fix: provide asynchronous cleanup hooks in n-api (#25281)

Co-authored-by: Shelley Vohr <shelley.vohr@gmail.com>

patches/node/.patches

@@ -43,3 +43,4 @@ fix_allow_preventing_setpromiserejectcallback.patch
 lib_use_non-symbols_in_isurlinstance_check.patch
 feat_add_implementation_of_v8_platform_postjob.patch
 fix_enable_tls_renegotiation.patch
+n-api_src_provide_asynchronous_cleanup_hooks.patch

patches/node/n-api_src_provide_asynchronous_cleanup_hooks.patch

@@ -0,0 +1,250 @@
+From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
+From: Shelley Vohr <shelley.vohr@gmail.com>
+Date: Tue, 25 Aug 2020 19:34:12 -0700
+Subject: n-api,src: provide asynchronous cleanup hooks
+
+Backports https://github.com/nodejs/node/pull/34572 and
+https://github.com/nodejs/node/pull/34819.
+
+Sometimes addons need to perform cleanup actions, for example
+closing libuv handles or waiting for requests to finish, that
+cannot be performed synchronously.
+
+Add C++ API and N-API functions that allow providing such
+asynchronous cleanup hooks.
+
+This patch can be removed when Electron upgrades to a version of Node.js
+which contains the above referenced commit(s).
+
+diff --git a/src/api/hooks.cc b/src/api/hooks.cc
+index 037bdda6f41c825dd112b0cc9fca0ebde47c6163..3b16c0350d8a8494202144407664af41d338fe04 100644
+--- a/src/api/hooks.cc
++++ b/src/api/hooks.cc
+@@ -73,8 +73,35 @@ int EmitExit(Environment* env) {
+       .ToChecked();
+ }
+
++typedef void (*CleanupHook)(void* arg);
++typedef void (*AsyncCleanupHook)(void* arg, void(*)(void*), void*);
++
++struct AsyncCleanupHookInfo final {
++  Environment* env;
++  AsyncCleanupHook fun;
++  void* arg;
++  bool started = false;
++  // Use a self-reference to make sure the storage is kept alive while the
++  // cleanup hook is registered but not yet finished.
++  std::shared_ptr<AsyncCleanupHookInfo> self;
++};
++
++// Opaque type that is basically an alias for `shared_ptr<AsyncCleanupHookInfo>`
++// (but not publicly so for easier ABI/API changes). In particular,
++// std::shared_ptr does not generally maintain a consistent ABI even on a
++// specific platform.
++struct ACHHandle final {
++  std::shared_ptr<AsyncCleanupHookInfo> info;
++};
++// This is implemented as an operator on a struct because otherwise you can't
++// default-initialize AsyncCleanupHookHandle, because in C++ for a
++// std::unique_ptr to be default-initializable the deleter type also needs
++// to be default-initializable; in particular, function types don't satisfy
++// this.
++void DeleteACHHandle::operator ()(ACHHandle* handle) const { delete handle; }
++
+ void AddEnvironmentCleanupHook(Isolate* isolate,
+-                               void (*fun)(void* arg),
++                               CleanupHook fun,
+                                void* arg) {
+   Environment* env = Environment::GetCurrent(isolate);
+   CHECK_NOT_NULL(env);
+@@ -82,13 +109,50 @@ void AddEnvironmentCleanupHook(Isolate* isolate,
+ }
+
+ void RemoveEnvironmentCleanupHook(Isolate* isolate,
+-                                  void (*fun)(void* arg),
++                                  CleanupHook fun,
+                                   void* arg) {
+   Environment* env = Environment::GetCurrent(isolate);
