fix(napi): segfault when ThreadsafeFunction's callback closure captures data (#1281)

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

@@ -193,6 +193,7 @@ Generated by [AVA](https://avajs.dev).
     export function threadsafeFunctionThrowError(cb: (...args: any[]) => any): void␊
     export function threadsafeFunctionFatalMode(cb: (...args: any[]) => any): void␊
     export function threadsafeFunctionFatalModeError(cb: (...args: any[]) => any): void␊
+    export function threadsafeFunctionClosureCapture(func: (...args: any[]) => any): void␊
     export function useTokioWithoutAsync(): void␊
     export function getBuffer(): Buffer␊
     export function appendBuffer(buf: Buffer): Buffer␊

examples/napi/__test__/values.spec.ts

@@ -50,6 +50,7 @@ import {
   bigintGetU64AsString,
   callThreadsafeFunction,
   threadsafeFunctionThrowError,
+  threadsafeFunctionClosureCapture,
   asyncPlus100,
   getGlobal,
   getUndefined,
@@ -691,6 +692,15 @@ Napi4Test('throw error from thread safe function', async (t) => {
   t.is(err!.message, 'ThrowFromNative')
 })
 
+Napi4Test('thread safe function closure capture data', (t) => {
+  return new Promise((resolve) => {
+    threadsafeFunctionClosureCapture(() => {
+      resolve()
+      t.pass()
+    })
+  })
+})
+
 Napi4Test('resolve value from thread safe function fatal mode', async (t) => {
   const tsfnFatalMode = new Promise<boolean>((resolve) => {
     threadsafeFunctionFatalMode(resolve)

examples/napi/index.d.ts

@@ -183,6 +183,7 @@ export function callThreadsafeFunction(callback: (...args: any[]) => any): void
 export function threadsafeFunctionThrowError(cb: (...args: any[]) => any): void
 export function threadsafeFunctionFatalMode(cb: (...args: any[]) => any): void
 export function threadsafeFunctionFatalModeError(cb: (...args: any[]) => any): void
+export function threadsafeFunctionClosureCapture(func: (...args: any[]) => any): void
 export function useTokioWithoutAsync(): void
 export function getBuffer(): Buffer
 export function appendBuffer(buf: Buffer): Buffer

examples/napi/src/threadsafe_function.rs

@@ -3,7 +3,7 @@ use std::thread;
 use napi::{
   bindgen_prelude::*,
   threadsafe_function::{ErrorStrategy, ThreadsafeFunction, ThreadsafeFunctionCallMode},
-  JsBoolean,
+  JsBoolean, JsString,
 };
 
 #[napi]
@@ -61,3 +61,18 @@ pub fn threadsafe_function_fatal_mode_error(cb: JsFunction) -> Result<()> {
   });
   Ok(())
 }
+
+#[napi]
+fn threadsafe_function_closure_capture(func: JsFunction) -> napi::Result<()> {
+  let str = "test";
+  let tsfn: ThreadsafeFunction<()> = func
+    .create_threadsafe_function(0, move |_| {
+      println!("{}", str); // str is NULL at this point
+      Ok(Vec::<JsString>::new())
+    })
+    .unwrap();
+
+  tsfn.call(Ok(()), ThreadsafeFunctionCallMode::NonBlocking);
+
+  Ok(())
+}