n-api: add APIs for per-instance state management

Adds `napi_set_instance_data()` and `napi_get_instance_data()`, which
allow native addons to store their data on and retrieve their data from
`napi_env`. `napi_set_instance_data()` accepts a finalizer which is
called when the `node::Environment()` is destroyed.

This entails rendering the `napi_env` local to each add-on.

Fixes: https://github.com/nodejs/abi-stable-node/issues/378
PR-URL: https://github.com/nodejs/node/pull/28682
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Michael Dawson <michael_dawson@ca.ibm.com>

1 files changed, 23 insertions, 51 deletions

diff --git a/src/node_api.cc b/src/node_api.cc
index a9f26e551d..4947293063 100644
--- a/src/node_api.cc
+++ b/src/node_api.cc
@@ -46,9 +46,9 @@ class BufferFinalizer : private Finalizer {
         v8::HandleScope handle_scope(finalizer->_env->isolate);
         v8::Context::Scope context_scope(finalizer->_env->context());
 
-        NapiCallIntoModuleThrow(finalizer->_env, [&]() {
+        finalizer->_env->CallIntoModuleThrow([&](napi_env env) {
           finalizer->_finalize_callback(
-              finalizer->_env,
+              env,
               finalizer->_finalize_data,
               finalizer->_finalize_hint);
         });
@@ -59,44 +59,22 @@ class BufferFinalizer : private Finalizer {
   }
 };
 
-static inline napi_env GetEnv(v8::Local<v8::Context> context) {
+static inline napi_env NewEnv(v8::Local<v8::Context> context) {
   node_napi_env result;
 
-  auto isolate = context->GetIsolate();
-  auto global = context->Global();
-
-  // In the case of the string for which we grab the private and the value of
-  // the private on the global object we can call .ToLocalChecked() directly
-  // because we need to stop hard if either of them is empty.
-  //
-  // Re https://github.com/nodejs/node/pull/14217#discussion_r128775149
-  auto value = global->GetPrivate(context, NAPI_PRIVATE_KEY(context, env))
-      .ToLocalChecked();
-
-  if (value->IsExternal()) {
-    result = static_cast<node_napi_env>(value.As<v8::External>()->Value());
-  } else {
-    result = new node_napi_env__(context);
-    auto external = v8::External::New(isolate, result);
-
-    // We must also stop hard if the result of assigning the env to the global
-    // is either nothing or false.
-    CHECK(global->SetPrivate(context, NAPI_PRIVATE_KEY(context, env), external)
-        .FromJust());
-
-    // TODO(addaleax): There was previously code that tried to delete the
-    // napi_env when its v8::Context was garbage collected;
-    // However, as long as N-API addons using this napi_env are in place,
-    // the Context needs to be accessible and alive.
-    // Ideally, we'd want an on-addon-unload hook that takes care of this
-    // once all N-API addons using this napi_env are unloaded.
-    // For now, a per-Environment cleanup hook is the best we can do.
-    result->node_env()->AddCleanupHook(
-        [](void* arg) {
-          static_cast<napi_env>(arg)->Unref();
-        },
-        static_cast<void*>(result));
-  }
+  result = new node_napi_env__(context);
+  // TODO(addaleax): There was previously code that tried to delete the
+  // napi_env when its v8::Context was garbage collected;
+  // However, as long as N-API addons using this napi_env are in place,
+  // the Context needs to be accessible and alive.
+  // Ideally, we'd want an on-addon-unload hook that takes care of this
+  // once all N-API addons using this napi_env are unloaded.
+  // For now, a per-Environment cleanup hook is the best we can do.
+  result->node_env()->AddCleanupHook(
+      [](void* arg) {
+        static_cast<napi_env>(arg)->Unref();
+      },
+      static_cast<void*>(result));
 
   return result;
 }
@@ -325,7 +303,7 @@ class ThreadSafeFunction : public node::AsyncResource {
             v8::Local<v8::Function>::New(env->isolate, ref);
           js_callback = v8impl::JsValueFromV8LocalValue(js_cb);
         }
-        NapiCallIntoModuleThrow(env, [&]() {
+        env->CallIntoModuleThrow([&](napi_env env) {
           call_js_cb(env, js_callback, context, data);
         });
       }
@@ -346,7 +324,7 @@ class ThreadSafeFunction : public node::AsyncResource {
     v8::HandleScope scope(env->isolate);
     if (finalize_cb) {
       CallbackScope cb_scope(this);
-      NapiCallIntoModuleThrow(env, [&]() {
+      env->CallIntoModuleThrow([&](napi_env env) {
         finalize_cb(env, finalize_data, context);
       });
     }
@@ -481,10 +459,10 @@ void napi_module_register_by_symbol(v8::Local<v8::Object> exports,
 
   // Create a new napi_env for this module or reference one if a pre-existing
   // one is found.
-  napi_env env = v8impl::GetEnv(context);
+  napi_env env = v8impl::NewEnv(context);
 
   napi_value _exports;
-  NapiCallIntoModuleThrow(env, [&]() {
+  env->CallIntoModuleThrow([&](napi_env env) {
     _exports = init(env, v8impl::JsValueFromV8LocalValue(exports));
   });
 
@@ -889,15 +867,9 @@ class Work : public node::AsyncResource, public node::ThreadPoolWork {
 
     CallbackScope callback_scope(this);
 
-    // We have to back up the env here because the `NAPI_CALL_INTO_MODULE` macro
-    // makes use of it after the call into the module completes, but the module
-    // may have deallocated **this**, and along with it the place where _env is
-    // stored.
-    napi_env env = _env;
-
-    NapiCallIntoModule(env, [&]() {
-      _complete(_env, ConvertUVErrorCode(status), _data);
-    }, [env](v8::Local<v8::Value> local_err) {
+    _env->CallIntoModule([&](napi_env env) {
+      _complete(env, ConvertUVErrorCode(status), _data);
+    }, [](napi_env env, v8::Local<v8::Value> local_err) {
       // If there was an unhandled exception in the complete callback,
       // report it as a fatal exception. (There is no JavaScript on the
       // callstack that can possibly handle it.)