feat(extensions): BroadcastChannel WPT conformance

Replaces the file-backed provider by an in-memory one because proper
file locking is a hard problem that detracts from the proof of concept.

Teach the WPT runner how to extract tests from .html files because all
the relevant tests in test_util/wpt/webmessaging/broadcastchannel are
inside basics.html and interface.html.

5 files changed, 272 insertions, 110 deletions

diff --git a/extensions/broadcast_channel/01_broadcast_channel.js b/extensions/broadcast_channel/01_broadcast_channel.js
index 34f8b9e19..7670b0cfd 100644
--- a/extensions/broadcast_channel/01_broadcast_channel.js
+++ b/extensions/broadcast_channel/01_broadcast_channel.js
@@ -4,6 +4,7 @@
 ((window) => {
   const core = window.Deno.core;
   const webidl = window.__bootstrap.webidl;
+  const { setTarget } = window.__bootstrap.event;
 
   const handlerSymbol = Symbol("eventHandlers");
   function makeWrappedHandler(handler) {
@@ -21,7 +22,10 @@
     // HTML specification section 8.1.5.1
     Object.defineProperty(emitter, `on${name}`, {
       get() {
-        return this[handlerSymbol]?.get(name)?.handler;
+        // TODO(bnoordhuis) The "BroadcastChannel should have an onmessage
+        // event" WPT test expects that .onmessage !== undefined. Returning
+        // null makes it pass but is perhaps not exactly in the spirit.
+        return this[handlerSymbol]?.get(name)?.handler ?? null;
       },
       set(value) {
         if (!this[handlerSymbol]) {
@@ -43,12 +47,56 @@
 
   const _name = Symbol("[[name]]");
   const _closed = Symbol("[[closed]]");
-  const _rid = Symbol("[[rid]]");
+
+  const channels = [];
+  let rid = null;
+
+  async function recv() {
+    while (channels.length > 0) {
+      const message = await core.opAsync("op_broadcast_recv", rid);
+
+      if (message === null) {
+        break;
+      }
+
+      const [name, data] = message;
+      dispatch(null, name, new Uint8Array(data));
+    }
+
+    core.close(rid);
+    rid = null;
+  }
+
+  function dispatch(source, name, data) {
+    for (const channel of channels) {
+      if (channel === source) continue; // Don't self-send.
+      if (channel[_name] !== name) continue;
+      if (channel[_closed]) continue;
+
+      const go = () => {
+        if (channel[_closed]) return;
+        const event = new MessageEvent("message", {
+          data: core.deserialize(data), // TODO(bnoordhuis) Cache immutables.
+          origin: "http://127.0.0.1",
+        });
+        setTarget(event, channel);
+        channel.dispatchEvent(event);
+      };
+
+      defer(go);
+    }
+  }
+
+  // Defer to avoid starving the event loop. Not using queueMicrotask()
+  // for that reason: it lets promises make forward progress but can
+  // still starve other parts of the event loop.
+  function defer(go) {
+    setTimeout(go, 1);
+  }
 
   class BroadcastChannel extends EventTarget {
     [_name];
     [_closed] = false;
-    [_rid];
 
     get name() {
       return this[_name];
@@ -57,8 +105,6 @@
     constructor(name) {
       super();
 
-      window.location;
-
       const prefix = "Failed to construct 'broadcastChannel'";
       webidl.requiredArguments(arguments.length, 1, { prefix });
 
@@ -67,46 +113,50 @@
         context: "Argument 1",
       });
 
-      this[_rid] = core.opSync("op_broadcast_open", this[_name]);
-
       this[webidl.brand] = webidl.brand;
 
-      this.#eventLoop();
+      channels.push(this);
+
+      if (rid === null) {
+        // Create the rid immediately, otherwise there is a time window (and a
+        // race condition) where messages can get lost, because recv() is async.
+        rid = core.opSync("op_broadcast_subscribe");
+        recv();
+      }
     }
 
     postMessage(message) {
       webidl.assertBranded(this, BroadcastChannel);
 
+      const prefix = "Failed to execute 'postMessage' on 'BroadcastChannel'";
+      webidl.requiredArguments(arguments.length, 1, { prefix });
+
       if (this[_closed]) {
         throw new DOMException("Already closed", "InvalidStateError");
       }
 
