feat(web): add beforeunload event (#14830)

This commit adds the 'beforeunload' event.

Co-authored-by: Bartek Iwańczuk <biwanczuk@gmail.com>

13 files changed, 166 insertions, 11 deletions

diff --git a/cli/lsp/testing/execution.rs b/cli/lsp/testing/execution.rs
index 6b4e947a0..83f74e5ed 100644
--- a/cli/lsp/testing/execution.rs
+++ b/cli/lsp/testing/execution.rs
@@ -226,6 +226,12 @@ async fn test_specifier(
 
     worker.js_runtime.resolve_value(test_result).await?;
 
+    loop {
+      if !worker.dispatch_beforeunload_event(&located_script_name!())? {
+        break;
+      }
+      worker.run_event_loop(false).await?;
+    }
     worker.dispatch_unload_event(&located_script_name!())?;
   }
 
diff --git a/cli/main.rs b/cli/main.rs
index e74ed8518..de44add17 100644
--- a/cli/main.rs
+++ b/cli/main.rs
@@ -639,7 +639,13 @@ async fn eval_command(
   }
   worker.execute_main_module(&main_module).await?;
   worker.dispatch_load_event(&located_script_name!())?;
-  worker.run_event_loop(false).await?;
+  loop {
+    worker.run_event_loop(false).await?;
+
+    if !worker.dispatch_beforeunload_event(&located_script_name!())? {
+      break;
+    }
+  }
   worker.dispatch_unload_event(&located_script_name!())?;
   Ok(0)
 }
@@ -975,7 +981,12 @@ async fn run_from_stdin(flags: Flags) -> Result<i32, AnyError> {
   }
   worker.execute_main_module(&main_module).await?;
   worker.dispatch_load_event(&located_script_name!())?;
-  worker.run_event_loop(false).await?;
+  loop {
+    worker.run_event_loop(false).await?;
+    if !worker.dispatch_beforeunload_event(&located_script_name!())? {
+      break;
+    }
+  }
   worker.dispatch_unload_event(&located_script_name!())?;
   Ok(worker.get_exit_code())
 }
@@ -1014,7 +1025,15 @@ async fn run_with_watch(flags: Flags, script: String) -> Result<i32, AnyError> {
       self.worker.dispatch_load_event(&located_script_name!())?;
       self.pending_unload = true;
 
-      let result = self.worker.run_event_loop(false).await;
+      let result = loop {
+        let result = self.worker.run_event_loop(false).await;
+        if !self
+          .worker
+          .dispatch_beforeunload_event(&located_script_name!())?
+        {
+          break result;
+        }
+      };
       self.pending_unload = false;
 
       if let Err(err) = result {
@@ -1162,9 +1181,16 @@ async fn run_command(
   }
 
   worker.dispatch_load_event(&located_script_name!())?;
-  worker
-    .run_event_loop(maybe_coverage_collector.is_none())
-    .await?;
+
+  loop {
+    worker
+      .run_event_loop(maybe_coverage_collector.is_none())
+      .await?;
+    if !worker.dispatch_beforeunload_event(&located_script_name!())? {
+      break;
+    }
+  }
+
   worker.dispatch_unload_event(&located_script_name!())?;
 
   if let Some(coverage_collector) = maybe_coverage_collector.as_mut() {
diff --git a/cli/standalone.rs b/cli/standalone.rs
index d66eb7694..50baf70ea 100644
--- a/cli/standalone.rs
+++ b/cli/standalone.rs
@@ -316,7 +316,14 @@ pub async fn run(
   );
   worker.execute_main_module(main_module).await?;
   worker.dispatch_load_event(&located_script_name!())?;
-  worker.run_event_loop(true).await?;
+
+  loop {
+    worker.run_event_loop(false).await?;
+    if !worker.dispatch_beforeunload_event(&located_script_name!())? {
+      break;
+    }
+  }
+
   worker.dispatch_unload_event(&located_script_name!())?;
   std::process::exit(0);
 }
diff --git a/cli/tests/integration/run_tests.rs b/cli/tests/integration/run_tests.rs
index bd27cd8dd..1cd1db0ef 100644
--- a/cli/tests/integration/run_tests.rs
+++ b/cli/tests/integration/run_tests.rs
@@ -249,6 +249,12 @@ itest!(webstorage_serialization {
   output: "webstorage/serialization.ts.out",
 });
 
