src: add Env::AddCleanupHook

doc/env.md

@@ -130,3 +130,67 @@ Associates a data item stored at `T* data` with the current instance of the
 addon. The item will be passed to the function `fini` which gets called when an
 instance of the addon is unloaded. This overload accepts an additional hint to
 be passed to `fini`.
+
+### AddCleanupHook
+
+```cpp
+template <typename Hook>
+CleanupHook<Hook> AddCleanupHook(Hook hook);
+```
+
+- `[in] hook`: A function to call when the environment exists. Accepts a
+  function of the form `void ()`.
+
+Registers `hook` as a function to be run once the current Node.js environment
+exits. Unlike the underlying C-based Node-API, providing the same `hook`
+multiple times **is** allowed. The hooks will be called in reverse order, i.e.
+the most recently added one will be called first.
+
+Returns an `Env::CleanupHook` object, which can be used to remove the hook via
+its `Remove()` method.
+
+### AddCleanupHook
+
+```cpp
+template <typename Hook, typename Arg>
+CleanupHook<Hook, Arg> AddCleanupHook(Hook hook, Arg* arg);
+```
+
+- `[in] hook`: A function to call when the environment exists. Accepts a
+  function of the form `void (Arg* arg)`.
+- `[in] arg`: A pointer to data that will be passed as the argument to `hook`.
+
+Registers `hook` as a function to be run with the `arg` parameter once the
+current Node.js environment exits. Unlike the underlying C-based Node-API,
+providing the same `hook` and `arg` pair multiple times **is** allowed. The
+hooks will be called in reverse order, i.e. the most recently added one will be
+called first.
+
+Returns an `Env::CleanupHook` object, which can be used to remove the hook via
+its `Remove()` method.
+
+# Env::CleanupHook
+
+The `Env::CleanupHook` object allows removal of the hook added via
+`Env::AddCleanupHook()`
+
+## Methods
+
+### IsEmpty
+
+```cpp
+bool IsEmpty();
+```
+
+Returns `true` if the cleanup hook was **not** successfully registered.
+
+### Remove
+
+```cpp
+bool Remove(Env env);
+```
+
+Unregisters the hook from running once the current Node.js environment exits.
+
+Returns `true` if the hook was successfully removed from the Node.js
+environment.

napi-inl.h

@@ -442,6 +442,26 @@ inline Value Env::RunScript(String script) {
   return Value(_env, result);
 }
 
+#if NAPI_VERSION > 2
+template <typename Hook, typename Arg>
+void Env::CleanupHook<Hook, Arg>::Wrapper(void* data) NAPI_NOEXCEPT {
+  auto* cleanupData =
+      static_cast<typename Napi::Env::CleanupHook<Hook, Arg>::CleanupData*>(
+          data);
+  cleanupData->hook();
+  delete cleanupData;
+}
+
+template <typename Hook, typename Arg>
+void Env::CleanupHook<Hook, Arg>::WrapperWithArg(void* data) NAPI_NOEXCEPT {
+  auto* cleanupData =
+      static_cast<typename Napi::Env::CleanupHook<Hook, Arg>::CleanupData*>(
+          data);
+  cleanupData->hook(static_cast<Arg*>(cleanupData->arg));
+  delete cleanupData;
+}
+#endif  // NAPI_VERSION > 2
+
 #if NAPI_VERSION > 5
 template <typename T, Env::Finalizer<T> fini>
 inline void Env::SetInstanceData(T* data) {
@@ -5692,6 +5712,53 @@ Addon<T>::DefineProperties(Object object,
 }
 #endif  // NAPI_VERSION > 5
 
