feat(napi): support async class factory (#1779)

- Close https://github.com/napi-rs/napi-rs/issues/1777

crates/backend/src/codegen/fn.rs

@@ -112,8 +112,15 @@ impl TryToTokens for NapiFn {
       }
     };
 
+    // async factory only
+    let use_after_async = if self.is_async && self.parent.is_some() && self.fn_self.is_none() {
+      quote! { true }
+    } else {
+      quote! { false }
+    };
+
     let function_call_inner = quote! {
-      napi::bindgen_prelude::CallbackInfo::<#args_len>::new(env, cb, None).and_then(|mut cb| {
+      napi::bindgen_prelude::CallbackInfo::<#args_len>::new(env, cb, None, #use_after_async).and_then(|mut cb| {
           #build_ref_container
           #(#arg_conversions)*
           #native_call
@@ -511,6 +518,8 @@ impl NapiFn {
         if self.is_ret_result {
           if self.parent_is_generator {
             quote! { cb.generator_factory(#js_name, #ret?) }
+          } else if self.is_async {
+            quote! { cb.factory(#js_name, #ret) }
           } else {
             quote! { cb.factory(#js_name, #ret?) }
           }

crates/backend/src/codegen/struct.rs

@@ -250,7 +250,7 @@ impl NapiStruct {
         env: napi::bindgen_prelude::sys::napi_env,
         cb: napi::bindgen_prelude::sys::napi_callback_info
       ) -> napi::bindgen_prelude::sys::napi_value {
-        napi::bindgen_prelude::CallbackInfo::<#fields_len>::new(env, cb, None)
+        napi::bindgen_prelude::CallbackInfo::<#fields_len>::new(env, cb, None, false)
           .and_then(|cb| #constructor)
           .unwrap_or_else(|e| {
             unsafe { napi::bindgen_prelude::JsError::from(e).throw_into(env) };
@@ -669,7 +669,7 @@ impl NapiStruct {
               env: napi::bindgen_prelude::sys::napi_env,
               cb: napi::bindgen_prelude::sys::napi_callback_info
             ) -> napi::bindgen_prelude::sys::napi_value {
-              napi::bindgen_prelude::CallbackInfo::<0>::new(env, cb, Some(0))
+              napi::bindgen_prelude::CallbackInfo::<0>::new(env, cb, Some(0), false)
                 .and_then(|mut cb| unsafe { cb.unwrap_borrow_mut::<#struct_name>() })
                 .and_then(|obj| {
                   #to_napi_value_convert
@@ -691,7 +691,7 @@ impl NapiStruct {
               env: napi::bindgen_prelude::sys::napi_env,
               cb: napi::bindgen_prelude::sys::napi_callback_info
             ) -> napi::bindgen_prelude::sys::napi_value {
-              napi::bindgen_prelude::CallbackInfo::<1>::new(env, cb, Some(1))
+              napi::bindgen_prelude::CallbackInfo::<1>::new(env, cb, Some(1), false)
                 .and_then(|mut cb_info| unsafe {
                   cb_info.unwrap_borrow_mut::<#struct_name>()
                     .and_then(|obj| {

crates/backend/src/typegen/fn.rs

@@ -226,7 +226,14 @@ impl NapiFn {
       FnKind::Factory => self
         .parent
         .clone()
-        .map(|i| format!(": {}", i.to_string().to_case(Case::Pascal)))
+        .map(|i| {
+          let parent = i.to_string().to_case(Case::Pascal);
+          if self.is_async {
+            format!(": Promise<{}>", parent)
+          } else {
+            format!(": {}", parent)
+          }
+        })
         .unwrap_or_else(|| "".to_owned()),
       _ => {
         let ret = if let Some(ret) = &self.ret {

crates/napi/src/bindgen_runtime/callback_info.rs

@@ -16,6 +16,7 @@ pub struct CallbackInfo<const N: usize> {
   env: sys::napi_env,
   pub this: sys::napi_value,
   pub args: [sys::napi_value; N],
+  this_reference: sys::napi_ref,
 }
 
 impl<const N: usize> CallbackInfo<N> {
@@ -24,6 +25,9 @@ impl<const N: usize> CallbackInfo<N> {
     env: sys::napi_env,
     callback_info: sys::napi_callback_info,
     required_argc: Option<usize>,
+    // for async class factory, the `this` will be used after the async call
+    // so we must create reference for it and use it after async resolved
+    use_after_async: bool,
   ) -> Result<Self> {
     let mut this = ptr::null_mut();
     let mut args = [ptr::null_mut(); N];
@@ -55,7 +59,21 @@ impl<const N: usize> CallbackInfo<N> {
       }
     }
 