+// tests the beforeunload event
+itest!(beforeunload_event {
+  args: "run before_unload.js",
+  output: "before_unload.js.out",
+});
+
 // tests to ensure that when `--location` is set, all code shares the same
 // localStorage cache based on the origin of the location URL.
 #[test]
diff --git a/cli/tests/testdata/before_unload.js b/cli/tests/testdata/before_unload.js
new file mode 100644
index 000000000..2572e512b
--- /dev/null
+++ b/cli/tests/testdata/before_unload.js
@@ -0,0 +1,21 @@
+let count = 0;
+
+console.log("0");
+
+globalThis.addEventListener("beforeunload", (e) => {
+  console.log("GOT EVENT");
+  if (count === 0 || count === 1) {
+    e.preventDefault();
+    setTimeout(() => {
+      console.log("3");
+    }, 100);
+  }
+
+  count++;
+});
+
+console.log("1");
+
+setTimeout(() => {
+  console.log("2");
+}, 100);
diff --git a/cli/tests/testdata/before_unload.js.out b/cli/tests/testdata/before_unload.js.out
new file mode 100644
index 000000000..f1f2ab49a
--- /dev/null
+++ b/cli/tests/testdata/before_unload.js.out
@@ -0,0 +1,8 @@
+0
+1
+2
+GOT EVENT
+3
+GOT EVENT
+3
+GOT EVENT
diff --git a/cli/tools/bench.rs b/cli/tools/bench.rs
index 3c40b4e95..3a40a4e97 100644
--- a/cli/tools/bench.rs
+++ b/cli/tools/bench.rs
@@ -404,6 +404,12 @@ async fn bench_specifier(
 
   worker.js_runtime.resolve_value(bench_result).await?;
 
+  loop {
+    if !worker.dispatch_beforeunload_event(&located_script_name!())? {
+      break;
+    }
+    worker.run_event_loop(false).await?;
+  }
   worker.dispatch_unload_event(&located_script_name!())?;
 
   Ok(())
diff --git a/cli/tools/test.rs b/cli/tools/test.rs
index ac146fdbf..71374d94e 100644
--- a/cli/tools/test.rs
+++ b/cli/tools/test.rs
@@ -814,6 +814,13 @@ async fn test_specifier(
 
   worker.js_runtime.resolve_value(test_result).await?;
 
+  loop {
+    if !worker.dispatch_beforeunload_event(&located_script_name!())? {
+      break;
+    }
+    worker.run_event_loop(false).await?;
+  }
+
   worker.dispatch_unload_event(&located_script_name!())?;
 
   if let Some(coverage_collector) = maybe_coverage_collector.as_mut() {
diff --git a/core/01_core.js b/core/01_core.js
index 9337c0231..156300327 100644
--- a/core/01_core.js
+++ b/core/01_core.js
@@ -267,6 +267,7 @@
     destructureError: opSync.bind(null, "op_destructure_error"),
     terminate: opSync.bind(null, "op_terminate"),
     opNames: opSync.bind(null, "op_op_names"),
+    eventLoopHasMoreWork: opSync.bind(null, "op_event_loop_has_more_work"),
   });
 
   ObjectAssign(globalThis.__bootstrap, { core });
diff --git a/core/ops_builtin_v8.rs b/core/ops_builtin_v8.rs
index 7f0c58212..4bc80faa5 100644
--- a/core/ops_builtin_v8.rs
+++ b/core/ops_builtin_v8.rs
@@ -47,6 +47,7 @@ pub(crate) fn init_builtins_v8() -> Vec<OpDecl> {
     op_op_names::decl(),
     op_apply_source_map::decl(),
     op_set_format_exception_callback::decl(),
+    op_event_loop_has_more_work::decl(),
   ]
 }
 
@@ -786,3 +787,26 @@ fn op_set_format_exception_callback<'a>(
   let old = old.map(|v| v8::Local::new(scope, v));
   Ok(old.map(|v| from_v8(scope, v.into()).unwrap()))
 }
+
+#[op(v8)]
+fn op_event_loop_has_more_work(scope: &mut v8::HandleScope) -> bool {
+  let state_rc = JsRuntime::state(scope);
+  let module_map_rc = JsRuntime::module_map(scope);
+  let state = state_rc.borrow_mut();
+  let module_map = module_map_rc.borrow();
+
+  let has_pending_refed_ops = state.pending_ops.len() > state.unrefed_ops.len();
+  let has_pending_dyn_imports = module_map.has_pending_dynamic_imports();
+  let has_pending_dyn_module_evaluation =
+    !state.pending_dyn_mod_evaluate.is_empty();
+  let has_pending_module_evaluation = state.pending_mod_evaluate.is_some();
+  let has_pending_background_tasks = scope.has_pending_background_tasks();
+  let has_tick_scheduled = state.has_tick_scheduled;
+
+  has_pending_refed_ops
+    || has_pending_dyn_imports
+    || has_pending_dyn_module_evaluation
+    || has_pending_module_evaluation
+    || has_pending_background_tasks
+    || has_tick_scheduled
+}
diff --git a/core/runtime.rs b/core/runtime.rs
index 23fe73013..8b150e4e9 100644
--- a/core/runtime.rs
+++ b/core/runtime.rs
@@ -90,14 +90,14 @@ pub struct JsRuntime {
   event_loop_middlewares: Vec<Box<OpEventLoopFn>>,
 }
 