+#if NAPI_VERSION > 2
+template <typename Hook, typename Arg>
+Env::CleanupHook<Hook, Arg> Env::AddCleanupHook(Hook hook, Arg* arg) {
+  return CleanupHook<Hook, Arg>(*this, hook, arg);
+}
+
+template <typename Hook>
+Env::CleanupHook<Hook> Env::AddCleanupHook(Hook hook) {
+  return CleanupHook<Hook>(*this, hook);
+}
+
+template <typename Hook, typename Arg>
+Env::CleanupHook<Hook, Arg>::CleanupHook(Napi::Env env, Hook hook)
+    : wrapper(Env::CleanupHook<Hook, Arg>::Wrapper) {
+  data = new CleanupData{std::move(hook), nullptr};
+  napi_status status = napi_add_env_cleanup_hook(env, wrapper, data);
+  if (status != napi_ok) {
+    delete data;
+    data = nullptr;
+  }
+}
+
+template <typename Hook, typename Arg>
+Env::CleanupHook<Hook, Arg>::CleanupHook(Napi::Env env, Hook hook, Arg* arg)
+    : wrapper(Env::CleanupHook<Hook, Arg>::WrapperWithArg) {
+  data = new CleanupData{std::move(hook), arg};
+  napi_status status = napi_add_env_cleanup_hook(env, wrapper, data);
+  if (status != napi_ok) {
+    delete data;
+    data = nullptr;
+  }
+}
+
+template <class Hook, class Arg>
+bool Env::CleanupHook<Hook, Arg>::Remove(Env env) {
+  napi_status status = napi_remove_env_cleanup_hook(env, wrapper, data);
+  delete data;
+  data = nullptr;
+  return status == napi_ok;
+}
+
+template <class Hook, class Arg>
+bool Env::CleanupHook<Hook, Arg>::IsEmpty() const {
+  return data == nullptr;
+}
+#endif  // NAPI_VERSION > 2
+
 } // namespace Napi
 
 #endif // SRC_NAPI_INL_H_

napi.h

@@ -179,8 +179,12 @@ namespace Napi {
   /// In the V8 JavaScript engine, a Node-API environment approximately
   /// corresponds to an Isolate.
   class Env {
+   private:
+#if NAPI_VERSION > 2
+    template <typename Hook, typename Arg = void>
+    class CleanupHook;
+#endif  // NAPI_VERSION > 2
 #if NAPI_VERSION > 5
-  private:
     template <typename T> static void DefaultFini(Env, T* data);
     template <typename DataType, typename HintType>
     static void DefaultFiniWithHint(Env, DataType* data, HintType* hint);
@@ -201,6 +205,14 @@ namespace Napi {
     Value RunScript(const std::string& utf8script);
     Value RunScript(String script);
 
+#if NAPI_VERSION > 2
+    template <typename Hook>
+    CleanupHook<Hook> AddCleanupHook(Hook hook);
+
+    template <typename Hook, typename Arg>
+    CleanupHook<Hook, Arg> AddCleanupHook(Hook hook, Arg* arg);
+#endif  // NAPI_VERSION > 2
+
 #if NAPI_VERSION > 5
     template <typename T> T* GetInstanceData();
 
@@ -219,7 +231,28 @@ namespace Napi {
 
   private:
     napi_env _env;
+
+#if NAPI_VERSION > 2
+    template <typename Hook, typename Arg>
+    class CleanupHook {
+     public:
+      CleanupHook(Env env, Hook hook, Arg* arg);
+      CleanupHook(Env env, Hook hook);
+      bool Remove(Env env);
+      bool IsEmpty() const;
+
+     private:
+      static inline void Wrapper(void* data) NAPI_NOEXCEPT;
+      static inline void WrapperWithArg(void* data) NAPI_NOEXCEPT;
+
+      void (*wrapper)(void* arg);
+      struct CleanupData {
+        Hook hook;
+        Arg* arg;
+      } * data;
+    };
   };
+#endif  // NAPI_VERSION > 2
 
   /// A JavaScript value of unknown type.
   ///

test/binding.cc

@@ -30,6 +30,7 @@ Object InitDate(Env env);
 #endif
 Object InitDataView(Env env);
 Object InitDataViewReadWrite(Env env);
+Object InitEnvCleanup(Env env);
 Object InitError(Env env);
 Object InitExternal(Env env);
 Object InitFunction(Env env);
@@ -103,6 +104,7 @@ Object Init(Env env, Object exports) {
   exports.Set("dataview", InitDataView(env));
   exports.Set("dataview_read_write", InitDataView(env));
   exports.Set("dataview_read_write", InitDataViewReadWrite(env));
+  exports.Set("env_cleanup", InitEnvCleanup(env));
   exports.Set("error", InitError(env));
   exports.Set("external", InitExternal(env));
   exports.Set("function", InitFunction(env));

test/binding.gyp

@@ -22,6 +22,7 @@
         'callbackscope.cc',
         'dataview/dataview.cc',
         'dataview/dataview_read_write.cc',
+        'env_cleanup.cc',
         'error.cc',
         'external.cc',
         'function.cc',