-      core.opAsync("op_broadcast_send", this[_rid], core.serialize(message));
+      if (typeof message === "function" || typeof message === "symbol") {
+        throw new DOMException("Uncloneable value", "DataCloneError");
+      }
+
+      const data = core.serialize(message);
+
+      // Send to other listeners in this VM.
+      dispatch(this, this[_name], new Uint8Array(data));
+
+      // Send to listeners in other VMs.
+      defer(() => core.opAsync("op_broadcast_send", [rid, this[_name]], data));
     }
 
     close() {
       webidl.assertBranded(this, BroadcastChannel);
-
       this[_closed] = true;
-      core.close(this[_rid]);
-    }
 
-    async #eventLoop() {
-      while (!this[_closed]) {
-        const message = await core.opAsync(
-          "op_broadcast_next_event",
-          this[_rid],
-        );
-
-        if (message.length !== 0) {
-          const event = new MessageEvent("message", {
-            data: core.deserialize(message),
-            origin: window.location,
-          });
-          event.target = this;
-          this.dispatchEvent(event);
-        }
-      }
+      const index = channels.indexOf(this);
+      if (index === -1) return;
+
+      channels.splice(index, 1);
+      if (channels.length === 0) core.opSync("op_broadcast_unsubscribe", rid);
     }
   }
 
diff --git a/extensions/broadcast_channel/Cargo.toml b/extensions/broadcast_channel/Cargo.toml
index 72c29f651..7bc65f3a0 100644
--- a/extensions/broadcast_channel/Cargo.toml
+++ b/extensions/broadcast_channel/Cargo.toml
@@ -14,5 +14,7 @@ repository = "https://github.com/denoland/deno"
 path = "lib.rs"
 
 [dependencies]
+async-trait = "0.1"
 deno_core = { version = "0.88.0", path = "../../core" }
 tokio = { version = "1.4.0", features = ["full"] }
+uuid = { version = "0.8.2", features = ["v4"] }
diff --git a/extensions/broadcast_channel/in_memory_broadcast_channel.rs b/extensions/broadcast_channel/in_memory_broadcast_channel.rs
new file mode 100644
index 000000000..34498c830
--- /dev/null
+++ b/extensions/broadcast_channel/in_memory_broadcast_channel.rs
@@ -0,0 +1,97 @@
+// Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
+
+use crate::BroadcastChannel;
+use async_trait::async_trait;
+use deno_core::error::AnyError;
+use std::sync::Arc;
+use std::sync::Mutex;
+use tokio::sync::broadcast;
+use tokio::sync::mpsc;
+use uuid::Uuid;
+
+#[derive(Clone)]
+pub struct InMemoryBroadcastChannel(Arc<Mutex<broadcast::Sender<Message>>>);
+
+pub struct InMemoryBroadcastChannelResource {
+  rx: tokio::sync::Mutex<(
+    broadcast::Receiver<Message>,
+    mpsc::UnboundedReceiver<()>,
+  )>,
+  cancel_tx: mpsc::UnboundedSender<()>,
+  uuid: Uuid,
+}
+
+#[derive(Clone, Debug)]
+struct Message {
+  name: Arc<String>,
+  data: Arc<Vec<u8>>,
+  uuid: Uuid,
+}
+
+impl Default for InMemoryBroadcastChannel {
+  fn default() -> Self {
+    let (tx, _) = broadcast::channel(256);
+    Self(Arc::new(Mutex::new(tx)))
+  }
+}
+
+#[async_trait]
+impl BroadcastChannel for InMemoryBroadcastChannel {
+  type Resource = InMemoryBroadcastChannelResource;
+
+  fn subscribe(&self) -> Result<Self::Resource, AnyError> {
+    let (cancel_tx, cancel_rx) = mpsc::unbounded_channel();
+    let broadcast_rx = self.0.lock().unwrap().subscribe();
+    let rx = tokio::sync::Mutex::new((broadcast_rx, cancel_rx));
+    let uuid = Uuid::new_v4();
+    Ok(Self::Resource {
+      rx,
+      cancel_tx,
+      uuid,
+    })
+  }
+
+  fn unsubscribe(&self, resource: &Self::Resource) -> Result<(), AnyError> {
+    Ok(resource.cancel_tx.send(())?)
+  }
+
+  async fn send(
+    &self,
+    resource: &Self::Resource,
+    name: String,
+    data: Vec<u8>,
+  ) -> Result<(), AnyError> {
+    let name = Arc::new(name);
+    let data = Arc::new(data);
+    let uuid = resource.uuid;
+    self.0.lock().unwrap().send(Message { name, data, uuid })?;
+    Ok(())
+  }
+
+  async fn recv(
+    &self,
+    resource: &Self::Resource,
+  ) -> Result<Option<crate::Message>, AnyError> {
+    let mut g = resource.rx.lock().await;
+    let (broadcast_rx, cancel_rx) = &mut *g;
+    loop {
+      let result = tokio::select! {
+        r = broadcast_rx.recv() => r,
+        _ = cancel_rx.recv() => return Ok(None),
+      };
+      use tokio::sync::broadcast::error::RecvError::*;
+      match result {
+        Err(Closed) => return Ok(None),
+        Err(Lagged(_)) => (), // Backlogged, messages dropped.
+        Ok(message) if message.uuid == resource.uuid => (), // Self-send.
+        Ok(message) => {
+          let name = String::clone(&message.name);
+          let data = Vec::clone(&message.data);
+          return Ok(Some((name, data)));
+        }
+      }
+    }
+  }
+}
+
+impl deno_core::Resource for InMemoryBroadcastChannelResource {}
diff --git a/extensions/broadcast_channel/lib.rs b/extensions/broadcast_channel/lib.rs
index cee9c3e0c..b2a79916c 100644
--- a/extensions/broadcast_channel/lib.rs
+++ b/extensions/broadcast_channel/lib.rs
@@ -1,127 +1,135 @@
 // Copyright 2018-2021 the Deno authors. All rights reserved. MIT license.
 
