Support dynamic import (#136)

src/binding.cc

@@ -8,6 +8,8 @@
 #include "v8/include/v8-platform.h"
 #include "v8/include/v8.h"
 
+const uint32_t kSlotDynamicImport = 1000;
+
 using namespace support;
 
 static_assert(sizeof(v8::ScriptOrigin) == sizeof(size_t) * 7,
@@ -39,6 +41,27 @@ static_assert(sizeof(v8::Location) == sizeof(size_t) * 1,
 static_assert(sizeof(v8::SnapshotCreator) == sizeof(size_t) * 1,
               "SnapshotCreator size mismatch");
 
+// This is an extern C calling convention compatible version of
+// v8::HostImportModuleDynamicallyCallback
+typedef v8::Promise* (*v8__HostImportModuleDynamicallyCallback)(
+    v8::Local<v8::Context> context, v8::Local<v8::ScriptOrModule> referrer,
+    v8::Local<v8::String> specifier);
+
+v8::MaybeLocal<v8::Promise> HostImportModuleDynamicallyCallback(
+    v8::Local<v8::Context> context, v8::Local<v8::ScriptOrModule> referrer,
+    v8::Local<v8::String> specifier) {
+  auto* isolate = context->GetIsolate();
+  auto* callback = reinterpret_cast<v8__HostImportModuleDynamicallyCallback>(
+      isolate->GetData(kSlotDynamicImport));
+  assert(callback != nullptr);
+  auto* promise_ptr = callback(context, referrer, specifier);
+  if (promise_ptr == nullptr) {
+    return v8::MaybeLocal<v8::Promise>();
+  } else {
+    return v8::MaybeLocal<v8::Promise>(ptr_to_local(promise_ptr));
+  }
+}
+
 extern "C" {
 
 void v8__V8__SetFlagsFromCommandLine(int* argc, char** argv) {
@@ -102,6 +125,13 @@ void v8__Isolate__SetHostInitializeImportMetaObjectCallback(
   isolate->SetHostInitializeImportMetaObjectCallback(callback);
 }
 
+void v8__Isolate__SetHostImportModuleDynamicallyCallback(
+    v8::Isolate* isolate, v8__HostImportModuleDynamicallyCallback callback) {
+  isolate->SetData(kSlotDynamicImport, reinterpret_cast<void*>(callback));
+  isolate->SetHostImportModuleDynamicallyCallback(
+      HostImportModuleDynamicallyCallback);
+}
+
 bool v8__Isolate__AddMessageListener(v8::Isolate& isolate,
                                      v8::MessageCallback callback) {
   return isolate.AddMessageListener(callback);
@@ -546,8 +576,10 @@ void v8__TryCatch__SetCaptureMessage(v8::TryCatch& self, bool value) {
   self.SetCaptureMessage(value);
 }
 
-v8::Uint8Array* v8__Uint8Array__New(v8::ArrayBuffer* buf_ptr, size_t byte_offset, size_t length) {
-  return local_to_ptr(v8::Uint8Array::New(ptr_to_local(buf_ptr), byte_offset, length));
+v8::Uint8Array* v8__Uint8Array__New(v8::ArrayBuffer* buf_ptr,
+                                    size_t byte_offset, size_t length) {
+  return local_to_ptr(
+      v8::Uint8Array::New(ptr_to_local(buf_ptr), byte_offset, length));
 }
 
 v8::Script* v8__Script__Compile(v8::Context* context, v8::String* source,

src/isolate.rs

@@ -9,20 +9,55 @@ use crate::Local;
 use crate::Message;
 use crate::Module;
 use crate::Object;
+use crate::Promise;
+use crate::ScriptOrModule;
 use crate::StartupData;
+use crate::String;
 use crate::Value;
 use std::ffi::c_void;
 use std::ops::Deref;
 use std::ops::DerefMut;
 use std::ptr::NonNull;
 
-type MessageCallback = extern "C" fn(Local<Message>, Local<Value>);
+pub type MessageCallback = extern "C" fn(Local<Message>, Local<Value>);
 
-type PromiseRejectCallback = extern "C" fn(PromiseRejectMessage);
+pub type PromiseRejectCallback = extern "C" fn(PromiseRejectMessage);
 
