script: Implement set_up, ReleaseLock, Closed, Cancel, acquire_byob_reader for ReadableStreamBYOBReader (#34958)

* introduce ReadableStreamGenericReader to share functionality between ReadableStreamDefaultReader and ReadableStreamBYOBReader

Signed-off-by: Taym Haddadi <haddadi.taym@gmail.com>

* implement set_up, ReleaseLock, Closed, Cancel for ReadableStreamBYOBReader

Signed-off-by: Taym Haddadi <haddadi.taym@gmail.com>

* Fix clippy

Signed-off-by: Taym Haddadi <haddadi.taym@gmail.com>

* Implement acquire_byob_reader

Signed-off-by: Taym Haddadi <haddadi.taym@gmail.com>

* Remove #[allow(crown::unrooted_must_root)] from ReadRequest and ReadIntoRequest

Signed-off-by: Taym Haddadi <haddadi.taym@gmail.com>

* Fix clippy

Signed-off-by: Taym Haddadi <haddadi.taym@gmail.com>

---------

Signed-off-by: Taym Haddadi <haddadi.taym@gmail.com>

components/script/dom/bindings/codegen/Bindings.conf

@@ -547,7 +547,7 @@ DOMInterfaces = {
 },
 
 "ReadableStreamBYOBReader": {
-    "canGc": ["Read", "Closed", "Cancel"]
+    "canGc": ["Read", "Cancel"]
 },
 
 "ReadableStreamDefaultReader": {

components/script/dom/mod.rs

@@ -501,6 +501,7 @@ pub(crate) mod readablestreambyobreader;
 pub(crate) mod readablestreambyobrequest;
 pub(crate) mod readablestreamdefaultcontroller;
 pub(crate) mod readablestreamdefaultreader;
+pub(crate) mod readablestreamgenericreader;
 pub(crate) mod request;
 pub(crate) mod resizeobserver;
 pub(crate) mod resizeobserverentry;

components/script/dom/readablestream.rs

@@ -26,7 +26,7 @@ use crate::dom::bindings::conversions::{ConversionBehavior, ConversionResult};
 use crate::dom::bindings::error::Error;
 use crate::dom::bindings::import::module::Fallible;
 use crate::dom::bindings::import::module::UnionTypes::ReadableStreamDefaultReaderOrReadableStreamBYOBReader as ReadableStreamReader;
-use crate::dom::bindings::reflector::{DomObject, Reflector, reflect_dom_object, reflect_dom_object_with_proto};
+use crate::dom::bindings::reflector::{DomObject, Reflector, reflect_dom_object_with_proto};
 use crate::dom::bindings::root::{DomRoot, MutNullableDom, Dom};
 use crate::dom::bindings::trace::RootedTraceableBox;
 use crate::dom::bindings::utils::get_dictionary_property;
@@ -277,12 +277,12 @@ impl ReadableStream {
     }
 
     /// Call into the release steps of the controller,
-    pub(crate) fn perform_release_steps(&self) {
-        match self.controller {
-            ControllerType::Default(ref controller) => controller
+    pub(crate) fn perform_release_steps(&self) -> Fallible<()> {
+        match &self.controller {
+            ControllerType::Default(controller) => controller
                 .get()
-                .expect("Stream should have controller.")
-                .perform_release_steps(),
+                .map(|controller_ref| controller_ref.perform_release_steps())
+                .unwrap_or_else(|| Err(Error::Type("Stream should have controller.".to_string()))),
             ControllerType::Byte(_) => todo!(),
         }
     }
@@ -426,14 +426,7 @@ impl ReadableStream {
         can_gc: CanGc,
     ) -> Fallible<DomRoot<ReadableStreamDefaultReader>> {
         // Let reader be a new ReadableStreamDefaultReader.
-        let reader = reflect_dom_object(
-            Box::new(ReadableStreamDefaultReader::new_inherited(
-                &self.global(),
-                can_gc,
-            )),
-            &*self.global(),
-            can_gc,
-        );
+        let reader = ReadableStreamDefaultReader::new(&self.global(), can_gc);
 
         // Perform ? SetUpReadableStreamDefaultReader(reader, stream).
         reader.set_up(self, &self.global(), can_gc)?;
@@ -442,6 +435,20 @@ impl ReadableStream {
         Ok(reader)
     }
 
+    /// <https://streams.spec.whatwg.org/#acquire-readable-stream-byob-reader>
+    pub(crate) fn acquire_byob_reader(
+        &self,
+        can_gc: CanGc,
+    ) -> Fallible<DomRoot<ReadableStreamBYOBReader>> {
+        // Let reader be a new ReadableStreamBYOBReader.
+        let reader = ReadableStreamBYOBReader::new(&self.global(), can_gc);
+        // Perform ? SetUpReadableStreamBYOBReader(reader, stream).
+        reader.set_up(self, &self.global(), can_gc)?;
+
+        // Return reader.
+        Ok(reader)
+    }
+
     pub(crate) fn get_default_controller(&self) -> DomRoot<ReadableStreamDefaultController> {
         match self.controller {
             ControllerType::Default(ref controller) => {
@@ -484,7 +491,7 @@ impl ReadableStream {
                 let Some(reader) = reader.get() else {
                     unreachable!("Attempt to stop reading without having first acquired a reader.");
                 };
-                reader.release();
+                reader.release().expect("Reader release cannot fail.");
             },
             ReaderType::BYOB(_) => {
                 unreachable!("Native stop reading can only be done with a default reader.")
@@ -527,6 +534,10 @@ impl ReadableStream {
         }
     }
 
