LibWeb: Implement TransformStream transfer

Author: https://github.com/trflynn89
Commit: 95fc0a8070
Pull-request: https://github.com/LadybirdBrowser/ladybird/pull/4828
Reviewed-by: https://github.com/shannonbooth ✅

Libraries/LibWeb/HTML/StructuredSerialize.cpp

@@ -50,6 +50,7 @@
 #include <LibWeb/HTML/MessagePort.h>
 #include <LibWeb/HTML/StructuredSerialize.h>
 #include <LibWeb/Streams/ReadableStream.h>
+#include <LibWeb/Streams/TransformStream.h>
 #include <LibWeb/Streams/WritableStream.h>
 #include <LibWeb/WebIDL/DOMException.h>
 #include <LibWeb/WebIDL/ExceptionOr.h>
@@ -1299,6 +1300,8 @@ static bool is_interface_exposed_on_target_realm(TransferType name, JS::Realm& r
         return intrinsics.is_exposed("ReadableStream"sv);
     case TransferType::WritableStream:
         return intrinsics.is_exposed("WritableStream"sv);
+    case TransferType::TransformStream:
+        return intrinsics.is_exposed("TransformStream"sv);
     case TransferType::Unknown:
         dbgln("Unknown interface type for transfer: {}", to_underlying(name));
         break;
@@ -1326,6 +1329,11 @@ static WebIDL::ExceptionOr<GC::Ref<Bindings::PlatformObject>> create_transferred
         TRY(writable_stream->transfer_receiving_steps(transfer_data_holder));
         return writable_stream;
     }
+    case TransferType::TransformStream: {
+        auto transform_stream = target_realm.create<Streams::TransformStream>(target_realm);
+        TRY(transform_stream->transfer_receiving_steps(transfer_data_holder));
+        return transform_stream;
+    }
     case TransferType::ArrayBuffer:
     case TransferType::ResizableArrayBuffer:
         dbgln("ArrayBuffer ({}) is not a platform object.", to_underlying(name));

Libraries/LibWeb/HTML/StructuredSerialize.h

@@ -51,6 +51,7 @@ enum class TransferType : u8 {
     ResizableArrayBuffer = 3,
     ReadableStream = 4,
     WritableStream = 5,
+    TransformStream = 6,
 };
 
 WebIDL::ExceptionOr<SerializationRecord> structured_serialize(JS::VM& vm, JS::Value);

Libraries/LibWeb/Streams/TransformStream.cpp

@@ -4,15 +4,18 @@
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <LibIPC/File.h>
 #include <LibWeb/Bindings/Intrinsics.h>
 #include <LibWeb/Bindings/TransformStreamPrototype.h>
 #include <LibWeb/Streams/AbstractOperations.h>
 #include <LibWeb/Streams/ReadableStream.h>
+#include <LibWeb/Streams/ReadableStreamOperations.h>
 #include <LibWeb/Streams/TransformStream.h>
 #include <LibWeb/Streams/TransformStreamDefaultController.h>
 #include <LibWeb/Streams/TransformStreamOperations.h>
 #include <LibWeb/Streams/Transformer.h>
 #include <LibWeb/Streams/WritableStream.h>
+#include <LibWeb/Streams/WritableStreamOperations.h>
 #include <LibWeb/WebIDL/AbstractOperations.h>
 #include <LibWeb/WebIDL/ExceptionOr.h>
 
@@ -76,6 +79,28 @@ WebIDL::ExceptionOr<GC::Ref<TransformStream>> TransformStream::construct_impl(JS
     return stream;
 }
 
