stream: optimize webstreams pipeTo

MattiasBuelens · aduh95 · commit 0278461d8315 · 2026-03-10T20:20:07.000+01:00
PR-URL: #62079 Reviewed-By: James M Snell <jasnell@gmail.com> Reviewed-By: Matteo Collina <matteo.collina@gmail.com>
diff --git a/lib/internal/webstreams/readablestream.js b/lib/internal/webstreams/readablestream.js
@@ -1532,10 +1532,12 @@ function readableStreamPipeTo(
   }
 
   async function step() {
-    if (shuttingDown)
-      return true;
+    if (shuttingDown) return true;
 
-    await writer[kState].ready.promise;
+    if (dest[kState].backpressure) {
+      await writer[kState].ready.promise;
+      if (shuttingDown) return true;
+    }
 
     const controller = source[kState].controller;
 
@@ -1549,7 +1551,6 @@ function readableStreamPipeTo(
       while (controller[kState].queue.length > 0) {
         if (shuttingDown) return true;
 
-        source[kState].disturbed = true;
         const chunk = dequeueValue(controller);
 
         if (controller[kState].closeRequested && !controller[kState].queue.length) {
@@ -1563,20 +1564,17 @@ function readableStreamPipeTo(
         setPromiseHandled(state.currentWrite);
 
         // Check backpressure after each write
-        if (dest[kState].state === 'writable') {
-          const desiredSize = writer.desiredSize;
-          if (desiredSize !== null && desiredSize <= 0) {
-            // Backpressure - stop batch and wait for ready
-            break;
-          }
+        if (dest[kState].backpressure) {
+          // Backpressure - stop batch and wait for ready
+          break;
+        } else if (dest[kState].state !== 'writable' || writableStreamCloseQueuedOrInFlight(dest)) {
+          // Closing or erroring - stop batch and wait for shutdown
+          break;
         }
       }
 
       // Trigger pull if needed after batch
-      if (source[kState].state === 'readable' &&
-          !controller[kState].closeRequested) {
-        readableStreamDefaultControllerCallPullIfNeeded(controller);
-      }
+      readableStreamDefaultControllerCallPullIfNeeded(controller);
 
       // Check if stream closed during batch
       if (source[kState].state === 'closed') {