-struct DynImportModEvaluate {
+pub(crate) struct DynImportModEvaluate {
   load_id: ModuleLoadId,
   module_id: ModuleId,
   promise: v8::Global<v8::Promise>,
   module: v8::Global<v8::Module>,
 }
 
-struct ModEvaluate {
+pub(crate) struct ModEvaluate {
   promise: v8::Global<v8::Promise>,
   sender: oneshot::Sender<Result<(), Error>>,
 }
@@ -158,8 +158,8 @@ pub(crate) struct JsRuntimeState {
   pub(crate) js_wasm_streaming_cb: Option<v8::Global<v8::Function>>,
   pub(crate) pending_promise_exceptions:
     HashMap<v8::Global<v8::Promise>, v8::Global<v8::Value>>,
-  pending_dyn_mod_evaluate: Vec<DynImportModEvaluate>,
-  pending_mod_evaluate: Option<ModEvaluate>,
+  pub(crate) pending_dyn_mod_evaluate: Vec<DynImportModEvaluate>,
+  pub(crate) pending_mod_evaluate: Option<ModEvaluate>,
   /// A counter used to delay our dynamic import deadlock detection by one spin
   /// of the event loop.
   dyn_module_evaluate_idle_counter: u32,
@@ -1021,6 +1021,30 @@ Pending dynamic modules:\n".to_string();
 
     Poll::Pending
   }
+
+  pub fn event_loop_has_work(&mut self) -> bool {
+    let state_rc = Self::state(self.v8_isolate());
+    let module_map_rc = Self::module_map(self.v8_isolate());
+    let state = state_rc.borrow_mut();
+    let module_map = module_map_rc.borrow();
+
+    let has_pending_refed_ops =
+      state.pending_ops.len() > state.unrefed_ops.len();
+    let has_pending_dyn_imports = module_map.has_pending_dynamic_imports();
+    let has_pending_dyn_module_evaluation =
+      !state.pending_dyn_mod_evaluate.is_empty();
+    let has_pending_module_evaluation = state.pending_mod_evaluate.is_some();
+    let has_pending_background_tasks =
+      self.v8_isolate().has_pending_background_tasks();
+    let has_tick_scheduled = state.has_tick_scheduled;
+
+    has_pending_refed_ops
+      || has_pending_dyn_imports
+      || has_pending_dyn_module_evaluation
+      || has_pending_module_evaluation
+      || has_pending_background_tasks
+      || has_tick_scheduled
+  }
 }
 
 extern "C" fn near_heap_limit_callback<F>(
diff --git a/runtime/js/99_main.js b/runtime/js/99_main.js
index 1d046d161..c13faa936 100644
--- a/runtime/js/99_main.js
+++ b/runtime/js/99_main.js
@@ -583,6 +583,7 @@ delete Intl.v8BreakIterator;
 
     defineEventHandler(window, "error");
     defineEventHandler(window, "load");
+    defineEventHandler(window, "beforeunload");
     defineEventHandler(window, "unload");
     const isUnloadDispatched = SymbolFor("isUnloadDispatched");
     // Stores the flag for checking whether unload is dispatched or not.
diff --git a/runtime/worker.rs b/runtime/worker.rs
index acb50dc30..fd937559f 100644
--- a/runtime/worker.rs
+++ b/runtime/worker.rs
@@ -371,6 +371,24 @@ impl MainWorker {
       "dispatchEvent(new Event('unload'))",
     )
   }
+
+  /// Dispatches "beforeunload" event to the JavaScript runtime. Returns a boolean
+  /// indicating if the event was prevented and thus event loop should continue
+  /// running.
+  pub fn dispatch_beforeunload_event(
+    &mut self,
+    script_name: &str,
+  ) -> Result<bool, AnyError> {
+    let value = self.js_runtime.execute_script(
+      script_name,
+      // NOTE(@bartlomieju): not using `globalThis` here, because user might delete
+      // it. Instead we're using global `dispatchEvent` function which will
+      // used a saved reference to global scope.
+      "dispatchEvent(new Event('beforeunload', { cancelable: true }));",
+    )?;
+    let local_value = value.open(&mut self.js_runtime.handle_scope());
+    Ok(local_value.is_false())
+  }
 }
 
 #[cfg(test)]