Fix tee() incorrectly closing before enqueuing to the second branch

Author: MattiasBuelens

index.bs

@@ -2241,6 +2241,7 @@ create them does not matter.
  1. Assert: |cloneForBranch2| is a boolean.
  1. Let |reader| be ? [$AcquireReadableStreamDefaultReader$](|stream|).
  1. Let |reading| be false.
+ 1. Let |readAgain| be false.
  1. Let |canceled1| be false.
  1. Let |canceled2| be false.
  1. Let |reason1| be undefined.
@@ -2249,13 +2250,15 @@ create them does not matter.
  1. Let |branch2| be undefined.
  1. Let |cancelPromise| be [=a new promise=].
  1. Let |pullAlgorithm| be the following steps:
-  1. If |reading| is true, return [=a promise resolved with=] undefined.
+  1. If |reading| is true,
+   1. Set |readAgain| to true.
+   1. Return [=a promise resolved with=] undefined.
   1. Set |reading| to true.
   1. Let |readRequest| be a [=read request=] with the following [=struct/items=]:
    : [=read request/chunk steps=], given |chunk|
    ::
     1. [=Queue a microtask=] to perform the following steps:
-     1. Set |reading| to false.
+     1. Set |readAgain| to false.
      1. Let |chunk1| and |chunk2| be |chunk|.
      1. If |canceled2| is false and |cloneForBranch2| is true,
       1. Let |cloneResult| be [$StructuredClone$](|chunk2|).
@@ -2271,6 +2274,8 @@ create them does not matter.
      1. If |canceled2| is false, perform !
         [$ReadableStreamDefaultControllerEnqueue$](|branch2|.[=ReadableStream/[[controller]]=],
         |chunk2|).
+     1. Set |reading| to false.
+     1. If |readAgain| is true, perform |pullAlgorithm|.
 
     <p class="note">The microtask delay here is necessary because it takes at least a microtask to
     detect errors, when we use |reader|.[=ReadableStreamGenericReader/[[closedPromise]]=] below.
@@ -2331,6 +2336,8 @@ create them does not matter.
     {{ReadableByteStreamController}}.
  1. Let |reader| be ? [$AcquireReadableStreamDefaultReader$](|stream|).
  1. Let |reading| be false.
+ 1. Let |readAgainForBranch1| be false.
+ 1. Let |readAgainForBranch2| be false.
  1. Let |canceled1| be false.
  1. Let |canceled2| be false.
  1. Let |reason1| be undefined.
@@ -2357,7 +2364,8 @@ create them does not matter.
    : [=read request/chunk steps=], given |chunk|
    ::
     1. [=Queue a microtask=] to perform the following steps:
-     1. Set |reading| to false.
+     1. Set |readAgainForBranch1| to false.
+     1. Set |readAgainForBranch2| to false.
      1. Let |chunk1| and |chunk2| be |chunk|.
      1. If |canceled1| is false and |canceled2| is false,
       1. Let |cloneResult| be [$CloneAsUint8Array$](|chunk|).
@@ -2373,6 +2381,9 @@ create them does not matter.
      1. If |canceled2| is false, perform !
         [$ReadableByteStreamControllerEnqueue$](|branch2|.[=ReadableStream/[[controller]]=],
         |chunk2|).
+     1. Set |reading| to false.
+     1. If |readAgainForBranch1| is true, perform |pull1Algorithm|.
+     1. Otherwise, if |readAgainForBranch2| is true, perform |pull2Algorithm|.
 
     <p class="note">The microtask delay here is necessary because it takes at least a microtask to
     detect errors, when we use |reader|.[=ReadableStreamGenericReader/[[closedPromise]]=] below.
@@ -2410,7 +2421,8 @@ create them does not matter.
    : [=read-into request/chunk steps=], given |chunk|
    ::
     1. [=Queue a microtask=] to perform the following steps:
-     1. Set |reading| to false.
+     1. Set |readAgainForBranch1| to false.
+     1. Set |readAgainForBranch2| to false.
      1. Let |byobCanceled| be |canceled2| if |forBranch2| is true, and |canceled1| otherwise.
      1. Let |otherCanceled| be |canceled2| if |forBranch2| is false, and |canceled1| otherwise.
      1. If |otherCanceled| is false,
@@ -2429,6 +2441,9 @@ create them does not matter.
      1. Otherwise, if |byobCanceled| is false, perform !
         [$ReadableByteStreamControllerRespondWithNewView$](|byobBranch|.[=ReadableStream/[[controller]]=],
         |chunk|).
+     1. Set |reading| to false.
+     1. If |readAgainForBranch1| is true, perform |pull1Algorithm|.
+     1. Otherwise, if |readAgainForBranch2| is true, perform |pull2Algorithm|.
 