+    pub(crate) fn has_byte_controller(&self) -> bool {
+        matches!(self.controller, ControllerType::Byte(_))
+    }
+
     /// <https://streams.spec.whatwg.org/#readable-stream-get-num-read-requests>
     pub(crate) fn get_num_read_requests(&self) -> usize {
         assert!(self.has_default_reader());
@@ -592,7 +603,7 @@ impl ReadableStream {
                 // step 5 & 6
                 reader.close();
             },
-            ReaderType::BYOB(ref _reader) => todo!(),
+            ReaderType::BYOB(ref _reader) => {},
         }
     }
 
@@ -621,8 +632,17 @@ impl ReadableStream {
         }
         // Perform ! ReadableStreamClose(stream).
         self.close();
-        // step 5, 6, 7, 8
-        // TODO: run the bytes reader steps.
+
+        // If reader is not undefined and reader implements ReadableStreamBYOBReader,
+        match self.reader {
+            ReaderType::BYOB(ref reader) => {
+                if let Some(reader) = reader.get() {
+                    // step 6.1, 6.2 & 6.3 of https://streams.spec.whatwg.org/#readable-stream-cancel
+                    reader.close();
+                }
+            },
+            ReaderType::Default(ref _reader) => {},
+        }
 
         // Let sourceCancelPromise be ! stream.[[controller]].[[CancelSteps]](reason).
         let source_cancel_promise = match self.controller {
@@ -656,16 +676,27 @@ impl ReadableStream {
         result_promise
     }
 
-    pub(crate) fn set_reader(&self, new_reader: Option<&ReadableStreamDefaultReader>) {
-        match self.reader {
-            ReaderType::Default(ref reader) => {
-                reader.set(new_reader);
+    #[allow(crown::unrooted_must_root)]
+    pub(crate) fn set_reader(&self, new_reader: Option<ReaderType>) {
+        match (&self.reader, new_reader) {
+            (ReaderType::Default(ref reader), Some(ReaderType::Default(new_reader))) => {
+                reader.set(new_reader.get().as_deref());
             },
-            ReaderType::BYOB(_) => {
-                unreachable!("Setting a reader can only be done on a default reader.")
+            (ReaderType::BYOB(ref reader), Some(ReaderType::BYOB(new_reader))) => {
+                reader.set(new_reader.get().as_deref());
+            },
+            (ReaderType::Default(ref reader), None) => {
+                reader.set(None);
+            },
+            (ReaderType::BYOB(ref reader), None) => {
+                reader.set(None);
+            },
+            (_, _) => {
+                unreachable!("Setting a mismatched reader type is not allowed.");
             },
         }
     }
+
     /// <https://streams.spec.whatwg.org/#abstract-opdef-readablestreamdefaulttee>
     #[allow(crown::unrooted_must_root)]
     fn default_tee(
@@ -680,7 +711,9 @@ impl ReadableStream {
 
         // Let reader be ? AcquireReadableStreamDefaultReader(stream).
         let reader = self.acquire_default_reader(can_gc)?;
-        self.set_reader(Some(&reader));
+        self.set_reader(Some(ReaderType::Default(MutNullableDom::new(Some(
+            &reader,
+        )))));
 
         // Let reading be false.
         let reading = Rc::new(Cell::new(false));
@@ -874,7 +907,7 @@ impl ReadableStreamMethods<crate::DomTypeHolder> for ReadableStream {
         if self.is_locked() {
             // If ! IsReadableStreamLocked(this) is true,
             // return a promise rejected with a TypeError exception.
-            let promise = Promise::new(&self.reflector_.global(), can_gc);
+            let promise = Promise::new(&self.global(), can_gc);
             promise.reject_error(Error::Type("stream is not locked".to_owned()));
             promise
         } else {
@@ -899,8 +932,8 @@ impl ReadableStreamMethods<crate::DomTypeHolder> for ReadableStream {
         assert!(options.mode.unwrap() == ReadableStreamReaderMode::Byob);
 
         // 3. Return ? AcquireReadableStreamBYOBReader(this).
-        Err(Error::Type(
-            "AcquireReadableStreamBYOBReader is not implemented".to_owned(),
+        Ok(ReadableStreamReader::ReadableStreamBYOBReader(
+            self.acquire_byob_reader(can_gc)?,
         ))
     }
 

components/script/dom/readablestreambyobreader.rs

@@ -1,58 +1,196 @@
 /* This Source Code Form is subject to the terms of the Mozilla Public
  * License, v. 2.0. If a copy of the MPL was not distributed with this
  * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
 #![allow(dead_code)]
 
+use std::collections::VecDeque;
+use std::mem;
 use std::rc::Rc;
 
 use dom_struct::dom_struct;
 use js::gc::CustomAutoRooterGuard;
+use js::jsapi::Heap;
+use js::jsval::{JSVal, UndefinedValue};
 use js::rust::{HandleObject as SafeHandleObject, HandleValue as SafeHandleValue};
 use js::typedarray::ArrayBufferView;
 
