refactor(core): JsRuntime is not a Future (#7855)

This commit rewrites deno_core::JsRuntime to not implement Future
trait.

Instead there are two separate methods:
- JsRuntime::poll_event_loop() - does single tick of event loop
- JsRuntime::run_event_loop() - runs event loop to completion

cli/worker.rs

@@ -240,7 +240,7 @@ impl Future for Worker {
     // We always poll the inspector if it exists.
     let _ = inner.inspector.as_mut().map(|i| i.poll_unpin(cx));
     inner.waker.register(cx.waker());
-    inner.js_runtime.poll_unpin(cx)
+    inner.js_runtime.poll_event_loop(cx)
   }
 }
 

core/README.md

@@ -9,9 +9,12 @@ bindings.
 
 This Rust crate contains the essential V8 bindings for Deno's command-line
 interface (Deno CLI). The main abstraction here is the JsRuntime which provides
-a way to execute JavaScript. The JsRuntime is modeled as a
-`Future<Item=(), Error=JsError>` which completes once all of its ops have
-completed.
+a way to execute JavaScript.
+
+The JsRuntime implements an event loop abstraction for the executed code that
+keeps track of all pending tasks (async ops, dynamic module loads). It is user's
+responsibility to drive that loop by using `JsRuntime::run_event_loop` method -
+it must be executed in the context of Rust's future executor (eg. tokio, smol).
 
 In order to bind Rust functions into JavaScript, use the `Deno.core.dispatch()`
 function to trigger the "dispatch" callback in Rust. The user is responsible for

core/examples/http_bench_bin_ops.rs

@@ -260,7 +260,7 @@ fn main() {
         include_str!("http_bench_bin_ops.js"),
       )
       .unwrap();
-    js_runtime.await
+    js_runtime.run_event_loop().await
   };
   runtime.block_on(future).unwrap();
 }

core/examples/http_bench_json_ops.rs

@@ -193,7 +193,7 @@ fn main() {
         include_str!("http_bench_json_ops.js"),
       )
       .unwrap();
-    js_runtime.await
+    js_runtime.run_event_loop().await
   };
   runtime.block_on(future).unwrap();
 }

core/runtime.rs

@@ -453,55 +453,51 @@ impl JsRuntime {
         .remove_near_heap_limit_callback(cb, heap_limit);
     }
   }
+
+  /// Runs event loop to completion
+  ///
+  /// This future resolves when:
+  ///  - there are no more pending dynamic imports
+  ///  - there are no more pending ops
+  pub async fn run_event_loop(&mut self) -> Result<(), AnyError> {
+    poll_fn(|cx| self.poll_event_loop(cx)).await
   }
 
-extern "C" fn near_heap_limit_callback<F>(
-  data: *mut c_void,
-  current_heap_limit: usize,
-  initial_heap_limit: usize,
-) -> usize
-where
-  F: FnMut(usize, usize) -> usize,
-{
-  let callback = unsafe { &mut *(data as *mut F) };
-  callback(current_heap_limit, initial_heap_limit)
-}
+  /// Runs a single tick of event loop
+  pub fn poll_event_loop(
+    &mut self,
+    cx: &mut Context,
+  ) -> Poll<Result<(), AnyError>> {
+    self.shared_init();
 
-impl Future for JsRuntime {
-  type Output = Result<(), AnyError>;
-
-  fn poll(self: Pin<&mut Self>, cx: &mut Context) -> Poll<Self::Output> {
-    let runtime = self.get_mut();
-    runtime.shared_init();
-
-    let state_rc = Self::state(runtime.v8_isolate());
+    let state_rc = Self::state(self.v8_isolate());
     {
       let state = state_rc.borrow();
       state.waker.register(cx.waker());
     }
 
     // Top level modules
-    runtime.poll_mod_evaluate(cx)?;
+    self.evaluate_pending_modules()?;
 
     // Dynamic module loading - ie. modules loaded using "import()"
     {
-      let poll_imports = runtime.prepare_dyn_imports(cx)?;
+      let poll_imports = self.prepare_dyn_imports(cx)?;
       assert!(poll_imports.is_ready());
 
-      let poll_imports = runtime.poll_dyn_imports(cx)?;
+      let poll_imports = self.poll_dyn_imports(cx)?;
       assert!(poll_imports.is_ready());
 
-      runtime.poll_dyn_imports_evaluate(cx)?;
+      self.evaluate_dyn_imports()?;
 
-      runtime.check_promise_exceptions()?;
+      self.check_promise_exceptions()?;
     }
 
     // Ops
     {
-      let overflow_response = runtime.poll_pending_ops(cx);
-      runtime.async_op_response(overflow_response)?;
-      runtime.drain_macrotasks()?;
-      runtime.check_promise_exceptions()?;
+      let overflow_response = self.poll_pending_ops(cx);
+      self.async_op_response(overflow_response)?;
+      self.drain_macrotasks()?;
+      self.check_promise_exceptions()?;
     }
 
     let state = state_rc.borrow();
@@ -527,6 +523,18 @@ impl Future for JsRuntime {
   }
 }
 