+TransformStream::TransformStream(JS::Realm& realm)
+    : Bindings::PlatformObject(realm)
+{
+}
+
+TransformStream::~TransformStream() = default;
+
+void TransformStream::initialize(JS::Realm& realm)
+{
+    WEB_SET_PROTOTYPE_FOR_INTERFACE(TransformStream);
+    Base::initialize(realm);
+}
+
+void TransformStream::visit_edges(Cell::Visitor& visitor)
+{
+    Base::visit_edges(visitor);
+    visitor.visit(m_backpressure_change_promise);
+    visitor.visit(m_controller);
+    visitor.visit(m_readable);
+    visitor.visit(m_writable);
+}
+
 // https://streams.spec.whatwg.org/#transformstream-enqueue
 void TransformStream::enqueue(JS::Value chunk)
 {
@@ -161,26 +186,83 @@ void TransformStream::set_up(GC::Ref<TransformAlgorithm> transform_algorithm, GC
     set_up_transform_stream_default_controller(*this, controller, transform_algorithm_wrapper, flush_algorithm_wrapper, cancel_algorithm_wrapper);
 }
 
-TransformStream::TransformStream(JS::Realm& realm)
-    : Bindings::PlatformObject(realm)
+// https://streams.spec.whatwg.org/#ref-for-transfer-steps②
+WebIDL::ExceptionOr<void> TransformStream::transfer_steps(HTML::TransferDataHolder& data_holder)
 {
+    auto& realm = this->realm();
+    auto& vm = realm.vm();
+
+    auto serialize_stream = [&](auto stream) {
+        auto result = MUST(HTML::structured_serialize_with_transfer(vm, stream, { { GC::Root { stream } } }));
+
+        data_holder.data.extend(move(result.transfer_data_holders.first().data));
+        data_holder.fds.extend(move(result.transfer_data_holders.first().fds));
+    };
+
+    // 1. Let readable be value.[[readable]].
+    auto readable = this->readable();
+
+    // 2. Let writable be value.[[writable]].
+    auto writable = this->writable();
+
+    // 3. If ! IsReadableStreamLocked(readable) is true, throw a "DataCloneError" DOMException.
+    if (is_readable_stream_locked(readable))
+        return WebIDL::DataCloneError::create(realm, "Cannot transfer locked ReadableStream"_string);
+
+    // 4. If ! IsWritableStreamLocked(writable) is true, throw a "DataCloneError" DOMException.
+    if (is_writable_stream_locked(writable))
+        return WebIDL::DataCloneError::create(realm, "Cannot transfer locked WritableStream"_string);
+
+    // 5. Set dataHolder.[[readable]] to ! StructuredSerializeWithTransfer(readable, « readable »).
+    serialize_stream(readable);
+
+    // 6. Set dataHolder.[[writable]] to ! StructuredSerializeWithTransfer(writable, « writable »).
+    serialize_stream(writable);
+
+    return {};
 }
 
-TransformStream::~TransformStream() = default;
-
-void TransformStream::initialize(JS::Realm& realm)
+template<typename StreamType>
+static WebIDL::ExceptionOr<GC::Ref<StreamType>> deserialize_stream(JS::Realm& realm, HTML::TransferDataHolder& data_holder)
 {
-    WEB_SET_PROTOTYPE_FOR_INTERFACE(TransformStream);
-    Base::initialize(realm);
+    auto transfer_type = data_holder.data.take_first();
+
+    if constexpr (IsSame<StreamType, ReadableStream>)
+        VERIFY(transfer_type == to_underlying(HTML::TransferType::ReadableStream));
+    else if constexpr (IsSame<StreamType, WritableStream>)
+        VERIFY(transfer_type == to_underlying(HTML::TransferType::WritableStream));
+    else
+        static_assert(DependentFalse<StreamType>);
+
+    auto stream = realm.create<StreamType>(realm);
+    TRY(stream->transfer_receiving_steps(data_holder));
+
+    return stream;
 }
 