+use super::bindings::reflector::reflect_dom_object;
+use super::readablestreamgenericreader::ReadableStreamGenericReader;
+use crate::dom::bindings::cell::DomRefCell;
 use crate::dom::bindings::codegen::Bindings::ReadableStreamBYOBReaderBinding::ReadableStreamBYOBReaderMethods;
 use crate::dom::bindings::error::Error;
 use crate::dom::bindings::import::module::Fallible;
-use crate::dom::bindings::reflector::{reflect_dom_object, DomObject, Reflector};
-use crate::dom::bindings::root::DomRoot;
+use crate::dom::bindings::reflector::{reflect_dom_object_with_proto, DomObject, Reflector};
+use crate::dom::bindings::root::{DomRoot, MutNullableDom};
+use crate::dom::bindings::trace::RootedTraceableBox;
 use crate::dom::globalscope::GlobalScope;
 use crate::dom::promise::Promise;
 use crate::dom::readablestream::ReadableStream;
 use crate::script_runtime::{CanGc, JSContext as SafeJSContext};
 
+/// <https://streams.spec.whatwg.org/#read-into-request>
+#[derive(JSTraceable, MallocSizeOf)]
+pub enum ReadIntoRequest {
+    /// <https://streams.spec.whatwg.org/#byob-reader-read>
+    Read(#[ignore_malloc_size_of = "Rc is hard"] Rc<Promise>),
+}
+
+impl ReadIntoRequest {
+    /// <https://streams.spec.whatwg.org/#read-into-request-chunk-steps>
+    pub fn chunk_steps(&self, _chunk: RootedTraceableBox<Heap<JSVal>>) {
+        todo!()
+    }
+
+    /// <https://streams.spec.whatwg.org/#read-into-request-close-steps>
+    pub fn close_steps(&self, _chunk: Option<RootedTraceableBox<Heap<JSVal>>>) {
+        todo!()
+    }
+
+    /// <https://streams.spec.whatwg.org/#read-into-request-error-steps>
+    pub(crate) fn error_steps(&self, _e: SafeHandleValue) {
+        todo!()
+    }
+}
+
 /// <https://streams.spec.whatwg.org/#readablestreambyobreader>
 #[dom_struct]
 pub(crate) struct ReadableStreamBYOBReader {
     reflector_: Reflector,
+
+    /// <https://streams.spec.whatwg.org/#readablestreamgenericreader-stream>
+    stream: MutNullableDom<ReadableStream>,
+
+    read_into_requests: DomRefCell<VecDeque<ReadIntoRequest>>,
+
+    /// <https://streams.spec.whatwg.org/#readablestreamgenericreader-closedpromise>
+    #[ignore_malloc_size_of = "Rc is hard"]
+    closed_promise: DomRefCell<Rc<Promise>>,
 }
 
 impl ReadableStreamBYOBReader {
-    fn new_inherited() -> ReadableStreamBYOBReader {
+    fn new_with_proto(
+        global: &GlobalScope,
+        proto: Option<SafeHandleObject>,
+        can_gc: CanGc,
+    ) -> DomRoot<ReadableStreamBYOBReader> {
+        reflect_dom_object_with_proto(
+            Box::new(ReadableStreamBYOBReader::new_inherited(global, can_gc)),
+            global,
+            proto,
+            can_gc,
+        )
+    }
+
+    fn new_inherited(global: &GlobalScope, can_gc: CanGc) -> ReadableStreamBYOBReader {
         ReadableStreamBYOBReader {
             reflector_: Reflector::new(),
+            stream: MutNullableDom::new(None),
+            read_into_requests: DomRefCell::new(Default::default()),
+            closed_promise: DomRefCell::new(Promise::new(global, can_gc)),
         }
     }
 