+extern "C" fn near_heap_limit_callback<F>(
+  data: *mut c_void,
+  current_heap_limit: usize,
+  initial_heap_limit: usize,
+) -> usize
+where
+  F: FnMut(usize, usize) -> usize,
+{
+  let callback = unsafe { &mut *(data as *mut F) };
+  callback(current_heap_limit, initial_heap_limit)
+}
+
 impl JsRuntimeState {
   // Called by V8 during `Isolate::mod_instantiate`.
   pub fn module_resolve_cb(
@@ -859,7 +867,7 @@ impl JsRuntime {
         debug!("received module evaluate");
         return Poll::Ready(result.unwrap());
       }
-      let _r = self.poll_unpin(cx)?;
+      let _r = self.poll_event_loop(cx)?;
       Poll::Pending
     })
     .await
@@ -1030,7 +1038,7 @@ impl JsRuntime {
     }
   }
 
-  fn poll_mod_evaluate(&mut self, _cx: &mut Context) -> Result<(), AnyError> {
+  fn evaluate_pending_modules(&mut self) -> Result<(), AnyError> {
     let state_rc = Self::state(self.v8_isolate());
 
     let context = self.global_context();
@@ -1074,10 +1082,7 @@ impl JsRuntime {
     Ok(())
   }
 
-  fn poll_dyn_imports_evaluate(
-    &mut self,
-    _cx: &mut Context,
-  ) -> Result<(), AnyError> {
+  fn evaluate_dyn_imports(&mut self) -> Result<(), AnyError> {
     let state_rc = Self::state(self.v8_isolate());
 
     loop {
@@ -1440,13 +1445,13 @@ pub mod tests {
     futures::executor::block_on(lazy(move |cx| f(cx)));
   }
 
-  fn poll_until_ready<F>(future: &mut F, max_poll_count: usize) -> F::Output
-  where
-    F: Future + Unpin,
-  {
+  fn poll_until_ready(
+    runtime: &mut JsRuntime,
+    max_poll_count: usize,
+  ) -> Result<(), AnyError> {
     let mut cx = Context::from_waker(futures::task::noop_waker_ref());
     for _ in 0..max_poll_count {
-      match future.poll_unpin(&mut cx) {
+      match runtime.poll_event_loop(&mut cx) {
         Poll::Pending => continue,
         Poll::Ready(val) => return val,
       }
@@ -1662,7 +1667,7 @@ pub mod tests {
         )
         .unwrap();
       assert_eq!(dispatch_count.load(Ordering::Relaxed), 1);
-      assert!(matches!(runtime.poll_unpin(cx), Poll::Ready(Ok(_))));
+      assert!(matches!(runtime.poll_event_loop(cx), Poll::Ready(Ok(_))));
       assert_eq!(dispatch_count.load(Ordering::Relaxed), 1);
       runtime
         .execute(
@@ -1675,11 +1680,11 @@ pub mod tests {
         )
         .unwrap();
       assert_eq!(dispatch_count.load(Ordering::Relaxed), 2);
-      assert!(matches!(runtime.poll_unpin(cx), Poll::Ready(Ok(_))));
+      assert!(matches!(runtime.poll_event_loop(cx), Poll::Ready(Ok(_))));
       runtime.execute("check3.js", "assert(nrecv == 2)").unwrap();
       assert_eq!(dispatch_count.load(Ordering::Relaxed), 2);
       // We are idle, so the next poll should be the last.
-      assert!(matches!(runtime.poll_unpin(cx), Poll::Ready(Ok(_))));
+      assert!(matches!(runtime.poll_event_loop(cx), Poll::Ready(Ok(_))));
     });
   }
 
@@ -1703,7 +1708,7 @@ pub mod tests {
       assert_eq!(dispatch_count.load(Ordering::Relaxed), 1);
       // The above op never finish, but runtime can finish
       // because the op is an unreffed async op.
-      assert!(matches!(runtime.poll_unpin(cx), Poll::Ready(Ok(_))));
+      assert!(matches!(runtime.poll_event_loop(cx), Poll::Ready(Ok(_))));
     })
   }
 
@@ -1833,7 +1838,7 @@ pub mod tests {
         )
         .unwrap();
       assert_eq!(dispatch_count.load(Ordering::Relaxed), 1);
-      assert!(matches!(runtime.poll_unpin(cx), Poll::Ready(Ok(_))));
+      assert!(matches!(runtime.poll_event_loop(cx), Poll::Ready(Ok(_))));
       runtime
         .execute("check.js", "assert(asyncRecv == 1);")
         .unwrap();
@@ -1925,7 +1930,7 @@ pub mod tests {
          "#,
         )
         .unwrap();
-      if let Poll::Ready(Err(_)) = runtime.poll_unpin(&mut cx) {
+      if let Poll::Ready(Err(_)) = runtime.poll_event_loop(&mut cx) {
         unreachable!();
       }
     });
@@ -1938,7 +1943,7 @@ pub mod tests {
       runtime
         .execute("core_test.js", include_str!("core_test.js"))
         .unwrap();
-      if let Poll::Ready(Err(_)) = runtime.poll_unpin(&mut cx) {
+      if let Poll::Ready(Err(_)) = runtime.poll_event_loop(&mut cx) {
         unreachable!();
       }
     });
@@ -1964,7 +1969,7 @@ pub mod tests {
           include_str!("encode_decode_test.js"),
         )
         .unwrap();
-      if let Poll::Ready(Err(_)) = runtime.poll_unpin(&mut cx) {
+      if let Poll::Ready(Err(_)) = runtime.poll_event_loop(&mut cx) {
         unreachable!();
       }
     });
@@ -2272,7 +2277,7 @@ pub mod tests {
 