+mod in_memory_broadcast_channel;
+
+pub use in_memory_broadcast_channel::InMemoryBroadcastChannel;
+
+use async_trait::async_trait;
 use deno_core::error::bad_resource_id;
 use deno_core::error::AnyError;
 use deno_core::include_js_files;
 use deno_core::op_async;
 use deno_core::op_sync;
-use deno_core::AsyncRefCell;
 use deno_core::Extension;
 use deno_core::OpState;
-use deno_core::RcRef;
 use deno_core::Resource;
 use deno_core::ResourceId;
 use deno_core::ZeroCopyBuf;
-use std::borrow::Cow;
 use std::cell::RefCell;
 use std::path::PathBuf;
 use std::rc::Rc;
-use tokio::io::AsyncReadExt;
-use tokio::io::AsyncWriteExt;
 
-struct BroadcastChannelResource(AsyncRefCell<tokio::fs::File>);
+#[async_trait]
+pub trait BroadcastChannel: Clone {
+  type Resource: Resource;
 
-impl Resource for BroadcastChannelResource {
-  fn name(&self) -> Cow<str> {
-    "broadcastChannel".into()
-  }
+  fn subscribe(&self) -> Result<Self::Resource, AnyError>;
+
+  fn unsubscribe(&self, resource: &Self::Resource) -> Result<(), AnyError>;
+
+  async fn send(
+    &self,
+    resource: &Self::Resource,
+    name: String,
+    data: Vec<u8>,
+  ) -> Result<(), AnyError>;
+
+  async fn recv(
+    &self,
+    resource: &Self::Resource,
+  ) -> Result<Option<Message>, AnyError>;
 }
 
-pub fn op_broadcast_open(
+pub type Message = (String, Vec<u8>);
+
+struct Unstable(bool); // --unstable
+
+pub fn op_broadcast_subscribe<BC: BroadcastChannel + 'static>(
   state: &mut OpState,
-  name: String,
-  _bufs: Option<ZeroCopyBuf>,
+  _args: (),
+  _buf: (),
 ) -> Result<ResourceId, AnyError> {
-  let path = PathBuf::from("./");
-  std::fs::create_dir_all(&path)?;
-  let file = std::fs::OpenOptions::new()
-    .create(true)
-    .append(true)
-    .read(true)
-    .open(path.join(format!("broadcast_{}", name)))?;
-
-  let rid =
-    state
-      .resource_table
-      .add(BroadcastChannelResource(AsyncRefCell::new(
-        tokio::fs::File::from_std(file),
-      )));
-
-  Ok(rid)
+  let unstable = state.borrow::<Unstable>().0;
+
+  if !unstable {
+    eprintln!(
+      "Unstable API 'BroadcastChannel'. The --unstable flag must be provided.",
+    );
+    std::process::exit(70);
+  }
+
+  let bc = state.borrow::<BC>();
+  let resource = bc.subscribe()?;
+  Ok(state.resource_table.add(resource))
 }
 
-pub async fn op_broadcast_send(
-  state: Rc<RefCell<OpState>>,
+pub fn op_broadcast_unsubscribe<BC: BroadcastChannel + 'static>(
+  state: &mut OpState,
   rid: ResourceId,
-  buf: Option<ZeroCopyBuf>,
+  _buf: (),
 ) -> Result<(), AnyError> {
-  let state = state.borrow_mut();
   let resource = state
     .resource_table
-    .get::<BroadcastChannelResource>(rid)
+    .get::<BC::Resource>(rid)
     .ok_or_else(bad_resource_id)?;
+  let bc = state.borrow::<BC>();
+  bc.unsubscribe(&resource)
+}
 