-    fn new(global: &GlobalScope, can_gc: CanGc) -> DomRoot<ReadableStreamBYOBReader> {
+    pub(crate) fn new(global: &GlobalScope, can_gc: CanGc) -> DomRoot<ReadableStreamBYOBReader> {
         reflect_dom_object(
-            Box::new(ReadableStreamBYOBReader::new_inherited()),
+            Box::new(Self::new_inherited(global, can_gc)),
             global,
             can_gc,
         )
     }
+
+    /// <https://streams.spec.whatwg.org/#set-up-readable-stream-byob-reader>
+    pub(crate) fn set_up(
+        &self,
+        stream: &ReadableStream,
+        global: &GlobalScope,
+        can_gc: CanGc,
+    ) -> Fallible<()> {
+        // If ! IsReadableStreamLocked(stream) is true, throw a TypeError exception.
+        if stream.is_locked() {
+            return Err(Error::Type("stream is locked".to_owned()));
+        }
+
+        // If stream.[[controller]] does not implement ReadableByteStreamController, throw a TypeError exception.
+        if !stream.has_byte_controller() {
+            return Err(Error::Type(
+                "stream controller is not a byte stream controller".to_owned(),
+            ));
+        }
+
+        // Perform ! ReadableStreamReaderGenericInitialize(reader, stream).
+        self.generic_initialize(global, stream, can_gc)?;
+
+        // Set reader.[[readIntoRequests]] to a new empty list.
+        self.read_into_requests.borrow_mut().clear();
+
+        Ok(())
+    }
+
+    /// <https://streams.spec.whatwg.org/#abstract-opdef-readablestreambyobreaderrelease>
+    #[allow(unsafe_code)]
+    pub(crate) fn release(&self) -> Fallible<()> {
+        // Perform ! ReadableStreamReaderGenericRelease(reader).
+        self.generic_release()?;
+        // Let e be a new TypeError exception.
+        let cx = GlobalScope::get_cx();
+        rooted!(in(*cx) let mut error = UndefinedValue());
+        unsafe {
+            Error::Type("Reader is released".to_owned()).to_jsval(
+                *cx,
+                &self.global(),
+                error.handle_mut(),
+            )
+        };
+
+        // Perform ! ReadableStreamBYOBReaderErrorReadIntoRequests(reader, e).
+        self.error_read_into_requests(error.handle());
+        Ok(())
+    }
+
+    /// <https://streams.spec.whatwg.org/#abstract-opdef-readablestreambyobreadererrorreadintorequests>
+    fn error_read_into_requests(&self, rval: SafeHandleValue) {
+        // Let readRequests be reader.[[readRequests]].
+        let mut read_into_requests = self.take_read_into_requests();
+
+        // Set reader.[[readIntoRequests]] to a new empty list.
+        for request in read_into_requests.drain(0..) {
+            // Perform readIntoRequest’s error steps, given e.
+            request.error_steps(rval);
+        }
+    }
+
+    fn take_read_into_requests(&self) -> VecDeque<ReadIntoRequest> {
+        mem::take(&mut *self.read_into_requests.borrow_mut())
+    }
+
+    /// <https://streams.spec.whatwg.org/#readable-stream-cancel>
+    pub(crate) fn close(&self) {
+        // If reader is not undefined and reader implements ReadableStreamBYOBReader,
+        // Let readIntoRequests be reader.[[readIntoRequests]].
+        let mut read_into_requests = self.take_read_into_requests();
+        // Set reader.[[readIntoRequests]] to an empty list.
+        // Perform readIntoRequest’s close steps, given undefined.
+        for request in read_into_requests.drain(0..) {
+            // Perform readIntoRequest’s close steps, given undefined.
+            request.close_steps(None);
+        }
+    }
 }
 
 impl ReadableStreamBYOBReaderMethods<crate::DomTypeHolder> for ReadableStreamBYOBReader {
     /// <https://streams.spec.whatwg.org/#byob-reader-constructor>
     fn Constructor(
-        _global: &GlobalScope,
-        _proto: Option<SafeHandleObject>,
-        _can_gc: CanGc,
-        _stream: &ReadableStream,
+        global: &GlobalScope,
+        proto: Option<SafeHandleObject>,
+        can_gc: CanGc,
+        stream: &ReadableStream,
     ) -> Fallible<DomRoot<Self>> {
-        // TODO
-        Err(Error::NotFound)
+        let reader = Self::new_with_proto(global, proto, can_gc);
+
+        // Perform ? SetUpReadableStreamBYOBReader(this, stream).
+        Self::set_up(&reader, stream, global, can_gc)?;
+
+        Ok(reader)
     }
 
     /// <https://streams.spec.whatwg.org/#byob-reader-read>
@@ -63,19 +201,44 @@ impl ReadableStreamBYOBReaderMethods<crate::DomTypeHolder> for ReadableStreamBYO
 
     /// <https://streams.spec.whatwg.org/#byob-reader-release-lock>
     fn ReleaseLock(&self) -> Fallible<()> {
-        // TODO
-        Err(Error::NotFound)
+        if self.stream.get().is_none() {
+            // If this.[[stream]] is undefined, return.
+            return Ok(());
+        }
+
+        // Perform !ReadableStreamBYOBReaderRelease(this).
+        self.release()
     }
 
     /// <https://streams.spec.whatwg.org/#generic-reader-closed>
-    fn Closed(&self, can_gc: CanGc) -> Rc<Promise> {
-        // TODO
-        Promise::new(&self.reflector_.global(), can_gc)
+    fn Closed(&self) -> Rc<Promise> {
+        self.closed()
     }
 
     /// <https://streams.spec.whatwg.org/#generic-reader-cancel>
-    fn Cancel(&self, _cx: SafeJSContext, _reason: SafeHandleValue, can_gc: CanGc) -> Rc<Promise> {
-        // TODO
-        Promise::new(&self.reflector_.global(), can_gc)
+    fn Cancel(&self, _cx: SafeJSContext, reason: SafeHandleValue, can_gc: CanGc) -> Rc<Promise> {
+        self.cancel(&self.global(), reason, can_gc)
+    }
+}
+
+impl ReadableStreamGenericReader for ReadableStreamBYOBReader {
+    fn get_closed_promise(&self) -> Rc<Promise> {
+        self.closed_promise.borrow().clone()
+    }
+
+    fn set_closed_promise(&self, promise: Rc<Promise>) {
+        *self.closed_promise.borrow_mut() = promise;
+    }
+
+    fn set_stream(&self, stream: Option<&ReadableStream>) {
+        self.stream.set(stream);
+    }
+
+    fn get_stream(&self) -> Option<DomRoot<ReadableStream>> {
+        self.stream.get()
+    }
+
+    fn as_byob_reader(&self) -> Option<&ReadableStreamBYOBReader> {
+        Some(self)
     }
 }

components/script/dom/readablestreamdefaultcontroller.rs

@@ -612,8 +612,9 @@ impl ReadableStreamDefaultController {
     }
 
     /// <https://streams.spec.whatwg.org/#ref-for-abstract-opdef-readablestreamcontroller-releasesteps>
-    pub(crate) fn perform_release_steps(&self) {
+    pub(crate) fn perform_release_steps(&self) -> Fallible<()> {
         // step 1 - Return.
+        Ok(())
     }
 
