feat(neon): sys feature to give access to Node-API

.cargo/config.toml

@@ -4,4 +4,4 @@
 neon-check = " check  --all --all-targets --features napi-experimental,futures,external-buffers"
 neon-clippy = "clippy --all --all-targets --features napi-experimental,futures,external-buffers -- -A clippy::missing_safety_doc"
 neon-test = "  test   --all               --features=doc-dependencies,doc-comment,napi-experimental,futures,external-buffers"
-neon-doc = "   rustdoc -p neon            --features=doc-dependencies,napi-experimental,futures,external-buffers -- --cfg docsrs"
+neon-doc = "   rustdoc -p neon            --features=doc-dependencies,napi-experimental,futures,external-buffers,sys -- --cfg docsrs"

crates/neon/Cargo.toml

@@ -50,6 +50,10 @@ external-buffers = []
 # https://github.com/neon-bindings/rfcs/pull/46
 futures = ["tokio"]
 
+# Enable low-level system APIs. The `sys` API allows augmenting the Neon API
+# from external crates.
+sys = []
+
 # Default N-API version. Prefer to select a minimum required version.
 # DEPRECATED: This is an alias that should be removed
 napi-runtime = ["napi-8"]

crates/neon/src/context/internal.rs

@@ -2,10 +2,10 @@ use std::{cell::RefCell, ffi::c_void, mem::MaybeUninit};
 
 use crate::{
     context::ModuleContext,
-    handle::{Handle, Managed},
+    handle::Handle,
     result::NeonResult,
     sys::{self, raw},
-    types::JsObject,
+    types::{private::ValueInternal, JsObject},
 };
 
 #[repr(C)]
@@ -64,7 +64,7 @@ pub unsafe fn initialize_module(
     });
 
     let env = Env(env);
-    let exports = Handle::new_internal(JsObject::from_raw(env, exports.cast()));
+    let exports = Handle::new_internal(JsObject::from_local(env, exports.cast()));
 
     ModuleContext::with(env, exports, |cx| {
         let _ = init(cx);

crates/neon/src/context/mod.rs

@@ -147,7 +147,7 @@ pub use crate::types::buffer::lock::Lock;
 
 use crate::{
     event::TaskBuilder,
-    handle::{Handle, Managed},
+    handle::Handle,
     object::Object,
     result::{JsResult, NeonResult, Throw},
     sys::{
@@ -157,6 +157,7 @@ use crate::{
     types::{
         boxed::{Finalize, JsBox},
         error::JsError,
+        private::ValueInternal,
         Deferred, JsArray, JsArrayBuffer, JsBoolean, JsBuffer, JsFunction, JsNull, JsNumber,
         JsObject, JsPromise, JsString, JsUndefined, JsValue, StringResult, Value,
     },
@@ -276,9 +277,11 @@ pub trait Context<'a>: ContextInternal<'a> {
             phantom_inner: PhantomData,
         };
 
-        let escapee = unsafe { scope.escape(f(cx)?.to_raw()) };
+        let escapee = unsafe { scope.escape(f(cx)?.to_local()) };
 
-        Ok(Handle::new_internal(V::from_raw(self.env(), escapee)))
+        Ok(Handle::new_internal(unsafe {
+            V::from_local(self.env(), escapee)
+        }))
     }
 
     #[cfg_attr(
@@ -366,9 +369,9 @@ pub trait Context<'a>: ContextInternal<'a> {
     /// Throws a JS value.
     fn throw<T: Value, U>(&mut self, v: Handle<T>) -> NeonResult<U> {
         unsafe {
-            sys::error::throw(self.env().to_raw(), v.to_raw());
+            sys::error::throw(self.env().to_raw(), v.to_local());
+            Err(Throw::new())
         }
-        Err(Throw::new())
     }
 
     /// Creates a direct instance of the [`Error`](https://developer.mozilla.org/docs/Web/JavaScript/Reference/Global_Objects/Error) class.
@@ -505,6 +508,13 @@ pub trait Context<'a>: ContextInternal<'a> {
     {
         TaskBuilder::new(self, execute)
     }
+
+    #[cfg(feature = "sys")]
+    #[cfg_attr(docsrs, doc(cfg(feature = "sys")))]
+    /// Gets the raw `sys::Env` for usage with Node-API.
+    fn to_raw(&self) -> sys::Env {
+        self.env().to_raw()
+    }
 }
 
 /// An execution context of module initialization.
@@ -648,7 +658,7 @@ impl<'a> FunctionContext<'a> {
         };
 
         argv.get(i)
-            .map(|v| Handle::new_internal(JsValue::from_raw(self.env(), v)))
+            .map(|v| Handle::new_internal(unsafe { JsValue::from_local(self.env(), v) }))
     }
 