       assert_eq!(count.load(Ordering::Relaxed), 0);
       // We should get an error here.
-      let result = runtime.poll_unpin(cx);
+      let result = runtime.poll_event_loop(cx);
       if let Poll::Ready(Ok(_)) = result {
         unreachable!();
       }
@@ -2365,14 +2370,14 @@ pub mod tests {
         .unwrap();
 
       // First poll runs `prepare_load` hook.
-      assert!(matches!(runtime.poll_unpin(cx), Poll::Pending));
+      assert!(matches!(runtime.poll_event_loop(cx), Poll::Pending));
       assert_eq!(prepare_load_count.load(Ordering::Relaxed), 1);
 
       // Second poll actually loads modules into the isolate.
-      assert!(matches!(runtime.poll_unpin(cx), Poll::Ready(Ok(_))));
+      assert!(matches!(runtime.poll_event_loop(cx), Poll::Ready(Ok(_))));
       assert_eq!(resolve_count.load(Ordering::Relaxed), 4);
       assert_eq!(load_count.load(Ordering::Relaxed), 2);
-      assert!(matches!(runtime.poll_unpin(cx), Poll::Ready(Ok(_))));
+      assert!(matches!(runtime.poll_event_loop(cx), Poll::Ready(Ok(_))));
       assert_eq!(resolve_count.load(Ordering::Relaxed), 4);
       assert_eq!(load_count.load(Ordering::Relaxed), 2);
     })
@@ -2404,10 +2409,10 @@ pub mod tests {
         )
         .unwrap();
       // First poll runs `prepare_load` hook.
-      let _ = runtime.poll_unpin(cx);
+      let _ = runtime.poll_event_loop(cx);
       assert_eq!(prepare_load_count.load(Ordering::Relaxed), 1);
       // Second poll triggers error
-      let _ = runtime.poll_unpin(cx);
+      let _ = runtime.poll_event_loop(cx);
     })
   }
 
@@ -2538,7 +2543,7 @@ main();
     at async error_async_stack.js:10:5
 "#;
 
-      match runtime.poll_unpin(cx) {
+      match runtime.poll_event_loop(cx) {
         Poll::Ready(Err(e)) => {
           assert_eq!(e.to_string(), expected_error);
         }

op_crates/web/lib.rs

@@ -75,7 +75,6 @@ pub fn get_declaration() -> PathBuf {
 mod tests {
   use deno_core::JsRuntime;
   use futures::future::lazy;
-  use futures::future::FutureExt;
   use futures::task::Context;
   use futures::task::Poll;
 
@@ -102,7 +101,7 @@ mod tests {
           include_str!("abort_controller_test.js"),
         )
         .unwrap();
-      if let Poll::Ready(Err(_)) = isolate.poll_unpin(&mut cx) {
+      if let Poll::Ready(Err(_)) = isolate.poll_event_loop(&mut cx) {
         unreachable!();
       }
     });
@@ -115,7 +114,7 @@ mod tests {
       isolate
         .execute("event_test.js", include_str!("event_test.js"))
         .unwrap();
-      if let Poll::Ready(Err(_)) = isolate.poll_unpin(&mut cx) {
+      if let Poll::Ready(Err(_)) = isolate.poll_event_loop(&mut cx) {
         unreachable!();
       }
     });
@@ -134,7 +133,7 @@ mod tests {
       } else {
         unreachable!();
       }
-      if let Poll::Ready(Err(_)) = isolate.poll_unpin(&mut cx) {
+      if let Poll::Ready(Err(_)) = isolate.poll_event_loop(&mut cx) {
         unreachable!();
       }
     });
@@ -147,7 +146,7 @@ mod tests {
       isolate
         .execute("event_target_test.js", include_str!("event_target_test.js"))
         .unwrap();
-      if let Poll::Ready(Err(_)) = isolate.poll_unpin(&mut cx) {
+      if let Poll::Ready(Err(_)) = isolate.poll_event_loop(&mut cx) {
         unreachable!();
       }
     });
@@ -163,7 +162,7 @@ mod tests {
           include_str!("text_encoding_test.js"),
         )
         .unwrap();
-      if let Poll::Ready(Err(_)) = isolate.poll_unpin(&mut cx) {
+      if let Poll::Ready(Err(_)) = isolate.poll_event_loop(&mut cx) {
         unreachable!();
       }
     });