From f9e1af95c2e91e76444f4f226846f4359fff38fd Mon Sep 17 00:00:00 2001
From: Basilisk-Dev <basiliskdev@protonmail.com>
Date: Fri, 8 May 2026 22:30:41 -0400
Subject: [PATCH] Fix readable stream transfer queueing

---
 js/src/builtin/Stream.cpp | 121 ++++++++++++++++++++++++++++++++++----
 1 file changed, 110 insertions(+), 11 deletions(-)

diff --git a/js/src/builtin/Stream.cpp b/js/src/builtin/Stream.cpp
index 7234ed596a..31f2238085 100644
--- a/js/src/builtin/Stream.cpp
+++ b/js/src/builtin/Stream.cpp
@@ -5058,7 +5058,15 @@ js::ByteLengthQueuingStrategy::constructor(JSContext* cx, unsigned argc, Value*
 {
     CallArgs args = CallArgsFromVp(argc, vp);
 
-    RootedObject strategy(cx, NewBuiltinClassInstance<ByteLengthQueuingStrategy>(cx));
+    if (!ThrowIfNotConstructing(cx, args, "ByteLengthQueuingStrategy"))
+        return false;
+
+    RootedObject proto(cx);
+    RootedObject newTarget(cx, &args.newTarget().toObject());
+    if (!GetPrototypeFromConstructor(cx, newTarget, &proto))
+        return false;
+
+    RootedObject strategy(cx, NewObjectWithClassProto<ByteLengthQueuingStrategy>(cx, proto));
     if (!strategy)
         return false;
 
@@ -5104,7 +5112,16 @@ js::CountQueuingStrategy::constructor(JSContext* cx, unsigned argc, Value* vp)
 {
     CallArgs args = CallArgsFromVp(argc, vp);
 
-    Rooted<CountQueuingStrategy*> strategy(cx, NewBuiltinClassInstance<CountQueuingStrategy>(cx));
+    if (!ThrowIfNotConstructing(cx, args, "CountQueuingStrategy"))
+        return false;
+
+    RootedObject proto(cx);
+    RootedObject newTarget(cx, &args.newTarget().toObject());
+    if (!GetPrototypeFromConstructor(cx, newTarget, &proto))
+        return false;
+
+    Rooted<CountQueuingStrategy*> strategy(cx);
+    strategy = NewObjectWithClassProto<CountQueuingStrategy>(cx, proto);
     if (!strategy)
         return false;
 
@@ -6808,25 +6825,107 @@ js::InitStreamExtras(JSContext* cx, HandleObject global)
     if (stream.locked)
       return null;
     try {
-      return { reader: stream.getReader() };
+      var record = {
+        reader: stream.getReader(),
+        pendingRead: undefined,
+        pumping: undefined,
+        closed: false,
+        errored: false,
+        canceled: false
+      };
+      ensureReadableTransferRead(record);
+      return record;
     } catch (e) {
       return null;
     }
   }
 
+  function ensureReadableTransferRead(record) {
+    if (!record.pendingRead && !record.closed && !record.errored &&
+        !record.canceled) {
+      try {
+        record.pendingRead = Promise.resolve(record.reader.read());
+      } catch (e) {
+        record.pendingRead = Promise.reject(e);
+      }
+      silenceRejection(record.pendingRead);
+    }
+    return record.pendingRead;
+  }
+
+  function errorReadableTransfer(record, controller, error) {
+    if (record.canceled || record.closed || record.errored)
+      return;
+    record.errored = true;
+    try { controller.error(error); } catch (e) {}
+  }
+
+  function pumpReadableTransfer(record, controller) {
+    if (record.pumping || record.closed || record.errored || record.canceled)
+      return;
+
+    var pendingRead = ensureReadableTransferRead(record);
+    if (!pendingRead)
+      return;
+
+    record.pumping = pendingRead.then(function(result) {
+      record.pendingRead = undefined;
+      record.pumping = undefined;
+
+      if (record.canceled || record.errored || record.closed)
+        return;
+
+      if (result.done) {
+        record.closed = true;
+        try { controller.close(); } catch (e) {}
+        return;
+      }
+
+      if (isUncloneableStreamChunk(result.value)) {
+        var cloneError = makeDataCloneError();
+        silenceRejection(record.reader.cancel(cloneError));
+        errorReadableTransfer(record, controller, cloneError);
+        return;
+      }
+
+      try {
+        controller.enqueue(result.value);
+      } catch (e) {
+        silenceRejection(record.reader.cancel(e));
+        errorReadableTransfer(record, controller, e);
+        return;
+      }
+
+      if (controller.desiredSize > 0)
+        pumpReadableTransfer(record, controller);
+    }, function(error) {
+      record.pendingRead = undefined;
+      record.pumping = undefined;
+      errorReadableTransfer(record, controller, error);
+    });
+    silenceRejection(record.pumping);
+  }
+
+  function cancelReadableTransfer(record, reason) {
+    record.canceled = true;
+    Promise.resolve().then(function() {
+      try {
+        silenceRejection(record.reader.cancel(reason));
+      } catch (e) {}
+    });
+    return undefined;
+  }
+
   function __uxpReceiveReadableStreamTransfer(record) {
     return new ReadableStream({
+      start: function(controller) {
+        pumpReadableTransfer(record, controller);
+      },
       pull: function(controller) {
-        return record.reader.read().then(function(result) {
-          if (result.done) {
-            controller.close();
-            return;
-          }
-          controller.enqueue(result.value);
-        });
+        pumpReadableTransfer(record, controller);
       },
       cancel: function(reason) {
-        return record.reader.cancel(reason);
+        return cancelReadableTransfer(record, reason);
       }
     });
   }