feat(napi): implement external value

README.md

@@ -236,6 +236,7 @@ yarn test
 | Array                   | Array<any>             | 1                                                                               | v8.0.0               |
 | Vec<T>                  | Array<T>               | 1                                                                               | v8.0.0               |
 | Buffer                  | Buffer                 | 1                                                                               | v8.0.0               |
+| External<T>             | External<T>            | 1                                                                               | v8.0.0               |                          |
 | Null                    | null                   | 1                                                                               | v8.0.0               |
 | Undefined/()            | undefined              | 1                                                                               | v8.0.0               |
 | Result<()>              | Error                  | 1                                                                               | v8.0.0               |

cli/src/build.ts

@@ -344,7 +344,10 @@ async function processIntermediateTypeFile(
     .split('\n')
     .map((line) => line.trim())
     .filter(Boolean)
-  let dts = ''
+  let dts = `export class ExternalObject<T> {
+  private readonly __type: unique symbol;
+  [val: unique symbol]: T
+}\n`
   const classes = new Map<string, string>()
   const impls = new Map<string, string>()
 

crates/backend/src/typegen.rs

@@ -83,6 +83,7 @@ static KNOWN_TYPES: Lazy<HashMap<&'static str, &'static str>> = Lazy::new(|| {
     ("AbortSignal", "AbortSignal"),
     ("JsFunction", "(...args: any[]) => any"),
     ("JsGlobal", "typeof global"),
+    ("External", "ExternalObject<{}>"),
   ]);
 
   map

crates/napi/src/bindgen_runtime/js_values.rs

@@ -8,6 +8,7 @@ mod bigint;
 mod boolean;
 mod buffer;
 mod either;
+mod external;
 mod function;
 mod map;
 mod nil;
@@ -26,6 +27,7 @@ pub use array::*;
 pub use bigint::*;
 pub use buffer::*;
 pub use either::*;
+pub use external::*;
 #[cfg(feature = "napi4")]
 pub use function::*;
 pub use nil::*;

crates/napi/src/bindgen_runtime/js_values/external.rs

@@ -0,0 +1,110 @@
+use std::any::TypeId;
+
+use crate::{check_status, Error, Status, TaggedObject};
+
+use super::{FromNapiValue, ToNapiValue};
+
+pub struct External<T: 'static> {
+  obj: *mut TaggedObject<T>,
+  size_hint: usize,
+  pub adjusted_size: i64,
+}
+
+impl<T: 'static> External<T> {
+  pub fn new(value: T) -> Self {
+    Self {
+      obj: Box::into_raw(Box::new(TaggedObject::new(value))),
+      size_hint: 0,
+      adjusted_size: 0,
+    }
+  }
+
+  /// `size_hint` is a value to tell Node.js GC how much memory is used by this `External` object.
+  ///
+  /// If getting the exact `size_hint` is difficult, you can provide an approximate value, it's only effect to the GC.
+  ///
+  /// If your `External` object is not effect to GC, you can use `External::new` instead.
+  pub fn new_with_size_hint(value: T, size_hint: usize) -> Self {
+    Self {
+      obj: Box::into_raw(Box::new(TaggedObject::new(value))),
+      size_hint,
+      adjusted_size: 0,
+    }
+  }
+}
+
+impl<T: 'static> FromNapiValue for External<T> {
+  unsafe fn from_napi_value(
+    env: napi_sys::napi_env,
+    napi_val: napi_sys::napi_value,
+  ) -> crate::Result<Self> {
+    let mut unknown_tagged_object = std::ptr::null_mut();
+    check_status!(
+      napi_sys::napi_get_value_external(env, napi_val, &mut unknown_tagged_object),
+      "Failed to get external value"
+    )?;
+
+    let type_id = unknown_tagged_object as *const TypeId;
+    if *type_id == TypeId::of::<T>() {
+      let tagged_object = unknown_tagged_object as *mut TaggedObject<T>;
+      Ok(Self {
+        obj: tagged_object,
+        size_hint: 0,
+        adjusted_size: 0,
+      })
+    } else {
+      Err(Error::new(
+        Status::InvalidArg,
+        "T on `get_value_external` is not the type of wrapped object".to_owned(),
+      ))
+    }
+  }
+}
+
+impl<T: 'static> AsRef<T> for External<T> {
+  fn as_ref(&self) -> &T {
+    unsafe { Box::leak(Box::from_raw(self.obj)).object.as_ref().unwrap() }
+  }
+}
+
+impl<T: 'static> AsMut<T> for External<T> {
+  fn as_mut(&mut self) -> &mut T {
+    unsafe { Box::leak(Box::from_raw(self.obj)).object.as_mut().unwrap() }
+  }
+}
+
+impl<T: 'static> ToNapiValue for External<T> {
+  unsafe fn to_napi_value(
+    env: napi_sys::napi_env,
+    mut val: Self,
+  ) -> crate::Result<napi_sys::napi_value> {
+    let mut napi_value = std::ptr::null_mut();
+    check_status!(
+      napi_sys::napi_create_external(
+        env,
+        val.obj as *mut _,
+        Some(crate::raw_finalize::<T>),
+        Box::into_raw(Box::new(Some(val.size_hint as i64))) as *mut _,
+        &mut napi_value
+      ),
+      "Create external value failed"
+    )?;
+
+    let mut adjusted_external_memory_size = std::mem::MaybeUninit::new(0);
+
+    if val.size_hint != 0 {
+      check_status!(
+        napi_sys::napi_adjust_external_memory(
+          env,
+          val.size_hint as i64,
+          adjusted_external_memory_size.as_mut_ptr()
+        ),
+        "Adjust external memory failed"
+      )?;
+    };
+
+    val.adjusted_size = adjusted_external_memory_size.assume_init();
+
+    Ok(napi_value)
+  }
+}

