Type extractors for common container types (#1091)

Implement type extractors for common container types in the standard library, so that they don't required explicit Boxed wrapping with JsBox in userland.

Container type implementations included in this commit:

- RefCell
  - impl TryIntoJs for RefCell
  - impl TryFromJs for &RefCell
  - impl TryFromJs for Ref
  - impl TryFromJs for RefMut
- Rc
  - impl TryIntoJs for Rc
  - impl TryFromJs for Rc
- Arc
  - impl TryIntoJs for Arc
  - impl TryFromJs for Arc

Author: dherman

crates/neon/src/types_impl/boxed.rs

@@ -234,14 +234,10 @@ impl<T: 'static> ValueInternal for JsBox<T> {
 /// until the application terminates, only that its lifetime is indefinite.
 impl<T: Finalize + 'static> JsBox<T> {
     /// Constructs a new `JsBox` containing `value`.
-    pub fn new<'a, C>(cx: &mut C, value: T) -> Handle<'a, JsBox<T>>
-    where
-        C: Context<'a>,
-        T: 'static,
-    {
+    pub fn new<'cx, C: Context<'cx>>(cx: &mut C, value: T) -> Handle<'cx, JsBox<T>> {
         // This function will execute immediately before the `JsBox` is garbage collected.
         // It unwraps the `napi_external`, downcasts the `BoxAny` and moves the type
-        // out of the `Box`. Lastly, it calls the trait method `Finalize::fianlize` of the
+        // out of the `Box`. Lastly, it calls the trait method `Finalize::finalize` of the
         // contained value `T`.
         fn finalizer<U: Finalize + 'static>(env: raw::Env, data: BoxAny) {
             let data = *data.downcast::<U>().unwrap();
@@ -250,12 +246,29 @@ impl<T: Finalize + 'static> JsBox<T> {
             Cx::with_context(env, move |mut cx| data.finalize(&mut cx));
         }
 
+        Self::create_external(cx, value, finalizer::<T>)
+    }
+}
+
+impl<T: 'static> JsBox<T> {
+    pub(crate) fn manually_finalize<'cx>(cx: &mut Cx<'cx>, value: T) -> Handle<'cx, JsBox<T>> {
+        fn finalizer(_env: raw::Env, _data: BoxAny) {}
+
+        Self::create_external(cx, value, finalizer)
+    }
+
+    fn create_external<'cx, C: Context<'cx>>(
+        cx: &mut C,
+        value: T,
+        finalizer: fn(raw::Env, BoxAny),
+    ) -> Handle<'cx, JsBox<T>> {
         let v = Box::new(value) as BoxAny;
+
         // Since this value was just constructed, we know it is `T`
         let raw_data = &*v as *const dyn Any as *const T;
-        let local = unsafe { external::create(cx.env().to_raw(), v, finalizer::<T>) };
+        let local = unsafe { external::create(cx.env().to_raw(), v, finalizer) };
 
-        Handle::new_internal(Self(JsBoxInner { local, raw_data }))
+        Handle::new_internal(JsBox(JsBoxInner { local, raw_data }))
     }
 }
 