-type HostInitializeImportMetaObjectCallback =
+/// HostInitializeImportMetaObjectCallback is called the first time import.meta
+/// is accessed for a module. Subsequent access will reuse the same value.
+///
+/// The method combines two implementation-defined abstract operations into one:
+/// HostGetImportMetaProperties and HostFinalizeImportMeta.
+///
+/// The embedder should use v8::Object::CreateDataProperty to add properties on
+/// the meta object.
+pub type HostInitializeImportMetaObjectCallback =
   extern "C" fn(Local<Context>, Local<Module>, Local<Object>);
 
+/// HostImportModuleDynamicallyCallback is called when we require the
+/// embedder to load a module. This is used as part of the dynamic
+/// import syntax.
+///
+/// The referrer contains metadata about the script/module that calls
+/// import.
+///
+/// The specifier is the name of the module that should be imported.
+///
+/// The embedder must compile, instantiate, evaluate the Module, and
+/// obtain it's namespace object.
+///
+/// The Promise returned from this function is forwarded to userland
+/// JavaScript. The embedder must resolve this promise with the module
+/// namespace object. In case of an exception, the embedder must reject
+/// this promise with the exception. If the promise creation itself
+/// fails (e.g. due to stack overflow), the embedder must propagate
+/// that exception by returning an empty MaybeLocal.
+pub type HostImportModuleDynamicallyCallback = extern "C" fn(
+  Local<Context>,
+  Local<ScriptOrModule>,
+  Local<String>,
+) -> *mut Promise;
+
 extern "C" {
   fn v8__Isolate__New(params: *mut CreateParams) -> *mut Isolate;
   fn v8__Isolate__Dispose(this: *mut Isolate);
@@ -48,6 +83,10 @@ extern "C" {
     isolate: *mut Isolate,
     callback: HostInitializeImportMetaObjectCallback,
   );
+  fn v8__Isolate__SetHostImportModuleDynamicallyCallback(
+    isolate: *mut Isolate,
+    callback: HostImportModuleDynamicallyCallback,
+  );
   fn v8__Isolate__ThrowException(
     isolate: &Isolate,
     exception: &Value,
@@ -174,6 +213,17 @@ impl Isolate {
     }
   }
 
+  /// This specifies the callback called by the upcoming dynamic
+  /// import() language feature to load modules.
+  pub fn set_host_import_module_dynamically_callback(
+    &mut self,
+    callback: HostImportModuleDynamicallyCallback,
+  ) {
+    unsafe {
+      v8__Isolate__SetHostImportModuleDynamicallyCallback(self, callback)
+    }
+  }
+
   /// Schedules an exception to be thrown when returning to JavaScript. When an
   /// exception has been scheduled it is illegal to invoke any JavaScript
   /// operation; the caller must return immediately and only after the exception

src/lib.rs

@@ -55,7 +55,7 @@ pub use function::{
 };
 pub use global::Global;
 pub use handle_scope::{EscapableHandleScope, HandleScope, ToLocal};
-pub use isolate::{InIsolate, Isolate, OwnedIsolate};
+pub use isolate::*;
 pub use local::Local;
 pub use locker::Locker;
 pub use module::*;

tests/test_api.rs

@@ -5,6 +5,7 @@ extern crate lazy_static;
 
 use rusty_v8 as v8;
 use rusty_v8::{new_null, FunctionCallbackInfo, InIsolate, Local, ToLocal};
+use std::sync::atomic::{AtomicUsize, Ordering};
 use std::sync::Mutex;
 
 lazy_static! {
@@ -339,7 +340,6 @@ fn add_message_listener() {
   let mut isolate = v8::Isolate::new(params);
   isolate.set_capture_stack_trace_for_uncaught_exceptions(true, 32);
 
-  use std::sync::atomic::{AtomicUsize, Ordering};
   static CALL_COUNT: AtomicUsize = AtomicUsize::new(0);
 
   extern "C" fn check_message_0(
@@ -389,7 +389,6 @@ fn set_host_initialize_import_meta_object_callback() {
   params.set_array_buffer_allocator(v8::new_default_allocator());
   let mut isolate = v8::Isolate::new(params);
 