     <p class="note">The microtask delay here is necessary because it takes at least a microtask to
     detect errors, when we use |reader|.[=ReadableStreamGenericReader/[[closedPromise]]=] below.
@@ -2460,14 +2475,18 @@ create them does not matter.
     1. Set |reading| to false.
   1. Perform ! [$ReadableStreamBYOBReaderRead$](|reader|, |view|, |readIntoRequest|).
  1. Let |pull1Algorithm| be the following steps:
-  1. If |reading| is true, return [=a promise resolved with=] undefined.
+  1. If |reading| is true,
+   1. Set |readAgainForBranch1| to true.
+   1. Return [=a promise resolved with=] undefined.
   1. Set |reading| to true.
   1. Let |byobRequest| be ! [$ReadableByteStreamControllerGetBYOBRequest$](|branch1|.[=ReadableStream/[[controller]]=]).
   1. If |byobRequest| is null, perform |pullWithDefaultReader|.
   1. Otherwise, perform |pullWithBYOBReader|, given |byobRequest|.[=ReadableStreamBYOBRequest/[[view]]=] and false.
   1. Return [=a promise resolved with=] undefined.
  1. Let |pull2Algorithm| be the following steps:
-  1. If |reading| is true, return [=a promise resolved with=] undefined.
+  1. If |reading| is true,
+   1. Set |readAgainForBranch2| to true.
+   1. Return [=a promise resolved with=] undefined.
   1. Set |reading| to true.
   1. Let |byobRequest| be ! [$ReadableByteStreamControllerGetBYOBRequest$](|branch2|.[=ReadableStream/[[controller]]=]).
   1. If |byobRequest| is null, perform |pullWithDefaultReader|.

reference-implementation/lib/abstract-ops/readable-streams.js

@@ -348,6 +348,7 @@ function ReadableStreamDefaultTee(stream, cloneForBranch2) {
   const reader = AcquireReadableStreamDefaultReader(stream);
 
   let reading = false;
+  let readAgain = false;
   let canceled1 = false;
   let canceled2 = false;
   let reason1;
@@ -359,6 +360,7 @@ function ReadableStreamDefaultTee(stream, cloneForBranch2) {
 
   function pullAlgorithm() {
     if (reading === true) {
+      readAgain = true;
       return promiseResolvedWith(undefined);
     }
 
@@ -370,7 +372,7 @@ function ReadableStreamDefaultTee(stream, cloneForBranch2) {
         // reader._closedPromise below), and we want errors in stream to error both branches immediately. We cannot let
         // successful synchronously-available reads get ahead of asynchronously-available errors.
         queueMicrotask(() => {
-          reading = false;
+          readAgain = false;
           const chunk1 = chunk;
           const chunk2 = chunk;
 
@@ -390,10 +392,14 @@ function ReadableStreamDefaultTee(stream, cloneForBranch2) {
           if (canceled1 === false) {
             ReadableStreamDefaultControllerEnqueue(branch1._controller, chunk1);
           }
-
           if (canceled2 === false) {
             ReadableStreamDefaultControllerEnqueue(branch2._controller, chunk2);
           }
+
+          reading = false;
+          if (readAgain === true) {
+            pullAlgorithm();
+          }
         });
       },
       closeSteps: () => {
@@ -460,6 +466,8 @@ function ReadableByteStreamTee(stream) {
   assert(ReadableByteStreamController.isImpl(stream._controller));
 
   let reader = AcquireReadableStreamDefaultReader(stream);
+  let readAgainForBranch1 = false;
+  let readAgainForBranch2 = false;
   let reading = false;
   let canceled1 = false;
   let canceled2 = false;
@@ -498,7 +506,8 @@ function ReadableByteStreamTee(stream) {
         // reader._closedPromise below), and we want errors in stream to error both branches immediately. We cannot let
         // successful synchronously-available reads get ahead of asynchronously-available errors.
         queueMicrotask(() => {
-          reading = false;
+          readAgainForBranch1 = false;
+          readAgainForBranch2 = false;
 
           const chunk1 = chunk;
           let chunk2 = chunk;
@@ -519,6 +528,13 @@ function ReadableByteStreamTee(stream) {
           if (canceled2 === false) {
             ReadableByteStreamControllerEnqueue(branch2._controller, chunk2);
           }
+
+          reading = false;
+          if (readAgainForBranch1 === true) {
+            pull1Algorithm();
+          } else if (readAgainForBranch2 === true) {
+            pull2Algorithm();
+          }
         });
       },
       closeSteps: () => {
@@ -564,7 +580,8 @@ function ReadableByteStreamTee(stream) {
         // reader._closedPromise below), and we want errors in stream to error both branches immediately. We cannot let
         // successful synchronously-available reads get ahead of asynchronously-available errors.
         queueMicrotask(() => {
-          reading = false;
+          readAgainForBranch1 = false;
+          readAgainForBranch2 = false;
 
           const byobCanceled = forBranch2 ? canceled2 : canceled1;
           const otherCanceled = forBranch2 ? canceled1 : canceled2;
@@ -586,6 +603,13 @@ function ReadableByteStreamTee(stream) {
           } else if (byobCanceled === false) {
             ReadableByteStreamControllerRespondWithNewView(byobBranch._controller, chunk);
           }
+
+          reading = false;
+          if (readAgainForBranch1 === true) {
+            pull1Algorithm();
+          } else if (readAgainForBranch2 === true) {
+            pull2Algorithm();
+          }
         });
       },
       closeSteps: chunk => {
@@ -625,6 +649,7 @@ function ReadableByteStreamTee(stream) {
 
   function pull1Algorithm() {
     if (reading === true) {
+      readAgainForBranch1 = true;
       return promiseResolvedWith(undefined);
     }
 
@@ -642,6 +667,7 @@ function ReadableByteStreamTee(stream) {
 
   function pull2Algorithm() {
     if (reading === true) {
+      readAgainForBranch2 = true;
       return promiseResolvedWith(undefined);
     }