-    Ok(Self { env, this, args })
+    let mut this_reference = ptr::null_mut();
+
+    if use_after_async {
+      check_status!(
+        unsafe { sys::napi_create_reference(env, this, 1, &mut this_reference) },
+        "Failed to create reference for `this` in async class factory"
+      )?;
+    }
+
+    Ok(Self {
+      env,
+      this,
+      args,
+      this_reference,
+    })
   }
 
   pub fn get_arg(&self, index: usize) -> sys::napi_value {
@@ -141,8 +159,18 @@ impl<const N: usize> CallbackInfo<N> {
     js_name: &str,
     obj: T,
   ) -> Result<(sys::napi_value, *mut T)> {
-    let this = self.this();
+    let mut this = self.this();
     let mut instance = ptr::null_mut();
+    if !self.this_reference.is_null() {
+      check_status!(
+        unsafe { sys::napi_get_reference_value(self.env, self.this_reference, &mut this) },
+        "Failed to get reference value for `this` in async class factory"
+      )?;
+      check_status!(
+        unsafe { sys::napi_delete_reference(self.env, self.this_reference) },
+        "Failed to delete reference for `this` in async class factory"
+      )?;
+    }
     ___CALL_FROM_FACTORY.with(|s| s.store(true, Ordering::Relaxed));
     let status =
       unsafe { sys::napi_new_instance(self.env, this, 0, ptr::null_mut(), &mut instance) };
@@ -154,6 +182,7 @@ impl<const N: usize> CallbackInfo<N> {
       unsafe { sys::napi_throw(self.env, exception) };
       return Ok((ptr::null_mut(), ptr::null_mut()));
     }
+    check_status!(status, "Failed to create instance of class `{}`", js_name)?;
     let obj = Box::new(obj);
     let initial_finalize: Box<dyn FnOnce()> = Box::new(|| {});
     let finalize_callbacks_ptr = Rc::into_raw(Rc::new(Cell::new(Box::into_raw(initial_finalize))));
@@ -164,7 +193,7 @@ impl<const N: usize> CallbackInfo<N> {
         sys::napi_wrap(
           self.env,
           instance,
-          value_ref as *mut c_void,
+          value_ref.cast(),
           Some(raw_finalize_unchecked::<T>),
           ptr::null_mut(),
           &mut object_ref,

crates/napi/src/env.rs

@@ -1084,7 +1084,7 @@ impl Env {
     T: 'static + Send,
     V: 'static + ToNapiValue,
     F: 'static + Send + Future<Output = Result<T>>,
-    R: 'static + Send + Sync + FnOnce(&mut Env, T) -> Result<V>,
+    R: 'static + Send + FnOnce(&mut Env, T) -> Result<V>,
   >(
     &self,
     fut: F,

crates/napi/src/tokio_runtime.rs

@@ -1,4 +1,4 @@
-use std::{future::Future, sync::RwLock};
+use std::{future::Future, marker::PhantomData, sync::RwLock};
 
 use once_cell::sync::Lazy;
 use tokio::runtime::Runtime;
@@ -83,11 +83,43 @@ pub fn within_runtime_if_available<F: FnOnce() -> T, T>(f: F) -> T {
   f()
 }
 
