Implement `napi_ref_threadsafe_function` (#4156)

* Implement napi_ref_threadsafe_function

* work on this

* i hate event loops

* little better

* clean

3 files changed, 24 insertions, 4 deletions

diff --git a/src/bun.js/base.zig b/src/bun.js/base.zig
index b08b82c40..e72e196a3 100644
--- a/src/bun.js/base.zig
+++ b/src/bun.js/base.zig
@@ -1682,6 +1682,14 @@ pub const PollRef = struct {
         this.status = .active;
         vm.uws_event_loop.?.refConcurrently();
     }
+
+    pub fn refConcurrentlyFromEventLoop(this: *PollRef, loop: *JSC.EventLoop) void {
+        this.refConcurrently(loop.virtual_machine);
+    }
+
+    pub fn unrefConcurrentlyFromEventLoop(this: *PollRef, loop: *JSC.EventLoop) void {
+        this.unrefConcurrently(loop.virtual_machine);
+    }
 };
 
 const KQueueGenerationNumber = if (Environment.isMac and Environment.allow_assert) usize else u0;
diff --git a/src/bun.js/bindings/napi.cpp b/src/bun.js/bindings/napi.cpp
index 8a77723e2..2562242a8 100644
--- a/src/bun.js/bindings/napi.cpp
+++ b/src/bun.js/bindings/napi.cpp
@@ -46,6 +46,8 @@
 #include "JavaScriptCore/JSSourceCode.h"
 #include "JavaScriptCore/JSNativeStdFunction.h"
 #include "JavaScriptCore/BigIntObject.h"
+#include "ScriptExecutionContext.h"
+#include "Strong.h"
 
 #include "../modules/ObjectModule.h"
 
@@ -1763,7 +1765,16 @@ extern "C" napi_status napi_create_external(napi_env env, void* data,
 
     auto* structure = Bun::NapiExternal::createStructure(vm, globalObject, globalObject->objectPrototype());
     JSValue value = JSValue(Bun::NapiExternal::create(vm, structure, data, finalize_hint, finalize_cb));
-    JSC::EnsureStillAliveScope ensureStillAlive(value);
+
+    // With `fsevents`, their napi_create_external seems to get immediatly garbage
+    // collected for some unknown reason.
+    // See https://github.com/oven-sh/bun/issues/3978 and `fsevents.test.ts`
+    JSC::Strong<Unknown>* strong = new JSC::Strong<Unknown>(vm, value);
+    globalObject->scriptExecutionContext()->postTask([strong](auto& context) -> void {
+        strong->clear();
+        delete strong;
+    });
+
     *result = toNapi(value);
     return napi_ok;
 }
diff --git a/src/napi/napi.zig b/src/napi/napi.zig
index 99a49bb96..1d3e3e811 100644
--- a/src/napi/napi.zig
+++ b/src/napi/napi.zig
@@ -1210,7 +1210,7 @@ pub const ThreadSafeFunction = struct {
     /// Neither does napi_unref_threadsafe_function mark the thread-safe
     /// functions as able to be destroyed nor does napi_ref_threadsafe_function
     /// prevent it from being destroyed.
-    ref_for_process_exit: bool = false,
+    poll_ref: JSC.PollRef,
 
     owning_threads: std.AutoArrayHashMapUnmanaged(u64, void) = .{},
     owning_thread_lock: Lock = Lock.init(),
@@ -1345,11 +1345,11 @@ pub const ThreadSafeFunction = struct {
     }
 
     pub fn ref(this: *ThreadSafeFunction) void {
-        this.ref_for_process_exit = true;
+        this.poll_ref.refConcurrentlyFromEventLoop(this.event_loop);
     }
 
     pub fn unref(this: *ThreadSafeFunction) void {
-        this.ref_for_process_exit = false;
+        this.poll_ref.unrefConcurrentlyFromEventLoop(this.event_loop);
     }
 
     pub fn acquire(this: *ThreadSafeFunction) !void {
@@ -1415,6 +1415,7 @@ pub export fn napi_create_threadsafe_function(
         .ctx = context,
         .channel = ThreadSafeFunction.Queue.init(max_queue_size, bun.default_allocator),
         .owning_threads = .{},
+        .poll_ref = JSC.PollRef.init(),
     };
     function.owning_threads.ensureTotalCapacity(bun.default_allocator, initial_thread_count) catch return genericFailure();
     function.finalizer = .{ .ctx = thread_finalize_data, .fun = thread_finalize_cb };