     /// <https://streams.spec.whatwg.org/#readable-stream-default-controller-enqueue>

components/script/dom/readablestreamdefaultreader.rs

@@ -12,6 +12,7 @@ use js::jsapi::Heap;
 use js::jsval::{JSVal, UndefinedValue};
 use js::rust::{HandleObject as SafeHandleObject, HandleValue as SafeHandleValue};
 
+use super::bindings::reflector::reflect_dom_object;
 use super::bindings::root::MutNullableDom;
 use super::types::ReadableStreamDefaultController;
 use crate::dom::bindings::cell::DomRefCell;
@@ -28,15 +29,15 @@ use crate::dom::globalscope::GlobalScope;
 use crate::dom::promise::Promise;
 use crate::dom::promisenativehandler::{Callback, PromiseNativeHandler};
 use crate::dom::readablestream::ReadableStream;
+use crate::dom::readablestreamgenericreader::ReadableStreamGenericReader;
 use crate::realms::{enter_realm, InRealm};
 use crate::script_runtime::{CanGc, JSContext as SafeJSContext};
 
 /// <https://streams.spec.whatwg.org/#read-request>
-#[derive(Clone, JSTraceable)]
-#[crown::unrooted_must_root_lint::must_root]
+#[derive(Clone, JSTraceable, MallocSizeOf)]
 pub(crate) enum ReadRequest {
     /// <https://streams.spec.whatwg.org/#default-reader-read>
-    Read(Rc<Promise>),
+    Read(#[ignore_malloc_size_of = "Rc is hard"] Rc<Promise>),
     /// <https://streams.spec.whatwg.org/#ref-for-read-request%E2%91%A2>
     DefaultTee {
         tee_read_request: Dom<DefaultTeeReadRequest>,
@@ -129,7 +130,6 @@ pub(crate) struct ReadableStreamDefaultReader {
     /// <https://streams.spec.whatwg.org/#readablestreamgenericreader-stream>
     stream: MutNullableDom<ReadableStream>,
 
-    #[ignore_malloc_size_of = "no VecDeque support"]
     read_requests: DomRefCell<VecDeque<ReadRequest>>,
 
     /// <https://streams.spec.whatwg.org/#readablestreamgenericreader-closedpromise>
@@ -138,22 +138,6 @@ pub(crate) struct ReadableStreamDefaultReader {
 }
 
 impl ReadableStreamDefaultReader {
-    /// <https://streams.spec.whatwg.org/#default-reader-constructor>
-    #[allow(non_snake_case)]
-    pub(crate) fn Constructor(
-        global: &GlobalScope,
-        proto: Option<SafeHandleObject>,
-        can_gc: CanGc,
-        stream: &ReadableStream,
-    ) -> Fallible<DomRoot<Self>> {
-        let reader = Self::new_with_proto(global, proto, can_gc);
-
-        // Perform ? SetUpReadableStreamDefaultReader(this, stream).
-        Self::set_up(&reader, stream, global, can_gc)?;
-
-        Ok(reader)
-    }
-
     fn new_with_proto(
         global: &GlobalScope,
         proto: Option<SafeHandleObject>,
@@ -167,10 +151,7 @@ impl ReadableStreamDefaultReader {
         )
     }
 
-    pub(crate) fn new_inherited(
-        global: &GlobalScope,
-        can_gc: CanGc,
-    ) -> ReadableStreamDefaultReader {
+    fn new_inherited(global: &GlobalScope, can_gc: CanGc) -> ReadableStreamDefaultReader {
         ReadableStreamDefaultReader {
             reflector_: Reflector::new(),
             stream: MutNullableDom::new(None),
@@ -179,6 +160,14 @@ impl ReadableStreamDefaultReader {
         }
     }
 
+    pub(crate) fn new(global: &GlobalScope, can_gc: CanGc) -> DomRoot<ReadableStreamDefaultReader> {
+        reflect_dom_object(
+            Box::new(Self::new_inherited(global, can_gc)),
+            global,
+            can_gc,
+        )
+    }
+
     /// <https://streams.spec.whatwg.org/#set-up-readable-stream-default-reader>
     pub(crate) fn set_up(
         &self,
@@ -200,48 +189,7 @@ impl ReadableStreamDefaultReader {
         Ok(())
     }
 
