fix(core): module execution with top level await (#7672)

This commit fixes implementation of top level await in "deno_core".

Previously promise returned from module execution was ignored causing to execute
modules out-of-order.

With this commit promise returned from module execution is stored on "JsRuntime"
and event loop is polled until the promise resolves.

cli/ops/worker_host.rs

@@ -155,6 +155,13 @@ fn run_worker_thread(
 
     if let Err(e) = result {
       let mut sender = worker.internal_channels.sender.clone();
+
+      // If sender is closed it means that worker has already been closed from
+      // within using "globalThis.close()"
+      if sender.is_closed() {
+        return;
+      }
+
       sender
         .try_send(WorkerEvent::TerminalError(e))
         .expect("Failed to post message to host");

cli/tests/integration_tests.rs

@@ -2662,6 +2662,16 @@ itest!(ignore_require {
   exit_code: 0,
 });
 
+itest!(top_level_await_bug {
+  args: "run --allow-read top_level_await_bug.js",
+  output: "top_level_await_bug.out",
+});
+
+itest!(top_level_await_bug2 {
+  args: "run --allow-read top_level_await_bug2.js",
+  output: "top_level_await_bug2.out",
+});
+
 #[test]
 fn cafile_env_fetch() {
   use deno_core::url::Url;

cli/tests/top_level_await_bug.js

@@ -0,0 +1,2 @@
+const mod = await import("./top_level_await_bug_nested.js");
+console.log(mod);

cli/tests/top_level_await_bug.out

@@ -0,0 +1 @@
+Module { default: 1, [Symbol(Symbol.toStringTag)]: "Module" }

cli/tests/top_level_await_bug2.js

@@ -0,0 +1,15 @@
+const mod = await import("./top_level_await_bug_nested.js");
+console.log(mod);
+
+const sleep = (n) => new Promise((r) => setTimeout(r, n));
+
+await sleep(100);
+console.log("slept");
+
+window.addEventListener("load", () => {
+  console.log("load event");
+});
+
+setTimeout(() => {
+  console.log("timeout");
+}, 1000);

cli/tests/top_level_await_bug2.out

@@ -0,0 +1,4 @@
+Module { default: 1, [Symbol(Symbol.toStringTag)]: "Module" }
+slept
+load event
+timeout

cli/tests/top_level_await_bug_nested.js

@@ -0,0 +1,5 @@
+const sleep = (n) => new Promise((r) => setTimeout(r, n));
+
+await sleep(100);
+
+export default 1;

cli/worker.rs

@@ -189,7 +189,7 @@ impl Worker {
   ) -> Result<(), AnyError> {
     let id = self.preload_module(module_specifier).await?;
     self.wait_for_inspector_session();
-    self.isolate.mod_evaluate(id)
+    self.isolate.mod_evaluate(id).await
   }
 
   /// Loads, instantiates and executes provided source code
@@ -204,7 +204,7 @@ impl Worker {
       .load_module(module_specifier, Some(code))
       .await?;
     self.wait_for_inspector_session();
-    self.isolate.mod_evaluate(id)
+    self.isolate.mod_evaluate(id).await
   }
 
   /// Returns a way to communicate with the Worker from other threads.

core/modules.rs

@@ -341,6 +341,13 @@ pub struct ModuleInfo {
   pub name: String,
   pub handle: v8::Global<v8::Module>,
   pub import_specifiers: Vec<ModuleSpecifier>,
+  // TODO(bartlomieju): there should be "state"
+  // field that describes if module is already being loaded,
+  // so concurent dynamic imports don't introduce dead lock
+  // pub state: LoadState {
+  //   Loading(shared_future),
+  //   Loaded,
+  // },
 }
 
 /// A symbolic module entity.
@@ -667,7 +674,7 @@ mod tests {
     let a_id_fut = runtime.load_module(&spec, None);
     let a_id = futures::executor::block_on(a_id_fut).expect("Failed to load");
 
-    runtime.mod_evaluate(a_id).unwrap();
+    futures::executor::block_on(runtime.mod_evaluate(a_id)).unwrap();
     let l = loads.lock().unwrap();
     assert_eq!(
       l.to_vec(),
@@ -734,7 +741,7 @@ mod tests {
       let result = runtime.load_module(&spec, None).await;
       assert!(result.is_ok());
       let circular1_id = result.unwrap();
-      runtime.mod_evaluate(circular1_id).unwrap();
+      runtime.mod_evaluate(circular1_id).await.unwrap();
 
       let l = loads.lock().unwrap();
       assert_eq!(
@@ -811,7 +818,7 @@ mod tests {
       println!(">> result {:?}", result);
       assert!(result.is_ok());
       let redirect1_id = result.unwrap();
-      runtime.mod_evaluate(redirect1_id).unwrap();
+      runtime.mod_evaluate(redirect1_id).await.unwrap();
       let l = loads.lock().unwrap();
       assert_eq!(
         l.to_vec(),
@@ -961,7 +968,7 @@ mod tests {
     let main_id =
       futures::executor::block_on(main_id_fut).expect("Failed to load");
 
