.objectMode) this.state |= kObjectMode;
   if (isDuplex && options && options.writableObjectMode) this.state |= kObjectMode;
+  if (isDuplex) this.state |= kIsDuplex;
 
   // The point at which write() starts returning false
   // Note: 0 is a valid value, means that we always return false if
@@ -513,14 +515,6 @@ function writeOrBuffer(stream, state, chunk, encoding, callback) {
 
   state.length += len;
 
-  // stream._write resets state.length
-  const ret = state.length < state.highWaterMark;
-
-  // We must ensure that previous needDrain will not be reset to false.
-  if (!ret) {
-    state.state |= kNeedDrain;
-  }
-
   if ((state.state & (kWriting | kErrored | kCorked | kConstructed)) !== kConstructed) {
     state.buffered.push({ chunk, encoding, callback });
     if ((state.state & kAllBuffers) !== 0 && encoding !== 'buffer') {
@@ -539,6 +533,12 @@ function writeOrBuffer(stream, state, chunk, encoding, callback) {
     state.state &= ~kSync;
   }
 
+  const ret = state.length < state.highWaterMark;
+
+  if (!ret) {
+    state.state |= kNeedDrain;
+  }
+
   // Return false if errored or destroyed in order to break
   // any synchronous while(stream.write(data)) loops.
   return ret && (state.state & (kDestroyed | kErrored)) === 0;