From ffda698d3aa0c9c43bf4366fa2057cc5134ee1cd Mon Sep 17 00:00:00 2001
From: Shannon Booth <shannon@serenityos.org>
Date: Thu, 26 Dec 2024 12:02:07 +1300
Subject: [PATCH] LibWeb/Streams: Actually implement the piped through steps

This mistakenly implemented the 'piped to' operation on ReadableStream.
No functional difference as the caller was doing the extra work already
of 'piped through' vs 'piped to'.
---
 Libraries/LibWeb/Fetch/Fetching/Fetching.cpp |  4 +---
 Libraries/LibWeb/Streams/ReadableStream.cpp  | 17 ++++++++++++-----
 Libraries/LibWeb/Streams/ReadableStream.h    |  2 +-
 3 files changed, 14 insertions(+), 9 deletions(-)

diff --git a/Libraries/LibWeb/Fetch/Fetching/Fetching.cpp b/Libraries/LibWeb/Fetch/Fetching/Fetching.cpp
index a12e3f28bdc..a7d53956986 100644
--- a/Libraries/LibWeb/Fetch/Fetching/Fetching.cpp
+++ b/Libraries/LibWeb/Fetch/Fetching/Fetching.cpp
@@ -744,9 +744,7 @@ void fetch_response_handover(JS::Realm& realm, Infrastructure::FetchParams const
         transform_stream->set_up(identity_transform_algorithm, flush_algorithm);
 
         // 4. Set internalResponse’s body’s stream to the result of internalResponse’s body’s stream piped through transformStream.
-        auto promise = internal_response->body()->stream()->piped_through(transform_stream->writable());
-        WebIDL::mark_promise_as_handled(*promise);
-        internal_response->body()->set_stream(transform_stream->readable());
+        internal_response->body()->set_stream(internal_response->body()->stream()->piped_through(transform_stream));
     }
 
     // 8. If fetchParams’s process response consume body is non-null, then:
diff --git a/Libraries/LibWeb/Streams/ReadableStream.cpp b/Libraries/LibWeb/Streams/ReadableStream.cpp
index 742277848c6..91e1373e084 100644
--- a/Libraries/LibWeb/Streams/ReadableStream.cpp
+++ b/Libraries/LibWeb/Streams/ReadableStream.cpp
@@ -18,6 +18,7 @@
 #include <LibWeb/Streams/ReadableStreamBYOBRequest.h>
 #include <LibWeb/Streams/ReadableStreamDefaultController.h>
 #include <LibWeb/Streams/ReadableStreamDefaultReader.h>
+#include <LibWeb/Streams/TransformStream.h>
 #include <LibWeb/Streams/UnderlyingSource.h>
 #include <LibWeb/Streams/WritableStream.h>
 #include <LibWeb/WebIDL/Buffers.h>
@@ -426,19 +427,25 @@ void ReadableStream::set_up_with_byte_reading_support(GC::Ptr<PullAlgorithm> pul
 }
 
 // https://streams.spec.whatwg.org/#readablestream-pipe-through
-GC::Ref<WebIDL::Promise> ReadableStream::piped_through(GC::Ref<WritableStream> writable, bool prevent_close, bool prevent_abort, bool prevent_cancel, JS::Value signal)
+GC::Ref<ReadableStream> ReadableStream::piped_through(GC::Ref<TransformStream> transform, bool prevent_close, bool prevent_abort, bool prevent_cancel, JS::Value signal)
 {
     // 1. Assert: ! IsReadableStreamLocked(readable) is false.
     VERIFY(!is_readable_stream_locked(*this));
 
-    // 2. Assert: ! IsWritableStreamLocked(writable) is false.
-    VERIFY(!is_writable_stream_locked(writable));
+    // 2. Assert: ! IsWritableStreamLocked(transform.[[writable]]) is false.
+    VERIFY(!is_writable_stream_locked(transform->writable()));
 
     // 3. Let signalArg be signal if signal was given, or undefined otherwise.
     // NOTE: Done by default arguments.
 
-    // 4. Return ! ReadableStreamPipeTo(readable, writable, preventClose, preventAbort, preventCancel, signalArg).
-    return readable_stream_pipe_to(*this, writable, prevent_close, prevent_abort, prevent_cancel, signal);
+    // 4. Let promise be ! ReadableStreamPipeTo(readable, transform.[[writable]], preventClose, preventAbort, preventCancel, signalArg).
+    auto promise = readable_stream_pipe_to(*this, transform->writable(), prevent_close, prevent_abort, prevent_cancel, signal);
+
+    // 5. Set promise.[[PromiseIsHandled]] to true.
+    WebIDL::mark_promise_as_handled(*promise);
+
+    // 6. Return transform.[[readable]].
+    return transform->readable();
 }
 
 }
diff --git a/Libraries/LibWeb/Streams/ReadableStream.h b/Libraries/LibWeb/Streams/ReadableStream.h
index 5cfc1e66dce..af7e9f4fd8c 100644
--- a/Libraries/LibWeb/Streams/ReadableStream.h
+++ b/Libraries/LibWeb/Streams/ReadableStream.h
@@ -109,7 +109,7 @@ public:
     WebIDL::ExceptionOr<void> pull_from_bytes(ByteBuffer);
     WebIDL::ExceptionOr<void> enqueue(JS::Value chunk);
     void set_up_with_byte_reading_support(GC::Ptr<PullAlgorithm> = {}, GC::Ptr<CancelAlgorithm> = {}, double high_water_mark = 0);
-    GC::Ref<WebIDL::Promise> piped_through(GC::Ref<WritableStream>, bool prevent_close = false, bool prevent_abort = false, bool prevent_cancel = false, JS::Value signal = JS::js_undefined());
+    GC::Ref<ReadableStream> piped_through(GC::Ref<TransformStream>, bool prevent_close = false, bool prevent_abort = false, bool prevent_cancel = false, JS::Value signal = JS::js_undefined());
 
     GC::Ptr<WebIDL::ArrayBufferView> current_byob_request_view();