-    runtime.mod_evaluate(main_id).unwrap();
+    futures::executor::block_on(runtime.mod_evaluate(main_id)).unwrap();
 
     let l = loads.lock().unwrap();
     assert_eq!(

core/runtime.rs

@@ -23,6 +23,8 @@ use crate::shared_queue::SharedQueue;
 use crate::shared_queue::RECOMMENDED_SIZE;
 use crate::BufVec;
 use crate::OpState;
+use futures::channel::mpsc;
+use futures::future::poll_fn;
 use futures::stream::FuturesUnordered;
 use futures::stream::StreamExt;
 use futures::stream::StreamFuture;
@@ -84,6 +86,11 @@ pub struct JsRuntime {
   allocations: IsolateAllocations,
 }
 
+type DynImportModEvaluate =
+  (ModuleId, v8::Global<v8::Promise>, v8::Global<v8::Module>);
+type ModEvaluate =
+  (v8::Global<v8::Promise>, mpsc::Sender<Result<(), AnyError>>);
+
 /// Internal state for JsRuntime which is stored in one of v8::Isolate's
 /// embedder slots.
 pub(crate) struct JsRuntimeState {
@@ -92,6 +99,8 @@ pub(crate) struct JsRuntimeState {
   pub(crate) js_recv_cb: Option<v8::Global<v8::Function>>,
   pub(crate) js_macrotask_cb: Option<v8::Global<v8::Function>>,
   pub(crate) pending_promise_exceptions: HashMap<i32, v8::Global<v8::Value>>,
+  pub(crate) pending_dyn_mod_evaluate: HashMap<i32, DynImportModEvaluate>,
+  pub(crate) pending_mod_evaluate: HashMap<ModuleId, ModEvaluate>,
   pub(crate) js_error_create_fn: Box<JsErrorCreateFn>,
   pub(crate) shared: SharedQueue,
   pub(crate) pending_ops: FuturesUnordered<PendingOpFuture>,
@@ -278,6 +287,8 @@ impl JsRuntime {
     isolate.set_slot(Rc::new(RefCell::new(JsRuntimeState {
       global_context: Some(global_context),
       pending_promise_exceptions: HashMap::new(),
+      pending_dyn_mod_evaluate: HashMap::new(),
+      pending_mod_evaluate: HashMap::new(),
       shared_ab: None,
       js_recv_cb: None,
       js_macrotask_cb: None,
@@ -484,6 +495,9 @@ impl Future for JsRuntime {
       state.waker.register(cx.waker());
     }
 
+    // Top level modules
+    runtime.poll_mod_evaluate(cx)?;
+
     // Dynamic module loading - ie. modules loaded using "import()"
     {
       let poll_imports = runtime.prepare_dyn_imports(cx)?;
@@ -492,6 +506,8 @@ impl Future for JsRuntime {
       let poll_imports = runtime.poll_dyn_imports(cx)?;
       assert!(poll_imports.is_ready());
 
+      runtime.poll_dyn_imports_evaluate(cx)?;
+
       runtime.check_promise_exceptions()?;
     }
 
@@ -508,6 +524,8 @@ impl Future for JsRuntime {
       state.pending_ops.is_empty()
         && state.pending_dyn_imports.is_empty()
         && state.preparing_dyn_imports.is_empty()
+        && state.pending_dyn_mod_evaluate.is_empty()
+        && state.pending_mod_evaluate.is_empty()
     };
 