crates/napi/src/env.rs

@@ -879,10 +879,12 @@ impl Env {
       )
     })?;
     if let Some(changed) = size_hint {
-      let mut adjusted_value = 0i64;
-      check_status!(unsafe {
-        sys::napi_adjust_external_memory(self.0, changed, &mut adjusted_value)
-      })?;
+      if changed != 0 {
+        let mut adjusted_value = 0i64;
+        check_status!(unsafe {
+          sys::napi_adjust_external_memory(self.0, changed, &mut adjusted_value)
+        })?;
+      }
     };
     Ok(unsafe { JsExternal::from_raw_unchecked(self.0, object_value) })
   }
@@ -1260,12 +1262,14 @@ pub(crate) unsafe extern "C" fn raw_finalize<T>(
   if !finalize_hint.is_null() {
     let size_hint = *Box::from_raw(finalize_hint as *mut Option<i64>);
     if let Some(changed) = size_hint {
-      let mut adjusted = 0i64;
-      let status = sys::napi_adjust_external_memory(env, -changed, &mut adjusted);
-      debug_assert!(
-        status == sys::Status::napi_ok,
-        "Calling napi_adjust_external_memory failed"
-      );
+      if changed != 0 {
+        let mut adjusted = 0i64;
+        let status = sys::napi_adjust_external_memory(env, -changed, &mut adjusted);
+        debug_assert!(
+          status == sys::Status::napi_ok,
+          "Calling napi_adjust_external_memory failed"
+        );
+      }
     };
   }
 }

examples/napi/__test__/typegen.spec.ts.md

@@ -8,7 +8,11 @@ Generated by [AVA](https://avajs.dev).
 