-void TransformStream::visit_edges(Cell::Visitor& visitor)
+// https://streams.spec.whatwg.org/#ref-for-transfer-receiving-steps②
+WebIDL::ExceptionOr<void> TransformStream::transfer_receiving_steps(HTML::TransferDataHolder& data_holder)
 {
-    Base::visit_edges(visitor);
-    visitor.visit(m_backpressure_change_promise);
-    visitor.visit(m_controller);
-    visitor.visit(m_readable);
-    visitor.visit(m_writable);
+    auto& realm = this->realm();
+
+    // 1. Let readableRecord be ! StructuredDeserializeWithTransfer(dataHolder.[[readable]], the current Realm).
+    auto readable = TRY(deserialize_stream<ReadableStream>(realm, data_holder));
+
+    // 2. Let writableRecord be ! StructuredDeserializeWithTransfer(dataHolder.[[writable]], the current Realm).
+    auto writable = TRY(deserialize_stream<WritableStream>(realm, data_holder));
+
+    // 3. Set value.[[readable]] to readableRecord.[[Deserialized]].
+    set_readable(readable);
+
+    // 4. Set value.[[writable]] to writableRecord.[[Deserialized]].
+    set_writable(writable);
+
+    // 5. Set value.[[backpressure]], value.[[backpressureChangePromise]], and value.[[controller]] to undefined.
+    set_backpressure({});
+    set_backpressure_change_promise({});
+    set_controller({});
+
+    return {};
 }
 
 }

Libraries/LibWeb/Streams/TransformStream.h

@@ -8,6 +8,7 @@
 
 #include <LibJS/Forward.h>
 #include <LibWeb/Bindings/PlatformObject.h>
+#include <LibWeb/Bindings/Transferable.h>
 #include <LibWeb/Forward.h>
 #include <LibWeb/Streams/Algorithms.h>
 #include <LibWeb/Streams/QueuingStrategy.h>
@@ -15,7 +16,9 @@
 
 namespace Web::Streams {
 
-class TransformStream final : public Bindings::PlatformObject {
+class TransformStream final
+    : public Bindings::PlatformObject
+    , public Bindings::Transferable {
     WEB_PLATFORM_OBJECT(TransformStream, Bindings::PlatformObject);
     GC_DECLARE_ALLOCATOR(TransformStream);
 
@@ -44,6 +47,11 @@ public:
     void set_up(GC::Ref<TransformAlgorithm>, GC::Ptr<FlushAlgorithm> = {}, GC::Ptr<CancelAlgorithm> = {});
     void enqueue(JS::Value chunk);
 
+    // ^Transferable
+    virtual WebIDL::ExceptionOr<void> transfer_steps(HTML::TransferDataHolder&) override;
+    virtual WebIDL::ExceptionOr<void> transfer_receiving_steps(HTML::TransferDataHolder&) override;
+    virtual HTML::TransferType primary_interface() const override { return HTML::TransferType::TransformStream; }
+
 private:
     explicit TransformStream(JS::Realm& realm);
 
@@ -63,10 +71,6 @@ private:
     // A TransformStreamDefaultController created with the ability to control [[readable]] and [[writable]]
     GC::Ptr<TransformStreamDefaultController> m_controller;
 
-    // https://streams.spec.whatwg.org/#transformstream-detached
-    // A boolean flag set to true when the stream is transferred
-    bool m_detached { false };
-
     // https://streams.spec.whatwg.org/#transformstream-readable
     // The ReadableStream instance controlled by this object
     GC::Ptr<ReadableStream> m_readable;

Tests/LibWeb/Text/expected/wpt-import/streams/transferable/transform-stream.txt

@@ -0,0 +1,10 @@
+Harness status: OK
+
+Found 5 tests
+
+5 Pass
+Pass	window.postMessage should be able to transfer a TransformStream
+Pass	a TransformStream with a locked writable should not be transferable
+Pass	a TransformStream with a locked readable should not be transferable
+Pass	a TransformStream with both sides locked should not be transferable
+Pass	piping through transferred transforms should work