-    /// <https://streams.spec.whatwg.org/#readable-stream-reader-generic-initialize>
-    pub(crate) fn generic_initialize(
-        &self,
-        global: &GlobalScope,
-        stream: &ReadableStream,
-        can_gc: CanGc,
-    ) -> Fallible<()> {
-        // Set reader.[[stream]] to stream.
-        self.stream.set(Some(stream));
-
-        // Set stream.[[reader]] to reader.
-        stream.set_reader(Some(self));
-
-        if stream.is_readable() {
-            // If stream.[[state]] is "readable
-            // Set reader.[[closedPromise]] to a new promise.
-            *self.closed_promise.borrow_mut() = Promise::new(global, can_gc);
-        } else if stream.is_closed() {
-            // Otherwise, if stream.[[state]] is "closed",
-            // Set reader.[[closedPromise]] to a promise resolved with undefined.
-            let cx = GlobalScope::get_cx();
-            rooted!(in(*cx) let mut rval = UndefinedValue());
-            *self.closed_promise.borrow_mut() = Promise::new_resolved(global, cx, rval.handle())?;
-        } else {
-            // Assert: stream.[[state]] is "errored"
-            assert!(stream.is_errored());
-
-            // Set reader.[[closedPromise]] to a promise rejected with stream.[[storedError]].
-            let cx = GlobalScope::get_cx();
-            rooted!(in(*cx) let mut error = UndefinedValue());
-            stream.get_stored_error(error.handle_mut());
-            *self.closed_promise.borrow_mut() = Promise::new_rejected(global, cx, error.handle())?;
-
-            // Set reader.[[closedPromise]].[[PromiseIsHandled]] to true
-            self.closed_promise.borrow().set_promise_is_handled();
-        }
-
-        Ok(())
-    }
-
     /// <https://streams.spec.whatwg.org/#readable-stream-close>
-    #[allow(crown::unrooted_must_root)]
     pub(crate) fn close(&self) {
         // Resolve reader.[[closedPromise]] with undefined.
         self.closed_promise.borrow().resolve_native(&());
@@ -281,7 +229,6 @@ impl ReadableStreamDefaultReader {
     }
 
     /// The removal steps of <https://streams.spec.whatwg.org/#readable-stream-fulfill-read-request>
-    #[allow(crown::unrooted_must_root)]
     pub(crate) fn remove_read_request(&self) -> ReadRequest {
         self.read_requests
             .borrow_mut()
@@ -289,56 +236,11 @@ impl ReadableStreamDefaultReader {
             .expect("Reader must have read request when remove is called into.")
     }
 
-    /// <https://streams.spec.whatwg.org/#readable-stream-reader-generic-release>
-    #[allow(unsafe_code)]
-    pub(crate) fn generic_release(&self) {
-        // Let stream be reader.[[stream]].
-
-        // Assert: stream is not undefined.
-        assert!(self.stream.get().is_some());
-
-        if let Some(stream) = self.stream.get() {
-            // Assert: stream.[[reader]] is reader.
-            assert!(stream.has_default_reader());
-
-            if stream.is_readable() {
-                // If stream.[[state]] is "readable", reject reader.[[closedPromise]] with a TypeError exception.
-                self.closed_promise
-                    .borrow()
-                    .reject_error(Error::Type("stream state is not readable".to_owned()));
-            } else {
-                // Otherwise, set reader.[[closedPromise]] to a promise rejected with a TypeError exception.
-                let cx = GlobalScope::get_cx();
-                rooted!(in(*cx) let mut error = UndefinedValue());
-                unsafe {
-                    Error::Type("Cannot release lock due to stream state.".to_owned()).to_jsval(
-                        *cx,
-                        &self.global(),
-                        error.handle_mut(),
-                    )
-                };
-
-                *self.closed_promise.borrow_mut() =
-                    Promise::new_rejected(&self.global(), cx, error.handle()).unwrap();
-            }
-            // Set reader.[[closedPromise]].[[PromiseIsHandled]] to true.
-            self.closed_promise.borrow().set_promise_is_handled();
-
-            // Perform ! stream.[[controller]].[[ReleaseSteps]]().
-            stream.perform_release_steps();
-
-            // Set stream.[[reader]] to undefined.
-            stream.set_reader(None);
-            // Set reader.[[stream]] to undefined.
-            self.stream.set(None);
-        }
-    }
-
     /// <https://streams.spec.whatwg.org/#abstract-opdef-readablestreamdefaultreaderrelease>
     #[allow(unsafe_code)]
-    pub(crate) fn release(&self) {
+    pub(crate) fn release(&self) -> Fallible<()> {
         // Perform ! ReadableStreamReaderGenericRelease(reader).
-        self.generic_release();
+        self.generic_release()?;
         // Let e be a new TypeError exception.
         let cx = GlobalScope::get_cx();
         rooted!(in(*cx) let mut error = UndefinedValue());
@@ -352,28 +254,14 @@ impl ReadableStreamDefaultReader {
 
         // Perform ! ReadableStreamDefaultReaderErrorReadRequests(reader, e).
         self.error_read_requests(error.handle());
+        Ok(())
     }
 
-    #[allow(crown::unrooted_must_root)]
     fn take_read_requests(&self) -> VecDeque<ReadRequest> {
         mem::take(&mut *self.read_requests.borrow_mut())
     }
 
-    /// <https://streams.spec.whatwg.org/#readable-stream-reader-generic-cancel>
-    fn generic_cancel(&self, reason: SafeHandleValue, can_gc: CanGc) -> Rc<Promise> {
-        // Let stream be reader.[[stream]].
-        let stream = self.stream.get();
-
-        // Assert: stream is not undefined.
-        let stream =
-            stream.expect("Reader should have a stream when generic cancel is called into.");
-
-        // Return ! ReadableStreamCancel(stream, reason).
-        stream.cancel(reason, can_gc)
-    }
-
     /// <https://streams.spec.whatwg.org/#abstract-opdef-readablestreamdefaultreadererrorreadrequests>
-    #[allow(crown::unrooted_must_root)]
     fn error_read_requests(&self, rval: SafeHandleValue) {
         // step 1
         let mut read_requests = self.take_read_requests();
@@ -458,12 +346,16 @@ impl ReadableStreamDefaultReaderMethods<crate::DomTypeHolder> for ReadableStream
         can_gc: CanGc,
         stream: &ReadableStream,
     ) -> Fallible<DomRoot<Self>> {
-        ReadableStreamDefaultReader::Constructor(global, proto, can_gc, stream)
+        let reader = Self::new_with_proto(global, proto, can_gc);
+
+        // Perform ? SetUpReadableStreamDefaultReader(this, stream).
+        Self::set_up(&reader, stream, global, can_gc)?;
+
+        Ok(reader)
     }
 