test/env_cleanup.cc

@@ -0,0 +1,81 @@
+#include <stdio.h>
+#include "napi.h"
+
+using namespace Napi;
+
+static void cleanup(void* arg) {
+  printf("static cleanup(%d)\n", *(int*)(arg));
+}
+static void cleanupInt(int* arg) {
+  printf("static cleanup(%d)\n", *(arg));
+}
+
+static void cleanupVoid() {
+  printf("static cleanup()\n");
+}
+
+static int secret1 = 42;
+static int secret2 = 43;
+
+Value AddHooks(const CallbackInfo& info) {
+  auto env = info.Env();
+
+  bool shouldRemove = info[0].As<Boolean>().Value();
+
+  // hook: void (*)(void *arg), hint: int
+  auto hook1 = env.AddCleanupHook(cleanup, &secret1);
+  // test using same hook+arg pair
+  auto hook1b = env.AddCleanupHook(cleanup, &secret1);
+
+  // hook: void (*)(int *arg), hint: int
+  auto hook2 = env.AddCleanupHook(cleanupInt, &secret2);
+
+  // hook: void (*)(int *arg), hint: void (default)
+  auto hook3 = env.AddCleanupHook(cleanupVoid);
+  // test using the same hook
+  auto hook3b = env.AddCleanupHook(cleanupVoid);
+
+  // hook: lambda []void (int *arg)->void, hint: int
+  auto hook4 = env.AddCleanupHook(
+      [&](int* arg) { printf("lambda cleanup(%d)\n", *arg); }, &secret1);
+
+  // hook: lambda []void (void *)->void, hint: void
+  auto hook5 =
+      env.AddCleanupHook([&](void*) { printf("lambda cleanup(void)\n"); },
+                         static_cast<void*>(nullptr));
+
+  // hook: lambda []void ()->void, hint: void (default)
+  auto hook6 = env.AddCleanupHook([&]() { printf("lambda cleanup()\n"); });
+
+  if (shouldRemove) {
+    hook1.Remove(env);
+    hook1b.Remove(env);
+    hook2.Remove(env);
+    hook3.Remove(env);
+    hook3b.Remove(env);
+    hook4.Remove(env);
+    hook5.Remove(env);
+    hook6.Remove(env);
+  }
+
+  int added = 0;
+
+  added += !hook1.IsEmpty();
+  added += !hook1b.IsEmpty();
+  added += !hook2.IsEmpty();
+  added += !hook3.IsEmpty();
+  added += !hook3b.IsEmpty();
+  added += !hook4.IsEmpty();
+  added += !hook5.IsEmpty();
+  added += !hook6.IsEmpty();
+
+  return Number::New(env, added);
+}
+
+Object InitEnvCleanup(Env env) {
+  Object exports = Object::New(env);
+
+  exports["addHooks"] = Function::New(env, AddHooks);
+
+  return exports;
+}

test/env_cleanup.js

@@ -0,0 +1,57 @@
+'use strict';
+
+const assert = require('assert');
+
+if (process.argv[2] === 'runInChildProcess') {
+    const binding_path = process.argv[3];
+    const remove_hooks = process.argv[4] === 'true';
+
+    const binding = require(binding_path);
+    const actualAdded = binding.env_cleanup.addHooks(remove_hooks);
+    const expectedAdded = remove_hooks === true ? 0 : 8;
+    assert(actualAdded === expectedAdded, 'Incorrect number of hooks added');
+}
+else {
+    module.exports = require('./common').runTestWithBindingPath(test);
+}
+
+function test(bindingPath) {
+    for (const remove_hooks of [false, true]) {
+        const { status, output } = require('./napi_child').spawnSync(
+            process.execPath,
+            [
+                __filename,
+                'runInChildProcess',
+                bindingPath,
+                remove_hooks,
+            ],
+            { encoding: 'utf8' }
+        );
+
+        const stdout = output[1].trim();
+        /**
+         * There is no need to sort the lines, as per Node-API documentation:
+         *  > The hooks will be called in reverse order, i.e. the most recently
+         *  > added one will be called first.
+        */
+        const lines = stdout.split(/[\r\n]+/);
+
+        assert(status === 0, `Process aborted with status ${status}`);
+
+        if (remove_hooks) {
+            assert.deepStrictEqual(lines, [''], 'Child process had console output when none expected')
+        } else {
+            assert.deepStrictEqual(lines, [
+                'lambda cleanup()',
+                'lambda cleanup(void)',
+                'lambda cleanup(42)',
+                'static cleanup()',
+                'static cleanup()',
+                'static cleanup(43)',
+                'static cleanup(42)',
+                'static cleanup(42)'
+            ],  'Child process console output mismisatch')
+        }
+    }
+}
+