     /// Produces the `i`th argument and casts it to the type `V`, or throws an exception if `i` is greater than or equal to `self.len()` or cannot be cast to `V`.
@@ -726,3 +736,41 @@ impl<'a> ContextInternal<'a> for FinalizeContext<'a> {
 }
 
 impl<'a> Context<'a> for FinalizeContext<'a> {}
+
+#[cfg(feature = "sys")]
+#[cfg_attr(docsrs, doc(cfg(feature = "sys")))]
+/// An execution context constructed from a raw [`Env`](crate::sys::bindings::Env).
+pub struct SysContext<'cx> {
+    env: Env,
+    _phantom_inner: PhantomData<&'cx ()>,
+}
+
+#[cfg(feature = "sys")]
+impl<'cx> SysContext<'cx> {
+    /// Creates a context from a raw `Env`.
+    ///
+    /// # Safety
+    ///
+    /// Once a `SysContext` has been created, it is unsafe to use
+    /// the `Env`. The handle scope for the `Env` must be valid for
+    /// the lifetime `'cx`.
+    pub unsafe fn from_raw(env: sys::Env) -> Self {
+        Self {
+            env: env.into(),
+            _phantom_inner: PhantomData,
+        }
+    }
+}
+
+#[cfg(feature = "sys")]
+impl<'cx> SysContext<'cx> {}
+
+#[cfg(feature = "sys")]
+impl<'cx> ContextInternal<'cx> for SysContext<'cx> {
+    fn env(&self) -> Env {
+        self.env
+    }
+}
+
+#[cfg(feature = "sys")]
+impl<'cx> Context<'cx> for SysContext<'cx> {}

crates/neon/src/event/mod.rs

@@ -30,9 +30,10 @@
 //!
 //! ```
 //! # use neon::prelude::*;
-//! #
+//! # #[cfg(not(feature = "napi-6"))]
+//! # type Channel = ();
 //! # fn parse(filename: String, callback: Root<JsFunction>, channel: Channel) { }
-//! #
+//! # #[cfg(feature = "napi-6")]
 //! fn parse_async(mut cx: FunctionContext) -> JsResult<JsUndefined> {
 //!     // The types `String`, `Root<JsFunction>`, and `Channel` can all be
 //!     // sent across threads.
@@ -60,13 +61,16 @@
 //!
 //! ```
 //! # use neon::prelude::*;
+//! # #[cfg(not(feature = "napi-6"))]
+//! # type Channel = ();
 //! # use psd::Psd;
 //! # use anyhow::{Context as _, Result};
 //! #
 //! fn psd_from_filename(filename: String) -> Result<Psd> {
 //!     Psd::from_bytes(&std::fs::read(&filename)?).context("invalid psd file")
 //! }
 //!
+//! # #[cfg(feature = "napi-6")]
 //! fn parse(filename: String, callback: Root<JsFunction>, channel: Channel) {
 //!     let result = psd_from_filename(filename);
 //!

crates/neon/src/handle/mod.rs

@@ -61,31 +61,24 @@ use std::{
 pub use self::root::Root;
 
 use crate::{
-    context::{internal::Env, Context},
+    context::Context,
     handle::internal::{SuperType, TransparentNoCopyWrapper},
     result::{JsResult, ResultExt},
-    sys::{self, raw},
+    sys,
     types::Value,
 };
 
-/// The trait of data owned by the JavaScript engine and that can only be accessed via handles.
-pub trait Managed: TransparentNoCopyWrapper {
-    fn to_raw(&self) -> raw::Local;
-
-    fn from_raw(env: Env, h: raw::Local) -> Self;
-}
-
 /// A handle to a JavaScript value that is owned by the JavaScript engine.
 #[derive(Debug)]
 #[repr(transparent)]
-pub struct Handle<'a, T: Managed + 'a> {
+pub struct Handle<'a, V: Value + 'a> {
     // Contains the actual `Copy` JavaScript value data. It will be wrapped in
-    // in a `!Copy` type when dereferencing. Only `T` should be visible to the user.
-    value: <T as TransparentNoCopyWrapper>::Inner,
-    phantom: PhantomData<&'a T>,
+    // in a `!Copy` type when dereferencing. Only `V` should be visible to the user.
+    value: <V as TransparentNoCopyWrapper>::Inner,
+    phantom: PhantomData<&'a V>,
 }
 
-impl<'a, T: Managed> Clone for Handle<'a, T> {
+impl<'a, V: Value> Clone for Handle<'a, V> {
     fn clone(&self) -> Self {
         Self {
             value: self.value,
@@ -94,10 +87,10 @@ impl<'a, T: Managed> Clone for Handle<'a, T> {
     }
 }
 
-impl<'a, T: Managed> Copy for Handle<'a, T> {}
+impl<'a, V: Value> Copy for Handle<'a, V> {}
 