 > Snapshot 1
 
-    `export const DEFAULT_COST: number␊
+    `export class ExternalObject<T> {␊
+      private readonly __type: unique symbol;␊
+      [val: unique symbol]: T␊
+    }␊
+    export const DEFAULT_COST: number␊
     export function getWords(): Array<string>␊
     export function getNums(): Array<number>␊
     export function sumNums(nums: Array<number>): number␊
@@ -30,6 +34,10 @@ Generated by [AVA](https://avajs.dev).
     export enum CustomNumEnum { One = 1, Two = 2, Three = 3, Four = 4, Six = 6, Eight = 8, Nine = 9, Ten = 10 }␊
     export function enumToI32(e: CustomNumEnum): number␊
     export function throwError(): void␊
+    export function createExternal(size: number): ExternalObject<number>␊
+    export function createExternalString(content: string): ExternalObject<string>␊
+    export function getExternal(external: ExternalObject<number>): number␊
+    export function mutateExternal(external: ExternalObject<number>, newVal: number): void␊
     export function mapOption(val?: number | undefined | null): number | undefined | null␊
     export function add(a: number, b: number): number␊
     export function fibonacci(n: number): number␊

examples/napi/__test__/values.spec.ts

@@ -48,6 +48,10 @@ import {
   setSymbolInObj,
   createSymbol,
   threadsafeFunctionFatalMode,
+  createExternal,
+  getExternal,
+  mutateExternal,
+  createExternalString,
 } from '../'
 
 test('export const', (t) => {
@@ -237,13 +241,27 @@ test('either4', (t) => {
   t.is(either4({ v: 'world' }), 'world'.length)
 })
 
-test('async task without abort controller', async (t) => {
-  t.is(await withoutAbortController(1, 2), 3)
+test('external', (t) => {
+  const FX = 42
+  const ext = createExternal(FX)
+  t.is(getExternal(ext), FX)
+  mutateExternal(ext, FX + 1)
+  t.is(getExternal(ext), FX + 1)
+  // @ts-expect-error
+  t.throws(() => getExternal({}))
+  const ext2 = createExternalString('wtf')
+  // @ts-expect-error
+  const e = t.throws(() => getExternal(ext2))
+  t.is(e.message, 'T on `get_value_external` is not the type of wrapped object')
 })
 
 const AbortSignalTest =
   typeof AbortController !== 'undefined' ? test : test.skip
 
+AbortSignalTest('async task without abort controller', async (t) => {
+  t.is(await withoutAbortController(1, 2), 3)
+})
+
 AbortSignalTest('async task with abort controller', async (t) => {
   const ctrl = new AbortController()
   const promise = withAbortController(1, 2, ctrl.signal)

examples/napi/index.d.ts

@@ -1,3 +1,7 @@
+export class ExternalObject<T> {
+  private readonly __type: unique symbol;
+  [val: unique symbol]: T
+}
 export const DEFAULT_COST: number
 export function getWords(): Array<string>
 export function getNums(): Array<number>
@@ -20,6 +24,10 @@ export enum Kind { Dog = 0, Cat = 1, Duck = 2 }
 export enum CustomNumEnum { One = 1, Two = 2, Three = 3, Four = 4, Six = 6, Eight = 8, Nine = 9, Ten = 10 }
 export function enumToI32(e: CustomNumEnum): number
 export function throwError(): void
+export function createExternal(size: number): ExternalObject<number>
+export function createExternalString(content: string): ExternalObject<string>
+export function getExternal(external: ExternalObject<number>): number
+export function mutateExternal(external: ExternalObject<number>, newVal: number): void
 export function mapOption(val?: number | undefined | null): number | undefined | null
 export function add(a: number, b: number): number
 export function fibonacci(n: number): number

examples/napi/src/external.rs

@@ -0,0 +1,21 @@
+use napi::bindgen_prelude::*;
+
+#[napi]
+pub fn create_external(size: u32) -> External<u32> {
+  External::new(size)
+}
+
+#[napi]
+pub fn create_external_string(content: String) -> External<String> {
+  External::new(content)
+}
+
+#[napi]
+pub fn get_external(external: External<u32>) -> u32 {
+  *external.as_ref()
+}
+
+#[napi]
+pub fn mutate_external(mut external: External<u32>, new_val: u32) {
+  *external.as_mut() = new_val;
+}

examples/napi/src/lib.rs

@@ -15,6 +15,7 @@ mod class_factory;
 mod either;
 mod r#enum;
 mod error;
+mod external;
 mod nullable;
 mod number;
 mod object;