crates/neon/src/types_impl/extract/container.rs

@@ -0,0 +1,126 @@
+use std::{
+    cell::{Ref, RefCell, RefMut},
+    rc::Rc,
+    sync::Arc,
+};
+
+use crate::{
+    context::{Context, Cx},
+    handle::Handle,
+    result::{JsResult, NeonResult},
+    types::{
+        extract::{TryFromJs, TryIntoJs},
+        JsBox, JsValue,
+    },
+};
+
+use super::error::TypeExpected;
+
+impl<'cx, T: 'static> TryFromJs<'cx> for &'cx RefCell<T> {
+    type Error = TypeExpected<JsBox<RefCell<T>>>;
+
+    fn try_from_js(
+        cx: &mut Cx<'cx>,
+        v: Handle<'cx, JsValue>,
+    ) -> NeonResult<Result<Self, Self::Error>> {
+        match v.downcast::<JsBox<RefCell<T>>, _>(cx) {
+            Ok(v) => Ok(Ok(JsBox::deref(&v))),
+            Err(_) => Ok(Err(TypeExpected::new())),
+        }
+    }
+}
+
+impl<'cx, T: 'static> TryFromJs<'cx> for Ref<'cx, T> {
+    type Error = TypeExpected<JsBox<RefCell<T>>>;
+
+    fn try_from_js(
+        cx: &mut Cx<'cx>,
+        v: Handle<'cx, JsValue>,
+    ) -> NeonResult<Result<Self, Self::Error>> {
+        match v.downcast::<JsBox<RefCell<T>>, _>(cx) {
+            Ok(v) => match JsBox::deref(&v).try_borrow() {
+                Ok(r) => Ok(Ok(r)),
+                Err(_) => cx.throw_error("RefCell is already mutably borrowed"),
+            },
+            Err(_) => Ok(Err(TypeExpected::new())),
+        }
+    }
+}
+
+impl<'cx, T: 'static> TryFromJs<'cx> for RefMut<'cx, T> {
+    type Error = TypeExpected<JsBox<RefCell<T>>>;
+
+    fn try_from_js(
+        cx: &mut Cx<'cx>,
+        v: Handle<'cx, JsValue>,
+    ) -> NeonResult<Result<Self, Self::Error>> {
+        match v.downcast::<JsBox<RefCell<T>>, _>(cx) {
+            Ok(v) => match JsBox::deref(&v).try_borrow_mut() {
+                Ok(r) => Ok(Ok(r)),
+                Err(_) => cx.throw_error("RefCell is already borrowed"),
+            },
+            Err(_) => Ok(Err(TypeExpected::new())),
+        }
+    }
+}
+
+impl<'cx, T> TryIntoJs<'cx> for RefCell<T>
+where
+    T: 'static,
+{
+    type Value = JsBox<RefCell<T>>;
+
+    fn try_into_js(self, cx: &mut Cx<'cx>) -> JsResult<'cx, Self::Value> {
+        Ok(JsBox::manually_finalize(cx, self))
+    }
+}
+
+impl<'cx, T: 'static> TryFromJs<'cx> for Rc<T> {
+    type Error = TypeExpected<JsBox<Rc<T>>>;
+
+    fn try_from_js(
+        cx: &mut Cx<'cx>,
+        v: Handle<'cx, JsValue>,
+    ) -> NeonResult<Result<Self, Self::Error>> {
+        match v.downcast::<JsBox<Rc<T>>, _>(cx) {
+            Ok(v) => Ok(Ok(Rc::clone(&v))),
+            Err(_) => Ok(Err(TypeExpected::new())),
+        }
+    }
+}
+
+impl<'cx, T> TryIntoJs<'cx> for Rc<T>
+where
+    T: 'static,
+{
+    type Value = JsBox<Rc<T>>;
+
+    fn try_into_js(self, cx: &mut Cx<'cx>) -> JsResult<'cx, Self::Value> {
+        Ok(JsBox::manually_finalize(cx, self))
+    }
+}
+
+impl<'cx, T: 'static> TryFromJs<'cx> for Arc<T> {
+    type Error = TypeExpected<JsBox<Arc<T>>>;
+
+    fn try_from_js(
+        cx: &mut Cx<'cx>,
+        v: Handle<'cx, JsValue>,
+    ) -> NeonResult<Result<Self, Self::Error>> {
+        match v.downcast::<JsBox<Arc<T>>, _>(cx) {
+            Ok(v) => Ok(Ok(Arc::clone(&v))),
+            Err(_) => Ok(Err(TypeExpected::new())),
+        }
+    }
+}
+
+impl<'cx, T> TryIntoJs<'cx> for Arc<T>
+where
+    T: 'static,
+{
+    type Value = JsBox<Arc<T>>;
+
+    fn try_into_js(self, cx: &mut Cx<'cx>) -> JsResult<'cx, Self::Value> {
+        Ok(JsBox::manually_finalize(cx, self))
+    }
+}

crates/neon/src/types_impl/extract/mod.rs

@@ -126,6 +126,7 @@ pub mod json;
 
 mod boxed;
 mod buffer;
+mod container;
 mod either;
 mod error;
 mod private;

crates/neon/src/types_impl/extract/private.rs

@@ -1,3 +1,9 @@
+use std::{
+    cell::{Ref, RefCell, RefMut},
+    rc::Rc,
+    sync::Arc,
+};
+
 use crate::{
     context::FunctionContext,
     handle::{Handle, Root},
@@ -45,4 +51,16 @@ impl<T, E> Sealed for Result<T, E> {}
 
 impl<'cx, T> Sealed for Box<T> where T: TryIntoJs<'cx> {}
 
+impl<T> Sealed for RefCell<T> {}
+
+impl<T> Sealed for &RefCell<T> {}
+
+impl<T> Sealed for Arc<T> {}
+
+impl<T> Sealed for Rc<T> {}
+
+impl<T> Sealed for Ref<'_, T> {}
+
+impl<T> Sealed for RefMut<'_, T> {}
+
 impl_sealed!(u8, u16, u32, i8, i16, i32, f32, f64, bool, String, Date, Throw, Error,);