-impl<'a, T: Managed + 'a> Handle<'a, T> {
-    pub(crate) fn new_internal(value: T) -> Handle<'a, T> {
+impl<'a, V: Value + 'a> Handle<'a, V> {
+    pub(crate) fn new_internal(value: V) -> Handle<'a, V> {
         Handle {
             value: value.into_inner(),
             phantom: PhantomData,
@@ -196,19 +189,19 @@ impl<'a, T: Value> Handle<'a, T> {
         cx: &mut C,
         other: Handle<'b, U>,
     ) -> bool {
-        unsafe { sys::mem::strict_equals(cx.env().to_raw(), self.to_raw(), other.to_raw()) }
+        unsafe { sys::mem::strict_equals(cx.env().to_raw(), self.to_local(), other.to_local()) }
     }
 }
 
-impl<'a, T: Managed> Deref for Handle<'a, T> {
-    type Target = T;
-    fn deref(&self) -> &T {
+impl<'a, V: Value> Deref for Handle<'a, V> {
+    type Target = V;
+    fn deref(&self) -> &V {
         unsafe { mem::transmute(&self.value) }
     }
 }
 
-impl<'a, T: Managed> DerefMut for Handle<'a, T> {
-    fn deref_mut(&mut self) -> &mut T {
+impl<'a, V: Value> DerefMut for Handle<'a, V> {
+    fn deref_mut(&mut self) -> &mut V {
         unsafe { mem::transmute(&mut self.value) }
     }
 }

crates/neon/src/handle/root.rs

@@ -94,7 +94,7 @@ impl<T: Object> Root<T> {
     /// * N-API >= 6, Neon will drop from a global queue at a runtime cost
     pub fn new<'a, C: Context<'a>>(cx: &mut C, value: &T) -> Self {
         let env = cx.env().to_raw();
-        let internal = unsafe { reference::new(env, value.to_raw()) };
+        let internal = unsafe { reference::new(env, value.to_local()) };
 
         Self {
             internal: Some(NapiRef(internal as *mut _)),
@@ -159,7 +159,7 @@ impl<T: Object> Root<T> {
             internal.unref(env.to_raw());
         }
 
-        Handle::new_internal(T::from_raw(env, local))
+        Handle::new_internal(unsafe { T::from_local(env, local) })
     }
 
     /// Access the inner JavaScript object without consuming the `Root`
@@ -174,7 +174,7 @@ impl<T: Object> Root<T> {
         let env = cx.env();
         let local = unsafe { reference::get(env.to_raw(), self.as_napi_ref(cx).0 as *mut _) };
 
-        Handle::new_internal(T::from_raw(env, local))
+        Handle::new_internal(unsafe { T::from_local(env, local) })
     }
 
     fn as_napi_ref<'a, C: Context<'a>>(&self, cx: &mut C) -> &NapiRef {

crates/neon/src/lib.rs

@@ -86,6 +86,7 @@ pub mod object;
 pub mod prelude;
 pub mod reflect;
 pub mod result;
+#[cfg(not(feature = "sys"))]
 mod sys;
 #[cfg(feature = "napi-6")]
 pub mod thread;
@@ -95,6 +96,10 @@ pub mod thread;
 mod types_docs;
 mod types_impl;
 
+#[cfg(feature = "sys")]
+#[cfg_attr(docsrs, doc(cfg(feature = "sys")))]
+pub mod sys;
+
 pub use types_docs::exports as types;
 
 #[doc(hidden)]
@@ -127,3 +132,41 @@ static MODULE_TAG: once_cell::sync::Lazy<crate::sys::TypeTag> = once_cell::sync:
     // https://github.com/nodejs/node/blob/5fad0b93667ffc6e4def52996b9529ac99b26319/src/js_native_api_v8.cc#L2455
     crate::sys::TypeTag { lower, upper: 1 }
 });
+
+#[test]
+#[ignore]
+fn feature_matrix() {
+    use std::{env, process::Command};
+
+    const EXTERNAL_BUFFERS: &str = "external-buffers";
+    const FUTURES: &str = "futures";
+    const NODE_API_VERSIONS: &[&str] = &[
+        "napi-1", "napi-2", "napi-3", "napi-4", "napi-5", "napi-6", "napi-7", "napi-8",
+    ];
+
+    // If the number of features in Neon grows, we can use `itertools` to generate permutations.
+    // https://docs.rs/itertools/latest/itertools/trait.Itertools.html#method.permutations
+    const FEATURES: &[&[&str]] = &[
+        &[],
+        &[EXTERNAL_BUFFERS],
+        &[FUTURES],
+        &[EXTERNAL_BUFFERS, FUTURES],
+    ];
+
+    let cargo = env::var_os("CARGO").unwrap_or_else(|| "cargo".into());
+
+    for features in FEATURES {
+        for version in NODE_API_VERSIONS.iter().map(|f| f.to_string()) {
+            let features = features.iter().fold(version, |f, s| f + "," + s);
+            let status = Command::new(&cargo)
+                .args(["check", "-p", "neon", "--features"])
+                .arg(features)
+                .spawn()
+                .unwrap()
+                .wait()
+                .unwrap();
+
+            assert!(status.success());
+        }
+    }
+}