feat(neon): Implementation for JsPromise and TaskBuilder

RFC: neon-bindings/rfcs#35

.cargo/config.toml

@@ -1,9 +1,10 @@
 [alias]
 # Neon defines mutually exclusive feature flags which prevents using `cargo clippy --all-features`
 # The following aliases simplify linting the entire workspace
-check-napi = "check --all-targets --no-default-features -p neon -p neon-runtime -p neon-build -p neon-macros -p electron-tests -p napi-tests --features proc-macros,try-catch-api,napi-experimental"
+check-napi = "check --all-targets --no-default-features -p neon -p neon-runtime -p neon-build -p neon-macros -p electron-tests -p napi-tests --features proc-macros,try-catch-api,napi-experimental,promise-api,task-api"
 check-legacy = "check --all-targets --no-default-features -p neon -p neon-runtime -p neon-build -p neon-macros -p tests -p static_tests --features event-handler-api,proc-macros,try-catch-api,legacy-runtime"
 clippy-legacy = "clippy --all-targets --no-default-features -p neon -p neon-runtime -p neon-build -p neon-macros -p tests -p static_tests --features event-handler-api,proc-macros,try-catch-api,legacy-runtime -- -A clippy::missing_safety_doc"
-clippy-napi = "clippy --all-targets --no-default-features -p neon -p neon-runtime -p neon-build -p neon-macros -p electron-tests -p napi-tests --features proc-macros,try-catch-api,napi-experimental -- -A clippy::missing_safety_doc"
+clippy-napi = "clippy --all-targets --no-default-features -p neon -p neon-runtime -p neon-build -p neon-macros -p electron-tests -p napi-tests --features proc-macros,try-catch-api,napi-experimental,promise-api,task-api -- -A clippy::missing_safety_doc"
 neon-test = "test --no-default-features --features napi-experimental"
-neon-doc = "rustdoc --no-default-features --features=channel-api,napi-experimental,proc-macros,try-catch-api -- --cfg docsrs"
+neon-doc = "rustdoc --no-default-features --features=channel-api,napi-experimental,proc-macros,try-catch-api,promise-api,task-api -- --cfg docsrs"
+neon-doc-test = "test --doc --no-default-features --features=channel-api,napi-experimental,proc-macros,try-catch-api,promise-api,task-api"

Cargo.toml

@@ -78,6 +78,13 @@ event-queue-api = ["channel-api"]
 # Feature flag to include procedural macros
 proc-macros = ["neon-macros"]
 
+# Enable `JsPromise` and `Deferred`
+# https://github.com/neon-bindings/rfcs/pull/35
+promise-api = []
+# Enable `TaskBuilder`
+# https://github.com/neon-bindings/rfcs/pull/35
+task-api = []
+
 [package.metadata.docs.rs]
 no-default-features = true
 rustdoc-args = ["--cfg", "docsrs"]
@@ -86,6 +93,8 @@ features = [
     "napi-experimental",
     "proc-macros",
     "try-catch-api",
+    "promise-api",
+    "task-api",
 ]
 
 [workspace]