Tests/LibWeb/Text/input/wpt-import/streams/transferable/transform-stream.html

@@ -0,0 +1,108 @@
+<!DOCTYPE html>
+<meta charset="utf-8">
+<script src="../../resources/testharness.js"></script>
+<script src="../../resources/testharnessreport.js"></script>
+<script src="../resources/test-utils.js"></script>
+<script>
+'use strict';
+
+promise_test(t => {
+  const orig = new TransformStream();
+  const promise = new Promise(resolve => {
+    addEventListener('message', t.step_func(evt => {
+      const transferred = evt.data;
+      assert_equals(transferred.constructor, TransformStream,
+                    'transferred should be a TransformStream in this realm');
+      assert_true(transferred instanceof TransformStream,
+                  'instanceof check should pass');
+
+      // Perform a brand-check on |transferred|.
+      const readableGetter = Object.getOwnPropertyDescriptor(
+        TransformStream.prototype, 'readable').get;
+      assert_true(readableGetter.call(transferred) instanceof ReadableStream,
+                 'brand check should pass and readable stream should result');
+      const writableGetter = Object.getOwnPropertyDescriptor(
+        TransformStream.prototype, 'writable').get;
+      assert_true(writableGetter.call(transferred) instanceof WritableStream,
+                 'brand check should pass and writable stream should result');
+      resolve();
+    }), {once: true});
+  });
+  postMessage(orig, '*', [orig]);
+  assert_true(orig.readable.locked, 'the readable side should be locked');
+  assert_true(orig.writable.locked, 'the writable side should be locked');
+  return promise;
+}, 'window.postMessage should be able to transfer a TransformStream');
+
+test(() => {
+  const ts = new TransformStream();
+  const writer = ts.writable.getWriter();
+  assert_throws_dom('DataCloneError', () => postMessage(ts, '*', [ts]),
+                    'postMessage should throw');
+  assert_false(ts.readable.locked, 'readable side should not get locked');
+}, 'a TransformStream with a locked writable should not be transferable');
+
+test(() => {
+  const ts = new TransformStream();
+  const reader = ts.readable.getReader();
+  assert_throws_dom('DataCloneError', () => postMessage(ts, '*', [ts]),
+                    'postMessage should throw');
+  assert_false(ts.writable.locked, 'writable side should not get locked');
+}, 'a TransformStream with a locked readable should not be transferable');
+
+test(() => {
+  const ts = new TransformStream();
+  const reader = ts.readable.getReader();
+  const writer = ts.writable.getWriter();
+  assert_throws_dom('DataCloneError', () => postMessage(ts, '*', [ts]),
+                    'postMessage should throw');
+}, 'a TransformStream with both sides locked should not be transferable');
+
+promise_test(t => {
+  const source = new ReadableStream({
+    start(controller) {
+      controller.enqueue('hello ');
+      controller.enqueue('there ');
+      controller.close();
+    }
+  });
+  let resolve;
+  const ready = new Promise(r => resolve = r);
+  let result = '';
+  const sink = new WritableStream({
+    write(chunk) {
+      if (result) {
+        resolve();
+      }
+      result += chunk;
+    }
+  });
+  const transform1 = new TransformStream({
+    transform(chunk, controller) {
+      controller.enqueue(chunk.toUpperCase());
+    }
+  });
+  const transform2 = new TransformStream({
+    transform(chunk, controller) {
+      controller.enqueue(chunk + chunk);
+    }
+  });
+  const promise = new Promise(resolve => {
+    addEventListener('message', t.step_func(evt => {
+      const data = evt.data;
+      resolve(data.source
+                .pipeThrough(data.transform1)
+                .pipeThrough(data.transform2)
+                .pipeTo(data.sink));
+    }));
+  });
+  postMessage({source, sink, transform1, transform2}, '*',
+              [source, transform1, sink, transform2]);
+  return ready
+    .then(() => {
+      assert_equals(result, 'HELLO HELLO THERE THERE ',
+                    'transforms should have been applied');
+    });
+}, 'piping through transferred transforms should work');
+
+</script>