-  use std::sync::atomic::{AtomicUsize, Ordering};
   static CALL_COUNT: AtomicUsize = AtomicUsize::new(0);
 
   extern "C" fn callback(
@@ -791,25 +790,6 @@ fn promise_rejected() {
   drop(locker);
 }
 
-extern "C" fn fn_callback(info: &FunctionCallbackInfo) {
-  assert_eq!(info.length(), 0);
-  {
-    let rv = &mut info.get_return_value();
-    #[allow(mutable_transmutes)]
-    #[allow(clippy::transmute_ptr_to_ptr)]
-    let info: &mut FunctionCallbackInfo = unsafe { std::mem::transmute(info) };
-    {
-      let mut hs = v8::HandleScope::new(info);
-      let scope = hs.enter();
-      let s = v8::String::new(scope, "Hello callback!").unwrap();
-      let value: Local<v8::Value> = s.into();
-      let rv_value = rv.get(scope);
-      assert!(rv_value.is_undefined());
-      rv.set(value);
-    }
-  }
-}
-
 #[test]
 fn function() {
   setup();
@@ -817,6 +797,27 @@ fn function() {
   params.set_array_buffer_allocator(v8::new_default_allocator());
   let isolate = v8::Isolate::new(params);
   let mut locker = v8::Locker::new(&isolate);
+
+  extern "C" fn fn_callback(info: &FunctionCallbackInfo) {
+    assert_eq!(info.length(), 0);
+    {
+      let rv = &mut info.get_return_value();
+      #[allow(mutable_transmutes)]
+      #[allow(clippy::transmute_ptr_to_ptr)]
+      let info: &mut FunctionCallbackInfo =
+        unsafe { std::mem::transmute(info) };
+      {
+        let mut hs = v8::HandleScope::new(info);
+        let scope = hs.enter();
+        let s = v8::String::new(scope, "Hello callback!").unwrap();
+        let value: Local<v8::Value> = s.into();
+        let rv_value = rv.get(scope);
+        assert!(rv_value.is_undefined());
+        rv.set(value);
+      }
+    }
+  }
+
   {
     let mut hs = v8::HandleScope::new(&mut locker);
     let scope = hs.enter();
@@ -1305,3 +1306,53 @@ fn uint8_array() {
   isolate.exit();
   drop(g);
 }
+
+#[test]
+fn dynamic_import() {
+  let g = setup();
+  let mut params = v8::Isolate::create_params();
+  params.set_array_buffer_allocator(v8::new_default_allocator());
+  let mut isolate = v8::Isolate::new(params);
+
+  static CALL_COUNT: AtomicUsize = AtomicUsize::new(0);
+
+  extern "C" fn dynamic_import_cb(
+    context: v8::Local<v8::Context>,
+    _referrer: v8::Local<v8::ScriptOrModule>,
+    specifier: v8::Local<v8::String>,
+  ) -> *mut v8::Promise {
+    let mut cbs = v8::CallbackScope::new(context);
+    let mut hs = v8::HandleScope::new(cbs.enter());
+    let scope = hs.enter();
+    assert!(specifier.strict_equals(v8_str(scope, "bar.js").into()));
+    let e = v8_str(scope, "boom");
+    scope.isolate().throw_exception(e.into());
+    CALL_COUNT.fetch_add(1, Ordering::SeqCst);
+    std::ptr::null_mut()
+  }
+  isolate.set_host_import_module_dynamically_callback(dynamic_import_cb);
+
+  isolate.enter();
+  let mut locker = v8::Locker::new(&isolate);
+  {
+    let mut hs = v8::HandleScope::new(&mut locker);
+    let s = hs.enter();
+    let mut context = v8::Context::new(s);
+    context.enter();
+
+    let result = eval(
+      s,
+      context,
+      "(async function () {\n\
+       let x = await import('bar.js');\n\
+       })();",
+    );
+    assert!(result.is_some());
+    assert_eq!(CALL_COUNT.load(Ordering::SeqCst), 1);
+
+    context.exit();
+  }
+  drop(locker);
+  isolate.exit();
+  drop(g);
+}