     /// <https://streams.spec.whatwg.org/#default-reader-read>
     #[allow(unsafe_code)]
-    #[allow(crown::unrooted_must_root)]
     fn Read(&self, can_gc: CanGc) -> Rc<Promise> {
         // If this.[[stream]] is undefined, return a promise rejected with a TypeError exception.
         if self.stream.get().is_none() {
@@ -504,30 +396,45 @@ impl ReadableStreamDefaultReaderMethods<crate::DomTypeHolder> for ReadableStream
     }
 
     /// <https://streams.spec.whatwg.org/#default-reader-release-lock>
-    fn ReleaseLock(&self) {
-        if self.stream.get().is_some() {
-            // step 2 - Perform ! ReadableStreamDefaultReaderRelease(this).
-            self.release();
+    fn ReleaseLock(&self) -> Fallible<()> {
+        if self.stream.get().is_none() {
+            // Step 1: If this.[[stream]] is undefined, return.
+            return Ok(());
         }
-        // step 1 - If this.[[stream]] is undefined, return.
+
+        // Step 2: Perform !ReadableStreamDefaultReaderRelease(this).
+        self.release()
     }
 
     /// <https://streams.spec.whatwg.org/#generic-reader-closed>
     fn Closed(&self) -> Rc<Promise> {
-        self.closed_promise.borrow().clone()
+        self.closed()
     }
 
     /// <https://streams.spec.whatwg.org/#generic-reader-cancel>
     fn Cancel(&self, _cx: SafeJSContext, reason: SafeHandleValue, can_gc: CanGc) -> Rc<Promise> {
-        if self.stream.get().is_none() {
-            // If this.[[stream]] is undefined,
-            // return a promise rejected with a TypeError exception.
-            let promise = Promise::new(&self.reflector_.global(), can_gc);
-            promise.reject_error(Error::Type("stream is undefined".to_owned()));
-            promise
-        } else {
-            // Return ! ReadableStreamReaderGenericCancel(this, reason).
-            self.generic_cancel(reason, can_gc)
-        }
+        self.cancel(&self.global(), reason, can_gc)
+    }
+}
+
+impl ReadableStreamGenericReader for ReadableStreamDefaultReader {
+    fn get_closed_promise(&self) -> Rc<Promise> {
+        self.closed_promise.borrow().clone()
+    }
+
+    fn set_closed_promise(&self, promise: Rc<Promise>) {
+        *self.closed_promise.borrow_mut() = promise;
+    }
+
+    fn set_stream(&self, stream: Option<&ReadableStream>) {
+        self.stream.set(stream);
+    }
+
+    fn get_stream(&self) -> Option<DomRoot<ReadableStream>> {
+        self.stream.get()
+    }
+
+    fn as_default_reader(&self) -> Option<&ReadableStreamDefaultReader> {
+        Some(self)
     }
 }