+   CHECK_NOT_NULL(env);
+   env->RemoveCleanupHook(fun, arg);
+ }
+
++static void FinishAsyncCleanupHook(void* arg) {
++  AsyncCleanupHookInfo* info = static_cast<AsyncCleanupHookInfo*>(arg);
++  std::shared_ptr<AsyncCleanupHookInfo> keep_alive = info->self;
++
++  info->env->DecreaseWaitingRequestCounter();
++  info->self.reset();
++}
++
++static void RunAsyncCleanupHook(void* arg) {
++  AsyncCleanupHookInfo* info = static_cast<AsyncCleanupHookInfo*>(arg);
++  info->env->IncreaseWaitingRequestCounter();
++  info->started = true;
++  info->fun(info->arg, FinishAsyncCleanupHook, info);
++}
++
++AsyncCleanupHookHandle AddEnvironmentCleanupHook(
++    Isolate* isolate,
++    AsyncCleanupHook fun,
++    void* arg) {
++  Environment* env = Environment::GetCurrent(isolate);
++  CHECK_NOT_NULL(env);
++  auto info = std::make_shared<AsyncCleanupHookInfo>();
++  info->env = env;
++  info->fun = fun;
++  info->arg = arg;
++  info->self = info;
++  env->AddCleanupHook(RunAsyncCleanupHook, info.get());
++  return AsyncCleanupHookHandle(new ACHHandle { info });
++}
++
++void RemoveEnvironmentCleanupHook(
++    AsyncCleanupHookHandle handle) {
++  if (handle->info->started) return;
++  handle->info->self.reset();
++  handle->info->env->RemoveCleanupHook(RunAsyncCleanupHook, handle->info.get());
++}
++
+ async_id AsyncHooksGetExecutionAsyncId(Isolate* isolate) {
+   Environment* env = Environment::GetCurrent(isolate);
+   if (env == nullptr) return -1;
+diff --git a/src/node.h b/src/node.h
+index 60ecc3bd3499c23b297bc11e7f052aede20520c2..4c4e55e338d7b42c36818a45f6b41170c495adde 100644
+--- a/src/node.h
++++ b/src/node.h
+@@ -739,6 +739,20 @@ NODE_EXTERN void RemoveEnvironmentCleanupHook(v8::Isolate* isolate,
+                                               void (*fun)(void* arg),
+                                               void* arg);
+
++/* These are async equivalents of the above. After the cleanup hook is invoked,
++ * `cb(cbarg)` *must* be called, and attempting to remove the cleanup hook will
++ * have no effect. */
++struct ACHHandle;
++struct NODE_EXTERN DeleteACHHandle { void operator()(ACHHandle*) const; };
++typedef std::unique_ptr<ACHHandle, DeleteACHHandle> AsyncCleanupHookHandle;
++
++NODE_EXTERN AsyncCleanupHookHandle AddEnvironmentCleanupHook(
++    v8::Isolate* isolate,
++    void (*fun)(void* arg, void (*cb)(void*), void* cbarg),
++    void* arg);
++
++NODE_EXTERN void RemoveEnvironmentCleanupHook(AsyncCleanupHookHandle holder);
++
+ /* Returns the id of the current execution context. If the return value is
+  * zero then no execution has been set. This will happen if the user handles
+  * I/O from native code. */
+diff --git a/src/node_api.cc b/src/node_api.cc
+index fe24eca1b8e2d81fbafd0a1e2da38d957fbaa1c1..66168bd2c28ce6481516e63734616f487e3ec3e1 100644
+--- a/src/node_api.cc
++++ b/src/node_api.cc
+@@ -507,6 +507,70 @@ napi_status napi_remove_env_cleanup_hook(napi_env env,
+   return napi_ok;
+ }
+
++struct napi_async_cleanup_hook_handle__ {
++  napi_async_cleanup_hook_handle__(napi_env env,
++                                   napi_async_cleanup_hook user_hook,
++                                   void* user_data):
++      env_(env),
++      user_hook_(user_hook),