crates/neon-runtime/src/napi/async_work.rs

@@ -0,0 +1,138 @@
+//! Rust wrappers for Node-API simple asynchronous operations
+//!
+//! Unlike `napi_async_work` which threads a single mutable pointer to a data
+//! struct to both the `execute` and `complete` callbacks, the wrapper follows
+//! a more idiomatic Rust ownership pattern by passing the output of `execute`
+//! into the input of `complete`.
+//!
+//! https://nodejs.org/api/n-api.html#n_api_simple_asynchronous_operations
+
+use std::ffi::c_void;
+use std::mem;
+use std::ptr;
+
+use crate::napi::bindings as napi;
+use crate::raw::Env;
+
+type Execute<T, O> = fn(input: T) -> O;
+type Complete<O> = fn(env: Env, output: O);
+
+/// Schedule work to execute on the libuv thread pool
+///
+/// # Safety
+/// * `env` must be a valid `napi_env` for the current thread
+pub unsafe fn schedule<T, O>(env: Env, input: T, execute: Execute<T, O>, complete: Complete<O>)
+where
+    T: Send + 'static,
+    O: Send + 'static,
+{
+    let mut data = Box::new(Data {
+        state: State::Input(input),
+        execute,
+        complete,
+        // Work is initialized as a null pointer, but set by `create_async_work`
+        // `data` must not be used until this value has been set.
+        work: ptr::null_mut(),
+    });
+
+    // Store a pointer to `work` before ownership is transferred to `Box::into_raw`
+    let work = &mut data.work as *mut _;
+
+    // Create the `async_work`
+    assert_eq!(
+        napi::create_async_work(
+            env,
+            ptr::null_mut(),
+            super::string(env, "neon_async_work"),
+            Some(call_execute::<T, O>),
+            Some(call_complete::<T, O>),
+            Box::into_raw(data).cast(),
+            work,
+        ),
+        napi::Status::Ok,
+    );
+
+    // Queue the work
+    match napi::queue_async_work(env, *work) {
+        napi::Status::Ok => {}
+        status => {
+            // If queueing failed, delete the work to prevent a leak
+            napi::delete_async_work(env, *work);
+            assert_eq!(status, napi::Status::Ok);
+        }
+    }
+}
+
+/// A pointer to data is passed to the `execute` and `complete` callbacks
+struct Data<T, O> {
+    state: State<T, O>,
+    execute: Execute<T, O>,
+    complete: Complete<O>,
+    work: napi::AsyncWork,
+}
+
+/// State of the task that is transitioned by `execute` and `complete`
+enum State<T, O> {
+    /// Initial data input passed to `execute`
+    Input(T),
+    /// Transient state while `execute` is running
+    Executing,
+    /// Return data of `execute` passed to `complete`
+    Output(O),
+}
+
+impl<T, O> State<T, O> {
+    /// Return the input if `State::Input`, replacing with `State::Executing`
+    fn take_execute_input(&mut self) -> Option<T> {
+        match mem::replace(self, Self::Executing) {
+            Self::Input(input) => Some(input),
+            _ => None,
+        }
+    }
+
+    /// Return the output if `State::Output`, replacing with `State::Executing`
+    fn into_output(self) -> Option<O> {
+        match self {
+            Self::Output(output) => Some(output),
+            _ => None,
+        }
+    }
+}
+
+/// Callback executed on the libuv thread pool
+///
+/// # Safety
+/// * `Env` should not be used because it could attempt to call JavaScript
+/// * `data` is expected to be a pointer to `Data<T, O>`
+unsafe extern "C" fn call_execute<T, O>(_: Env, data: *mut c_void) {
+    let data = &mut *data.cast::<Data<T, O>>();
+    // `unwrap` is ok because `call_execute` should be called exactly once
+    // after initialization
+    let input = data.state.take_execute_input().unwrap();
+    let output = (data.execute)(input);
+
+    data.state = State::Output(output);
+}
+
+/// Callback executed on the JavaScript main thread
+///
+/// # Safety
+/// * `data` is expected to be a pointer to `Data<T, O>`
+unsafe extern "C" fn call_complete<T, O>(env: Env, status: napi::Status, data: *mut c_void) {
+    let Data {
+        state,
+        complete,
+        work,
+        ..
+    } = *Box::<Data<T, O>>::from_raw(data.cast());
+
+    napi::delete_async_work(env, work);
+
+    match status {
+        // `unwrap` is okay because `call_complete` should be called exactly once
+        // if and only if `call_execute` has completed successfully
+        napi::Status::Ok => complete(env, state.into_output().unwrap()),
+        napi::Status::Cancelled => {}
+        _ => assert_eq!(status, napi::Status::Ok),
+    }
+}

crates/neon-runtime/src/napi/bindings/functions.rs

@@ -57,6 +57,7 @@ mod napi1 {
             fn is_buffer(env: Env, value: Value, result: *mut bool) -> Status;
             fn is_error(env: Env, value: Value, result: *mut bool) -> Status;
             fn is_array(env: Env, value: Value, result: *mut bool) -> Status;
+            fn is_promise(env: Env, value: Value, result: *mut bool) -> Status;
 
             fn get_value_string_utf8(
                 env: Env,
@@ -209,6 +210,22 @@ mod napi1 {
             ) -> Status;
 
             fn run_script(env: Env, script: Value, result: *mut Value) -> Status;
+
+            fn create_async_work(
+                env: Env,
+                async_resource: Value,
+                async_resource_name: Value,
+                execute: AsyncExecuteCallback,
+                complete: AsyncCompleteCallback,
+                data: *mut c_void,
+                result: *mut AsyncWork,
+            ) -> Status;
+
+            fn delete_async_work(env: Env, work: AsyncWork) -> Status;
+            fn queue_async_work(env: Env, work: AsyncWork) -> Status;
+            fn create_promise(env: Env, deferred: *mut Deferred, promise: *mut Value) -> Status;
+            fn resolve_deferred(env: Env, deferred: Deferred, resolution: Value) -> Status;
+            fn reject_deferred(env: Env, deferred: Deferred, rejection: Value) -> Status;
         }
     );
 }

crates/neon-runtime/src/napi/bindings/mod.rs

@@ -169,8 +169,8 @@ macro_rules! generate {
 use std::sync::Once;
 
 pub(crate) use functions::*;
-pub use types::TypedArrayType;
 pub(crate) use types::*;
+pub use types::{Deferred, TypedArrayType};
 
 mod functions;
 mod types;

crates/neon-runtime/src/napi/bindings/types.rs

@@ -29,6 +29,7 @@ pub type CallbackInfo = *mut CallbackInfo__;
 pub struct EscapableHandleScope__ {
     _unused: [u8; 0],
 }
+
 pub type EscapableHandleScope = *mut EscapableHandleScope__;
 