     if is_idle {
@@ -700,7 +718,91 @@ impl JsRuntime {
   /// `AnyError` can be downcast to a type that exposes additional information
   /// about the V8 exception. By default this type is `JsError`, however it may
   /// be a different type if `RuntimeOptions::js_error_create_fn` has been set.
-  pub fn mod_evaluate(&mut self, id: ModuleId) -> Result<(), AnyError> {
+  pub fn dyn_mod_evaluate(
+    &mut self,
+    load_id: ModuleLoadId,
+    id: ModuleId,
+  ) -> Result<(), AnyError> {
+    self.shared_init();
+
+    let state_rc = Self::state(self);
+    let context = self.global_context();
+    let context1 = self.global_context();
+
+    let module_handle = state_rc
+      .borrow()
+      .modules
+      .get_info(id)
+      .expect("ModuleInfo not found")
+      .handle
+      .clone();
+
+    let status = {
+      let scope = &mut v8::HandleScope::with_context(&mut **self, context);
+      let module = module_handle.get(scope);
+      module.get_status()
+    };
+
+    if status == v8::ModuleStatus::Instantiated {
+      // IMPORTANT: Top-level-await is enabled, which means that return value
+      // of module evaluation is a promise.
+      //
+      // Because that promise is created internally by V8, when error occurs during
+      // module evaluation the promise is rejected, and since the promise has no rejection
+      // handler it will result in call to `bindings::promise_reject_callback` adding
+      // the promise to pending promise rejection table - meaning JsRuntime will return
+      // error on next poll().
+      //
+      // This situation is not desirable as we want to manually return error at the
+      // end of this function to handle it further. It means we need to manually
+      // remove this promise from pending promise rejection table.
+      //
+      // For more details see:
+      // https://github.com/denoland/deno/issues/4908
+      // https://v8.dev/features/top-level-await#module-execution-order
+      let scope = &mut v8::HandleScope::with_context(&mut **self, context1);
+      let module = v8::Local::new(scope, &module_handle);
+      let maybe_value = module.evaluate(scope);
+
+      // Update status after evaluating.
+      let status = module.get_status();
+
+      if let Some(value) = maybe_value {
+        assert!(
+          status == v8::ModuleStatus::Evaluated
+            || status == v8::ModuleStatus::Errored
+        );
+        let promise = v8::Local::<v8::Promise>::try_from(value)
+          .expect("Expected to get promise as module evaluation result");
+        let promise_id = promise.get_identity_hash();
+        let mut state = state_rc.borrow_mut();
+        state.pending_promise_exceptions.remove(&promise_id);
+        let promise_global = v8::Global::new(scope, promise);
+        let module_global = v8::Global::new(scope, module);
+        state
+          .pending_dyn_mod_evaluate
+          .insert(load_id, (id, promise_global, module_global));
+      } else {
+        assert!(status == v8::ModuleStatus::Errored);
+      }
+    }
+
+    if status == v8::ModuleStatus::Evaluated {
+      self.dyn_import_done(load_id, id)?;
+    }
+
+    Ok(())
+  }
+
+  /// Evaluates an already instantiated ES module.
+  ///
+  /// `AnyError` can be downcast to a type that exposes additional information
+  /// about the V8 exception. By default this type is `JsError`, however it may
+  /// be a different type if `RuntimeOptions::js_error_create_fn` has been set.
+  fn mod_evaluate_inner(
+    &mut self,
+    id: ModuleId,
+  ) -> Result<mpsc::Receiver<Result<(), AnyError>>, AnyError> {
     self.shared_init();
 
     let state_rc = Self::state(self);
@@ -716,6 +818,8 @@ impl JsRuntime {
       .expect("ModuleInfo not found");
     let mut status = module.get_status();
 
+    let (sender, receiver) = mpsc::channel(1);
+
     if status == v8::ModuleStatus::Instantiated {
       // IMPORTANT: Top-level-await is enabled, which means that return value
       // of module evaluation is a promise.
@@ -748,20 +852,30 @@ impl JsRuntime {
         let promise_id = promise.get_identity_hash();
         let mut state = state_rc.borrow_mut();
         state.pending_promise_exceptions.remove(&promise_id);
+        let promise_global = v8::Global::new(scope, promise);
+        state
+          .pending_mod_evaluate
+          .insert(id, (promise_global, sender));
       } else {
         assert!(status == v8::ModuleStatus::Errored);
       }
     }
 
-    match status {
-      v8::ModuleStatus::Evaluated => Ok(()),
-      v8::ModuleStatus::Errored => {
-        let exception = module.get_exception();
-        exception_to_err_result(scope, exception)
-          .map_err(|err| attach_handle_to_error(scope, err, exception))
+    Ok(receiver)
   }
-      other => panic!("Unexpected module status {:?}", other),
+
+  pub async fn mod_evaluate(&mut self, id: ModuleId) -> Result<(), AnyError> {
+    let mut receiver = self.mod_evaluate_inner(id)?;
+
+    poll_fn(|cx| {
+      if let Poll::Ready(result) = receiver.poll_next_unpin(cx) {
+        debug!("received module evaluate");
+        return Poll::Ready(result.unwrap());
       }
+      let _r = self.poll_unpin(cx)?;
+      Poll::Pending
+    })
+    .await
   }
 