-  let mut file = RcRef::map(&resource, |r| &r.0).borrow_mut().await;
-
-  let buffer_data = buf.unwrap();
-  let mut data = vec![];
-  data.extend_from_slice(&(buffer_data.len() as u64).to_ne_bytes());
-  data.extend_from_slice(&buffer_data);
-
-  file.write_all(&data).await?;
-
-  Ok(())
+pub async fn op_broadcast_send<BC: BroadcastChannel + 'static>(
+  state: Rc<RefCell<OpState>>,
+  (rid, name): (ResourceId, String),
+  buf: ZeroCopyBuf,
+) -> Result<(), AnyError> {
+  let resource = state
+    .borrow()
+    .resource_table
+    .get::<BC::Resource>(rid)
+    .ok_or_else(bad_resource_id)?;
+  let bc = state.borrow().borrow::<BC>().clone();
+  bc.send(&resource, name, buf.to_vec()).await
 }
 
-pub async fn op_broadcast_next_event(
+pub async fn op_broadcast_recv<BC: BroadcastChannel + 'static>(
   state: Rc<RefCell<OpState>>,
   rid: ResourceId,
-  _bufs: Option<ZeroCopyBuf>,
-) -> Result<Vec<u8>, AnyError> {
-  let resource = {
-    let state = state.borrow_mut();
-    state
-      .resource_table
-      .get::<BroadcastChannelResource>(rid)
-      .ok_or_else(bad_resource_id)?
-  };
-
-  let mut file = RcRef::map(&resource, |r| &r.0).borrow_mut().await;
-
-  let size = match file.read_u64().await {
-    Ok(s) => s,
-    Err(e) => {
-      return match e.kind() {
-        deno_core::futures::io::ErrorKind::UnexpectedEof => Ok(vec![]),
-        _ => Err(e.into()),
-      }
-    }
-  };
-  let mut data = vec![0u8; size as usize];
-  match file.read_exact(&mut data).await {
-    Ok(s) => s,
-    Err(e) => {
-      return match e.kind() {
-        deno_core::futures::io::ErrorKind::UnexpectedEof => Ok(vec![]),
-        _ => Err(e.into()),
-      }
-    }
-  };
-
-  Ok(data)
+  _buf: (),
+) -> Result<Option<Message>, AnyError> {
+  let resource = state
+    .borrow()
+    .resource_table
+    .get::<BC::Resource>(rid)
+    .ok_or_else(bad_resource_id)?;
+  let bc = state.borrow().borrow::<BC>().clone();
+  bc.recv(&resource).await
 }
 
-pub fn init() -> Extension {
+pub fn init<BC: BroadcastChannel + 'static>(
+  bc: BC,
+  unstable: bool,
+) -> Extension {
   Extension::builder()
     .js(include_js_files!(
       prefix "deno:extensions/broadcast_channel",
       "01_broadcast_channel.js",
     ))
     .ops(vec![
-      ("op_broadcast_open", op_sync(op_broadcast_open)),
-      ("op_broadcast_send", op_async(op_broadcast_send)),
-      ("op_broadcast_next_event", op_async(op_broadcast_next_event)),
+      (
+        "op_broadcast_subscribe",
+        op_sync(op_broadcast_subscribe::<BC>),
+      ),
+      (
+        "op_broadcast_unsubscribe",
+        op_sync(op_broadcast_unsubscribe::<BC>),
+      ),
+      ("op_broadcast_send", op_async(op_broadcast_send::<BC>)),
+      ("op_broadcast_recv", op_async(op_broadcast_recv::<BC>)),
     ])
+    .state(move |state| {
+      state.put(bc.clone());
+      state.put(Unstable(unstable));
+      Ok(())
+    })
     .build()
 }
 
diff --git a/extensions/web/02_event.js b/extensions/web/02_event.js
index b6b5609bc..8ee6acc61 100644
--- a/extensions/web/02_event.js
+++ b/extensions/web/02_event.js
@@ -1117,6 +1117,10 @@
   }
 
   class MessageEvent extends Event {
+    get source() {
+      return null;
+    }
+
     constructor(type, eventInitDict) {
       super(type, {
         bubbles: eventInitDict?.bubbles ?? false,
@@ -1208,5 +1212,6 @@
   };
   window.__bootstrap.event = {
     setIsTrusted,
+    setTarget,
   };
 })(this);