nodejs
diff --git a/‎lib/internal/webstreams/writablestream.js‎
Lines changed: 12 additions & 21 deletions b/‎lib/internal/webstreams/writablestream.js‎
Lines changed: 12 additions & 21 deletions
@@ -757,13 +757,15 @@ function writableStreamClose(stream) {
   return promise;
 }
 
-function writableStreamUpdateBackpressure(stream, backpressure) {
-  const streamState = stream[kState];
-  assert(streamState.state === 'writable');
-  assert(!streamState.closeQueuedOrInFlight);
-  const {
-    writer,
-  } = streamState;
+// Callers invoke this only in the 'writable' state with no close queued or
+// in flight (the two conditions the spec's assertions check), so the
+// backpressure value is derived here from the desired size instead of being
+// computed and passed in by each caller.
+function writableStreamUpdateBackpressure(controller, streamState) {
+  const controllerState = controller[kState];
+  const backpressure =
+    controllerState.highWaterMark - controllerState.queueTotalSize <= 0;
+  const writer = streamState.writer;
   if (writer !== undefined && streamState.backpressure !== backpressure) {
     if (backpressure) {
       // The spec replaces [[readyPromise]] with a fresh pending promise;
@@ -1100,9 +1102,7 @@ function writableStreamDefaultControllerWrite(controller, chunk, chunkSize) {
   const streamState = stream[kState];
   if (!streamState.closeQueuedOrInFlight &&
       streamState.state === 'writable') {
-    writableStreamUpdateBackpressure(
-      stream,
-      writableStreamDefaultControllerGetBackpressure(controller));
+    writableStreamUpdateBackpressure(controller, streamState);
   }
   writableStreamDefaultControllerAdvanceQueueIfNeeded(controller);
 }
@@ -1128,9 +1128,7 @@ function writableStreamDefaultControllerProcessWrite(controller, chunk) {
       dequeueValue(controller);
       if (!streamState.closeQueuedOrInFlight &&
           state === 'writable') {
-        writableStreamUpdateBackpressure(
-          stream,
-          writableStreamDefaultControllerGetBackpressure(controller));
+        writableStreamUpdateBackpressure(controller, streamState);
       }
       writableStreamDefaultControllerAdvanceQueueIfNeeded(controller);
     };
@@ -1229,10 +1227,6 @@ function writableStreamDefaultControllerClearAlgorithms(controller) {
   controller[kState].sizeAlgorithm = undefined;
 }
 
-function writableStreamDefaultControllerGetBackpressure(controller) {
-  return writableStreamDefaultControllerGetDesiredSize(controller) <= 0;
-}
-
 function writableStreamDefaultControllerAdvanceQueueIfNeeded(controller) {
   const {
     queue,
@@ -1317,9 +1311,7 @@ function setupWritableStreamDefaultController(
   };
   stream[kState].controller = controller;
 
-  writableStreamUpdateBackpressure(
-    stream,
-    writableStreamDefaultControllerGetBackpressure(controller));
+  writableStreamUpdateBackpressure(controller, stream[kState]);
 
   const startResult = startAlgorithm();
 
@@ -1402,7 +1394,6 @@ module.exports = {
   writableStreamDefaultControllerError,
   writableStreamDefaultControllerClose,
   writableStreamDefaultControllerClearAlgorithms,
-  writableStreamDefaultControllerGetBackpressure,
   writableStreamDefaultControllerAdvanceQueueIfNeeded,
   setupWritableStreamDefaultControllerFromSink,
   setupWritableStreamDefaultController,