   fn dyn_import_error(
@@ -922,14 +1036,121 @@ impl JsRuntime {
             // Load is done.
             let module_id = load.root_module_id.unwrap();
             self.mod_instantiate(module_id)?;
-            match self.mod_evaluate(module_id) {
-              Ok(()) => self.dyn_import_done(dyn_import_id, module_id)?,
-              Err(err) => self.dyn_import_error(dyn_import_id, err)?,
+            self.dyn_mod_evaluate(dyn_import_id, module_id)?;
+          }
+        }
+      }
+    }
+  }
+
+  fn poll_mod_evaluate(&mut self, _cx: &mut Context) -> Result<(), AnyError> {
+    let state_rc = Self::state(self);
+
+    let context = self.global_context();
+    {
+      let scope = &mut v8::HandleScope::with_context(&mut **self, context);
+
+      let mut state = state_rc.borrow_mut();
+
+      if let Some(&module_id) = state.pending_mod_evaluate.keys().next() {
+        let handle = state.pending_mod_evaluate.remove(&module_id).unwrap();
+        drop(state);
+
+        let promise = handle.0.get(scope);
+        let mut sender = handle.1.clone();
+
+        let promise_state = promise.state();
+
+        match promise_state {
+          v8::PromiseState::Pending => {
+            state_rc
+              .borrow_mut()
+              .pending_mod_evaluate
+              .insert(module_id, handle);
+            state_rc.borrow().waker.wake();
+          }
+          v8::PromiseState::Fulfilled => {
+            sender.try_send(Ok(())).unwrap();
+          }
+          v8::PromiseState::Rejected => {
+            let exception = promise.result(scope);
+            let err1 = exception_to_err_result::<()>(scope, exception)
+              .map_err(|err| attach_handle_to_error(scope, err, exception))
+              .unwrap_err();
+            sender.try_send(Err(err1)).unwrap();
+          }
+        }
+      }
     };
+
+    Ok(())
+  }
+
+  fn poll_dyn_imports_evaluate(
+    &mut self,
+    _cx: &mut Context,
+  ) -> Result<(), AnyError> {
+    let state_rc = Self::state(self);
+
+    loop {
+      let context = self.global_context();
+      let maybe_result = {
+        let scope = &mut v8::HandleScope::with_context(&mut **self, context);
+
+        let mut state = state_rc.borrow_mut();
+        if let Some(&dyn_import_id) =
+          state.pending_dyn_mod_evaluate.keys().next()
+        {
+          let handle = state
+            .pending_dyn_mod_evaluate
+            .remove(&dyn_import_id)
+            .unwrap();
+          drop(state);
+
+          let module_id = handle.0;
+          let promise = handle.1.get(scope);
+          let _module = handle.2.get(scope);
+
+          let promise_state = promise.state();
+
+          match promise_state {
+            v8::PromiseState::Pending => {
+              state_rc
+                .borrow_mut()
+                .pending_dyn_mod_evaluate
+                .insert(dyn_import_id, handle);
+              state_rc.borrow().waker.wake();
+              None
+            }
+            v8::PromiseState::Fulfilled => Some(Ok((dyn_import_id, module_id))),
+            v8::PromiseState::Rejected => {
+              let exception = promise.result(scope);
+              let err1 = exception_to_err_result::<()>(scope, exception)
+                .map_err(|err| attach_handle_to_error(scope, err, exception))
+                .unwrap_err();
+              Some(Err((dyn_import_id, err1)))
             }
           }
+        } else {
+          None
+        }
+      };
+
+      if let Some(result) = maybe_result {
+        match result {
+          Ok((dyn_import_id, module_id)) => {
+            self.dyn_import_done(dyn_import_id, module_id)?;
+          }
+          Err((dyn_import_id, err1)) => {
+            self.dyn_import_error(dyn_import_id, err1)?;
           }
         }
+      } else {
+        break;
+      }
+    }
+
+    Ok(())
   }
 
   fn register_during_load(
@@ -2003,7 +2224,7 @@ pub mod tests {
     runtime.mod_instantiate(mod_a).unwrap();
     assert_eq!(dispatch_count.load(Ordering::Relaxed), 0);
 
-    runtime.mod_evaluate(mod_a).unwrap();
+    runtime.mod_evaluate_inner(mod_a).unwrap();
     assert_eq!(dispatch_count.load(Ordering::Relaxed), 1);
   }
 
@@ -2246,7 +2467,7 @@ pub mod tests {
     )
     .unwrap();
 
-    runtime.mod_evaluate(module_id).unwrap();
+    futures::executor::block_on(runtime.mod_evaluate(module_id)).unwrap();
 
     let _snapshot = runtime.snapshot();
   }