components/script/dom/readablestreamgenericreader.rs

@@ -0,0 +1,164 @@
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+use std::rc::Rc;
+
+use js::jsval::UndefinedValue;
+use js::rust::HandleValue as SafeHandleValue;
+
+use super::readablestream::ReaderType;
+use super::types::ReadableStream;
+use crate::dom::bindings::error::Error;
+use crate::dom::bindings::import::module::Fallible;
+use crate::dom::bindings::reflector::DomObject;
+use crate::dom::bindings::root::{DomRoot, MutNullableDom};
+use crate::dom::globalscope::GlobalScope;
+use crate::dom::promise::Promise;
+use crate::dom::readablestreambyobreader::ReadableStreamBYOBReader;
+use crate::dom::readablestreamdefaultreader::ReadableStreamDefaultReader;
+use crate::script_runtime::CanGc;
+
+/// <https://streams.spec.whatwg.org/#readablestreamgenericreader>
+pub(crate) trait ReadableStreamGenericReader {
+    /// <https://streams.spec.whatwg.org/#readable-stream-reader-generic-initialize>
+    #[allow(crown::unrooted_must_root)]
+    fn generic_initialize(
+        &self,
+        global: &GlobalScope,
+        stream: &ReadableStream,
+        can_gc: CanGc,
+    ) -> Fallible<()> {
+        // Set reader.[[stream]] to stream.
+        self.set_stream(Some(stream));
+
+        // Set stream.[[reader]] to reader.
+        let reader_type = if let Some(default_reader) = self.as_default_reader() {
+            ReaderType::Default(MutNullableDom::new(Some(default_reader)))
+        } else if let Some(byob_reader) = self.as_byob_reader() {
+            ReaderType::BYOB(MutNullableDom::new(Some(byob_reader)))
+        } else {
+            unreachable!("Reader must be either Default or BYOB.");
+        };
+        stream.set_reader(Some(reader_type));
+
+        if stream.is_readable() {
+            // If stream.[[state]] is "readable
+            // Set reader.[[closedPromise]] to a new promise.
+            self.set_closed_promise(Promise::new(global, can_gc));
+        } else if stream.is_closed() {
+            // Otherwise, if stream.[[state]] is "closed",
+            // Set reader.[[closedPromise]] to a promise resolved with undefined.
+            let cx = GlobalScope::get_cx();
+            self.set_closed_promise(Promise::new_resolved(global, cx, ())?);
+        } else {
+            // Assert: stream.[[state]] is "errored"
+            assert!(stream.is_errored());
+
+            // Set reader.[[closedPromise]] to a promise rejected with stream.[[storedError]].
+            let cx = GlobalScope::get_cx();
+            rooted!(in(*cx) let mut error = UndefinedValue());
+            stream.get_stored_error(error.handle_mut());
+            self.set_closed_promise(Promise::new_rejected(global, cx, error.handle())?);
+
+            // Set reader.[[closedPromise]].[[PromiseIsHandled]] to true
+            self.get_closed_promise().set_promise_is_handled();
+        }
+
+        Ok(())
+    }
+
+    /// <https://streams.spec.whatwg.org/#readable-stream-reader-generic-cancel>
+    fn generic_cancel(&self, reason: SafeHandleValue, can_gc: CanGc) -> Rc<Promise> {
+        // Let stream be reader.[[stream]].
+        let stream = self.get_stream();
+
+        // Assert: stream is not undefined.
+        let stream =
+            stream.expect("Reader should have a stream when generic cancel is called into.");
+
+        // Return ! ReadableStreamCancel(stream, reason).
+        stream.cancel(reason, can_gc)
+    }
+
+    /// <https://streams.spec.whatwg.org/#readable-stream-reader-generic-release>
+    #[allow(unsafe_code)]
+    fn generic_release(&self) -> Fallible<()> {
+        // Let stream be reader.[[stream]].
+
+        // Assert: stream is not undefined.
+        assert!(self.get_stream().is_some());
+
+        if let Some(stream) = self.get_stream() {
+            // Assert: stream.[[reader]] is reader.
+            assert!(stream.has_default_reader());
+
+            if stream.is_readable() {
+                // If stream.[[state]] is "readable", reject reader.[[closedPromise]] with a TypeError exception.
+                self.get_closed_promise()
+                    .reject_error(Error::Type("stream state is not readable".to_owned()));
+            } else {
+                // Otherwise, set reader.[[closedPromise]] to a promise rejected with a TypeError exception.
+                let cx = GlobalScope::get_cx();
+                rooted!(in(*cx) let mut error = UndefinedValue());
+                unsafe {
+                    Error::Type("Cannot release lock due to stream state.".to_owned()).to_jsval(
+                        *cx,
+                        &stream.global(),
+                        error.handle_mut(),
+                    )
+                };
+
+                self.set_closed_promise(
+                    Promise::new_rejected(&stream.global(), cx, error.handle()).unwrap(),
+                );
+            }
+            // Set reader.[[closedPromise]].[[PromiseIsHandled]] to true.
+            self.get_closed_promise().set_promise_is_handled();
+
+            // Perform ! stream.[[controller]].[[ReleaseSteps]]().
+            stream.perform_release_steps()?;
+
+            // Set stream.[[reader]] to undefined.
+            stream.set_reader(None);
+            // Set reader.[[stream]] to undefined.
+            self.set_stream(None);
+        }
+        Ok(())
+    }
+
+    /// <https://streams.spec.whatwg.org/#generic-reader-closed>
+    fn closed(&self) -> Rc<Promise> {
+        self.get_closed_promise()
+    }
+
+    // <https://streams.spec.whatwg.org/#generic-reader-cancel>
+    fn cancel(&self, global: &GlobalScope, reason: SafeHandleValue, can_gc: CanGc) -> Rc<Promise> {
+        if self.get_stream().is_none() {
+            // If this.[[stream]] is undefined,
+            // return a promise rejected with a TypeError exception.
+            let promise = Promise::new(global, can_gc);
+            promise.reject_error(Error::Type("stream is undefined".to_owned()));
+            promise
+        } else {
+            // Return ! ReadableStreamReaderGenericCancel(this, reason).
+            self.generic_cancel(reason, can_gc)
+        }
+    }
+
+    fn set_stream(&self, stream: Option<&ReadableStream>);
+
+    fn get_stream(&self) -> Option<DomRoot<ReadableStream>>;
+
+    fn set_closed_promise(&self, promise: Rc<Promise>);
+
+    fn get_closed_promise(&self) -> Rc<Promise>;
+
+    fn as_default_reader(&self) -> Option<&ReadableStreamDefaultReader> {
+        None
+    }
+
+    fn as_byob_reader(&self) -> Option<&ReadableStreamBYOBReader> {
+        None
+    }
+}

components/script/dom/webidls/ReadableStreamDefaultReader.webidl

@@ -22,6 +22,7 @@ interface ReadableStreamDefaultReader {
   [NewObject]
   Promise<ReadableStreamReadResult> read();
 
+  [Throws]
   undefined releaseLock();
 };
 ReadableStreamDefaultReader includes ReadableStreamGenericReader;