 #[repr(C)]
@@ -203,3 +204,24 @@ impl std::ops::BitAndAssign for KeyFilter {
         self.0 &= rhs.0;
     }
 }
+
+#[repr(C)]
+#[derive(Debug, Copy, Clone)]
+pub struct AsyncWork__ {
+    _unused: [u8; 0],
+}
+
+pub type AsyncWork = *mut AsyncWork__;
+
+pub type AsyncExecuteCallback = Option<unsafe extern "C" fn(env: Env, data: *mut c_void)>;
+
+pub type AsyncCompleteCallback =
+    Option<unsafe extern "C" fn(env: Env, status: Status, data: *mut c_void)>;
+
+#[repr(C)]
+#[derive(Debug, Copy, Clone)]
+pub struct Deferred__ {
+    _unused: [u8; 0],
+}
+
+pub type Deferred = *mut Deferred__;

crates/neon-runtime/src/napi/mod.rs

@@ -1,5 +1,6 @@
 pub mod array;
 pub mod arraybuffer;
+pub mod async_work;
 pub mod buffer;
 pub mod call;
 pub mod convert;
@@ -13,6 +14,7 @@ pub mod lifecycle;
 pub mod mem;
 pub mod object;
 pub mod primitive;
+pub mod promise;
 pub mod raw;
 pub mod reference;
 pub mod scope;
@@ -23,4 +25,29 @@ pub mod tsfn;
 pub mod typedarray;
 
 mod bindings;
+
 pub use bindings::*;
+
+use std::mem::MaybeUninit;
+
+/// Create a JavaScript `String`, panicking if unsuccessful
+///
+/// # Safety
+/// * `env` is a `napi_env` valid for the current thread
+/// * The returned value does not outlive `env`
+unsafe fn string(env: Env, s: impl AsRef<str>) -> raw::Local {
+    let s = s.as_ref();
+    let mut result = MaybeUninit::uninit();
+
+    assert_eq!(
+        create_string_utf8(
+            env,
+            s.as_bytes().as_ptr() as *const _,
+            s.len(),
+            result.as_mut_ptr(),
+        ),
+        Status::Ok,
+    );
+
+    result.assume_init()
+}

crates/neon-runtime/src/napi/promise.rs

@@ -0,0 +1,66 @@
+//! JavaScript Promise and Deferred handle
+//!
+//! https://nodejs.org/api/n-api.html#n_api_promises
+
+use std::mem::MaybeUninit;
+use std::ptr;
+
+use crate::napi::bindings as napi;
+use crate::raw::Env;
+
+/// Create a `Promise` and a `napi::Deferred` handle for resolving it
+///
+/// # Safety
+/// * `env` is a valid `napi_env` for the current thread
+/// * The returned `napi::Value` does not outlive `env`
+pub unsafe fn create(env: Env) -> (napi::Deferred, napi::Value) {
+    let mut deferred = MaybeUninit::uninit();
+    let mut promise = MaybeUninit::uninit();
+
+    assert_eq!(
+        napi::create_promise(env, deferred.as_mut_ptr(), promise.as_mut_ptr()),
+        napi::Status::Ok,
+    );
+
+    (deferred.assume_init(), promise.assume_init())
+}
+
+/// Resolve a promise from a `napi::Deferred` handle
+///
+/// # Safety
+/// * `env` is a valid `napi_env` for the current thread
+/// * `resolution` is a valid `napi::Value`
+pub unsafe fn resolve(env: Env, deferred: napi::Deferred, resolution: napi::Value) {
+    assert_eq!(
+        napi::resolve_deferred(env, deferred, resolution),
+        napi::Status::Ok,
+    );
+}
+
+/// Rejects a promise from a `napi::Deferred` handle
+///
+/// # Safety
+/// * `env` is a valid `napi_env` for the current thread
+/// * `rejection` is a valid `napi::Value`
+pub unsafe fn reject(env: Env, deferred: napi::Deferred, rejection: napi::Value) {
+    assert_eq!(
+        napi::reject_deferred(env, deferred, rejection),
+        napi::Status::Ok,
+    );
+}
+
+/// Rejects a promise from a `napi::Deferred` handle with a string message
+///
+/// # Safety
+/// * `env` is a valid `napi_env` for the current thread
+pub unsafe fn reject_err_message(env: Env, deferred: napi::Deferred, msg: impl AsRef<str>) {
+    let msg = super::string(env, msg);
+    let mut err = MaybeUninit::uninit();
+
+    assert_eq!(
+        napi::create_error(env, ptr::null_mut(), msg, err.as_mut_ptr()),
+        napi::Status::Ok,
+    );
+
+    reject(env, deferred, err.assume_init());
+}

crates/neon-runtime/src/napi/tag.rs

@@ -99,3 +99,16 @@ pub unsafe fn is_date(env: Env, val: Local) -> bool {
     );
     result
 }
+
+/// Is `val` a Promise?
+///
+/// # Safety
+/// * `env` is a valid `napi_env` for the current thread
+pub unsafe fn is_promise(env: Env, val: Local) -> bool {
+    let mut result = false;
+    assert_eq!(
+        napi::is_promise(env, val, &mut result as *mut _),
+        napi::Status::Ok
+    );
+    result
+}