++      user_data_(user_data) {
++    handle_ = node::AddEnvironmentCleanupHook(env->isolate, Hook, this);
++    env->Ref();
++  }
++
++  ~napi_async_cleanup_hook_handle__() {
++    node::RemoveEnvironmentCleanupHook(std::move(handle_));
++    if (done_cb_ != nullptr)
++      done_cb_(done_data_);
++
++    // Release the `env` handle asynchronously since it would be surprising if
++    // a call to a N-API function would destroy `env` synchronously.
++    static_cast<node_napi_env>(env_)->node_env()
++        ->SetImmediate([env = env_](node::Environment*) { env->Unref(); });
++  }
++
++  static void Hook(void* data, void (*done_cb)(void*), void* done_data) {
++    auto handle = static_cast<napi_async_cleanup_hook_handle__*>(data);
++    handle->done_cb_ = done_cb;
++    handle->done_data_ = done_data;
++    handle->user_hook_(handle, handle->user_data_);
++  }
++
++  node::AsyncCleanupHookHandle handle_;
++  napi_env env_ = nullptr;
++  napi_async_cleanup_hook user_hook_ = nullptr;
++  void* user_data_ = nullptr;
++  void (*done_cb_)(void*) = nullptr;
++  void* done_data_ = nullptr;
++};
++
++napi_status napi_add_async_cleanup_hook(
++    napi_env env,
++    napi_async_cleanup_hook hook,
++    void* arg,
++    napi_async_cleanup_hook_handle* remove_handle) {
++  CHECK_ENV(env);
++  CHECK_ARG(env, hook);
++
++  napi_async_cleanup_hook_handle__* handle =
++    new napi_async_cleanup_hook_handle__(env, hook, arg);
++
++  if (remove_handle != nullptr)
++    *remove_handle = handle;
++
++  return napi_clear_last_error(env);
++}
++
++napi_status napi_remove_async_cleanup_hook(
++    napi_async_cleanup_hook_handle remove_handle) {
++
++  if (remove_handle == nullptr)
++    return napi_invalid_arg;
++
++  delete remove_handle;
++  return napi_ok;
++}
++
+ napi_status napi_fatal_exception(napi_env env, napi_value err) {
+   NAPI_PREAMBLE(env);
+   CHECK_ARG(env, err);
+diff --git a/src/node_api.h b/src/node_api.h
+index 2f1b45572d8130f27492eb6188c1aa611f2e01a3..577a1dcd94987202819e7a36a2d9674f13d13614 100644
+--- a/src/node_api.h
++++ b/src/node_api.h
+@@ -250,6 +250,19 @@ napi_ref_threadsafe_function(napi_env env, napi_threadsafe_function func);
+
+ #endif  // NAPI_VERSION >= 4
+
++#ifdef NAPI_EXPERIMENTAL
++
++NAPI_EXTERN napi_status napi_add_async_cleanup_hook(
++    napi_env env,
++    napi_async_cleanup_hook hook,
++    void* arg,
++    napi_async_cleanup_hook_handle* remove_handle);
++
++NAPI_EXTERN napi_status napi_remove_async_cleanup_hook(
++    napi_async_cleanup_hook_handle remove_handle);
++
++#endif  // NAPI_EXPERIMENTAL
++
+ EXTERN_C_END
+
+ #endif  // SRC_NODE_API_H_
+diff --git a/src/node_api_types.h b/src/node_api_types.h
+index 1c9a2b8aa21889c0d29fb02b234ae9698d122c2c..0e400e9676df5ba09d350fe7a2a70a1dc9e4d3d6 100644
+--- a/src/node_api_types.h
++++ b/src/node_api_types.h
+@@ -41,4 +41,10 @@ typedef struct {
+   const char* release;
+ } napi_node_version;
+
++#ifdef NAPI_EXPERIMENTAL
++typedef struct napi_async_cleanup_hook_handle__* napi_async_cleanup_hook_handle;
++typedef void (*napi_async_cleanup_hook)(napi_async_cleanup_hook_handle handle,
++                                        void* data);
++#endif  // NAPI_EXPERIMENTAL
++
+ #endif  // SRC_NODE_API_TYPES_H_