+struct SendableResolver<
+  Data: 'static + Send,
+  R: 'static + FnOnce(sys::napi_env, Data) -> Result<sys::napi_value>,
+> {
+  inner: R,
+  _data: PhantomData<Data>,
+}
+
+// the `SendableResolver` will be only called in the `threadsafe_function_call_js` callback
+// which means it will be always called in the Node.js JavaScript thread
+// so the inner function is not required to be `Send`
+// but the `Send` bound is required by the `execute_tokio_future` function
+unsafe impl<Data: 'static + Send, R: 'static + FnOnce(sys::napi_env, Data) -> Result<sys::napi_value>>
+  Send for SendableResolver<Data, R>
+{
+}
+
+impl<Data: 'static + Send, R: 'static + FnOnce(sys::napi_env, Data) -> Result<sys::napi_value>>
+  SendableResolver<Data, R>
+{
+  fn new(inner: R) -> Self {
+    Self {
+      inner,
+      _data: PhantomData,
+    }
+  }
+
+  fn resolve(self, env: sys::napi_env, data: Data) -> Result<sys::napi_value> {
+    (self.inner)(env, data)
+  }
+}
+
 #[allow(clippy::not_unsafe_ptr_arg_deref)]
 pub fn execute_tokio_future<
   Data: 'static + Send,
   Fut: 'static + Send + Future<Output = Result<Data>>,
-  Resolver: 'static + Send + Sync + FnOnce(sys::napi_env, Data) -> Result<sys::napi_value>,
+  Resolver: 'static + FnOnce(sys::napi_env, Data) -> Result<sys::napi_value>,
 >(
   env: sys::napi_env,
   fut: Fut,
@@ -95,10 +127,14 @@ pub fn execute_tokio_future<
 ) -> Result<sys::napi_value> {
   let (deferred, promise) = JsDeferred::new(env)?;
 
-  let inner = async move {
+  let sendable_resolver = SendableResolver::new(resolver);
+
+  let inner = async {
     match fut.await {
-      Ok(v) => deferred.resolve(|env| {
+      Ok(v) => deferred.resolve(move |env| {
-        resolver(env.raw(), v).map(|v| unsafe { JsUnknown::from_raw_unchecked(env.raw(), v) })
+        sendable_resolver
+          .resolve(env.raw(), v)
+          .map(|v| unsafe { JsUnknown::from_raw_unchecked(env.raw(), v) })
       }),
       Err(e) => deferred.reject(e),
     }

examples/napi/__tests__/__snapshots__/typegen.spec.ts.md

@@ -102,6 +102,8 @@ Generated by [AVA](https://avajs.dev).
     export class ClassWithFactory {␊
       name: string␊
       static withName(name: string): ClassWithFactory␊
+      static with4Name(name: string): Promise<ClassWithFactory>␊
+      static with4NameResult(name: string): Promise<ClassWithFactory>␊
       setName(name: string): this␊
     }␊
     ␊

examples/napi/__tests__/values.spec.ts

@@ -265,6 +265,13 @@ test('class factory', (t) => {
   )
 })
 
+test('async class factory', async (t) => {
+  const instance = await ClassWithFactory.with4Name('foo')
+  t.is(instance.name, 'foo-4')
+  const instance2 = await ClassWithFactory.with4NameResult('foo')
+  t.is(instance2.name, 'foo-4')
+})
+
 test('class constructor return Result', (t) => {
   const c = new Context()
   t.is(c.method(), 'not empty')

examples/napi/index.d.ts

@@ -92,6 +92,8 @@ export type Blake2bKey = Blake2BKey
 export class ClassWithFactory {
   name: string
   static withName(name: string): ClassWithFactory
+  static with4Name(name: string): Promise<ClassWithFactory>
+  static with4NameResult(name: string): Promise<ClassWithFactory>
   setName(name: string): this
 }
 

examples/napi/src/class_factory.rs

@@ -1,3 +1,9 @@
+use napi::Result;
+
+async fn always_4() -> i32 {
+  4
+}
+
 #[napi]
 pub struct ClassWithFactory {
   pub name: String,
@@ -10,6 +16,20 @@ impl ClassWithFactory {
     Self { name }
   }
 
+  #[napi(factory)]
+  pub async fn with_4_name(name: String) -> Self {
+    Self {
+      name: format!("{name}-{}", always_4().await),
+    }
+  }
+
+  #[napi(factory)]
+  pub async fn with_4_name_result(name: String) -> Result<Self> {
+    Ok(Self {
+      name: format!("{name}-{}", always_4().await),
+    })
+  }
+
   #[napi]
   pub fn set_name(&mut self, name: String) -> &Self {
     self.name = name;