package-lock.json

@@ -0,0 +1,74 @@
+const addon = require("..");
+const { expect } = require("chai");
+const assert = require("chai").assert;
+
+describe("Container type extractors", function () {
+  it("can produce and consume a RefCell", function () {
+    const cell = addon.createStringRefCell("my sekret mesij");
+    const s = addon.readStringRefCell(cell);
+    assert.strictEqual(s, "my sekret mesij");
+  });
+
+  it("can produce and modify a RefCell", function () {
+    const cell = addon.createStringRefCell("new");
+    addon.writeStringRefCell(cell, "modified");
+    assert.strictEqual(addon.readStringRefCell(cell), "modified");
+  });
+
+  it("can concatenate a RefCell<String> with a String", function () {
+    const cell = addon.createStringRefCell("hello");
+    const s = addon.stringRefCellConcat(cell, " world");
+    assert.strictEqual(s, "hello world");
+  });
+
+  it("fail with a type error when not given a RefCell", function () {
+    try {
+      addon.stringRefCellConcat("hello", " world");
+      assert.fail("should have thrown");
+    } catch (err) {
+      assert.instanceOf(err, TypeError);
+      assert.strictEqual(
+        err.message,
+        "expected neon::types_impl::boxed::JsBox<core::cell::RefCell<alloc::string::String>>"
+      );
+    }
+  });
+
+  it("dynamically fail when borrowing a mutably borrowed RefCell", function () {
+    const cell = addon.createStringRefCell("hello");
+    try {
+      addon.borrowMutAndThen(cell, () => {
+        addon.stringRefConcat(cell, " world");
+      });
+      assert.fail("should have thrown");
+    } catch (err) {
+      assert.instanceOf(err, Error);
+      assert.include(err.message, "already mutably borrowed");
+    }
+  });
+
+  it("dynamically fail when modifying a borrowed RefCell", function () {
+    const cell = addon.createStringRefCell("hello");
+    try {
+      addon.borrowAndThen(cell, () => {
+        addon.writeStringRef(cell, "world");
+      });
+      assert.fail("should have thrown");
+    } catch (err) {
+      assert.instanceOf(err, Error);
+      assert.include(err.message, "already borrowed");
+    }
+  });
+
+  it("can produce and consume an Rc", function () {
+    const cell = addon.createStringRc("my sekret mesij");
+    const s = addon.readStringRc(cell);
+    assert.strictEqual(s, "my sekret mesij");
+  });
+
+  it("can produce and consume an Arc", function () {
+    const cell = addon.createStringArc("my sekret mesij");
+    const s = addon.readStringArc(cell);
+    assert.strictEqual(s, "my sekret mesij");
+  });
+});

test/napi/lib/container.js

@@ -0,0 +1,80 @@
+use neon::prelude::*;
+
+use std::{
+    cell::{Ref, RefCell, RefMut},
+    rc::Rc,
+    sync::Arc,
+};
+
+#[neon::export]
+fn create_string_ref_cell(s: String) -> RefCell<String> {
+    RefCell::new(s)
+}
+
+#[neon::export]
+fn read_string_ref_cell(s: &RefCell<String>) -> String {
+    s.borrow().clone()
+}
+
+#[neon::export]
+fn write_string_ref_cell(s: &RefCell<String>, value: String) {
+    *s.borrow_mut() = value;
+}
+
+#[neon::export]
+fn string_ref_cell_concat(lhs: &RefCell<String>, rhs: String) -> String {
+    lhs.borrow().clone() + &rhs
+}
+
+#[neon::export]
+fn string_ref_concat(lhs: Ref<String>, rhs: String) -> String {
+    lhs.clone() + &rhs
+}
+
+#[neon::export]
+fn write_string_ref(mut s: RefMut<String>, value: String) {
+    *s = value;
+}
+
+#[neon::export]
+fn borrow_and_then<'cx>(
+    cx: &mut Cx<'cx>,
+    cell: &RefCell<String>,
+    f: Handle<JsFunction>,
+) -> JsResult<'cx, JsString> {
+    let s = cell.borrow();
+    f.bind(cx).exec()?;
+    Ok(cx.string(s.clone()))
+}
+
+#[neon::export]
+fn borrow_mut_and_then<'cx>(
+    cx: &mut Cx<'cx>,
+    cell: &RefCell<String>,
+    f: Handle<JsFunction>,
+) -> JsResult<'cx, JsString> {
+    let mut s = cell.borrow_mut();
+    f.bind(cx).exec()?;
+    *s = "overwritten".to_string();
+    Ok(cx.string(s.clone()))
+}
+
+#[neon::export]
+fn create_string_rc(s: String) -> Rc<String> {
+    Rc::new(s)
+}
+
+#[neon::export]
+fn read_string_rc(s: Rc<String>) -> String {
+    (*s).clone()
+}
+
+#[neon::export]
+fn create_string_arc(s: String) -> Arc<String> {
+    Arc::new(s)
+}
+
+#[neon::export]
+fn read_string_arc(s: Arc<String>) -> String {
+    (*s).clone()
+}

test/napi/src/js/container.rs

@@ -12,6 +12,7 @@ mod js {
     pub mod bigint;
     pub mod boxed;
     pub mod coercions;
+    pub mod container;
     pub mod date;
     pub mod errors;
     pub mod export;