node-api: document node-api shutdown finalization

As status quo, the cleanup hooks are invoked before the `napi_finalize`
callbacks at the exit of Node.js environments. This gives addons a
chance to release their resource in a proper order manually.

Document this behavior explicitly to advocate the usage on cleanup
hooks instead of relying on the implied invocation of `napi_finalize`
callbacks at shutdown.

PR-URL: #45903
Fixes: #45088
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Michael Dawson <midawson@redhat.com>

doc/api/n-api.md

@@ -478,11 +478,11 @@ may be called multiple times, from multiple contexts, and even concurrently from
 multiple threads.
 
 Native addons may need to allocate global state which they use during
-their entire life cycle such that the state must be unique to each instance of
-the addon.
+their life cycle of an Node.js environment such that the state can be
+unique to each instance of the addon.
 
-To this end, Node-API provides a way to allocate data such that its life cycle
-is tied to the life cycle of the Agent.
+To this end, Node-API provides a way to associate data such that its life cycle
+is tied to the life cycle of a Node.js environment.
 
 ### `napi_set_instance_data`
 
@@ -510,11 +510,11 @@ napi_status napi_set_instance_data(napi_env env,
 
 Returns `napi_ok` if the API succeeded.
 
-This API associates `data` with the currently running Agent. `data` can later
-be retrieved using `napi_get_instance_data()`. Any existing data associated with
-the currently running Agent which was set by means of a previous call to
-`napi_set_instance_data()` will be overwritten. If a `finalize_cb` was provided
-by the previous call, it will not be called.
+This API associates `data` with the currently running Node.js environment. `data`
+can later be retrieved using `napi_get_instance_data()`. Any existing data
+associated with the currently running Node.js environment which was set by means
+of a previous call to `napi_set_instance_data()` will be overwritten. If a
+`finalize_cb` was provided by the previous call, it will not be called.
 
 ### `napi_get_instance_data`
 
@@ -532,13 +532,13 @@ napi_status napi_get_instance_data(napi_env env,
 
 * `[in] env`: The environment that the Node-API call is invoked under.
 * `[out] data`: The data item that was previously associated with the currently
-  running Agent by a call to `napi_set_instance_data()`.
+  running Node.js environment by a call to `napi_set_instance_data()`.
 
 Returns `napi_ok` if the API succeeded.
 
 This API retrieves data that was previously associated with the currently
-running Agent via `napi_set_instance_data()`. If no data is set, the call will
-succeed and `data` will be set to `NULL`.
+running Node.js environment via `napi_set_instance_data()`. If no data is set,
+the call will succeed and `data` will be set to `NULL`.
 
 ## Basic Node-API data types
 
@@ -1799,11 +1799,11 @@ If still valid, this API returns the `napi_value` representing the
 JavaScript `Object` associated with the `napi_ref`. Otherwise, result
 will be `NULL`.
 
-### Cleanup on exit of the current Node.js instance
+### Cleanup on exit of the current Node.js environment
 
 While a Node.js process typically releases all its resources when exiting,
 embedders of Node.js, or future Worker support, may require addons to register
-clean-up hooks that will be run once the current Node.js instance exits.
+clean-up hooks that will be run once the current Node.js environment exits.
 
 Node-API provides functions for registering and un-registering such callbacks.
 When those callbacks are run, all resources that are being held by the addon
@@ -1929,6 +1929,22 @@ the hook from being executed, unless it has already started executing.
 This must be called on any `napi_async_cleanup_hook_handle` value obtained
 from [`napi_add_async_cleanup_hook`][].
 
+### Finalization on the exit of the Node.js environment
+
+The Node.js environment may be torn down at an arbitrary time as soon as
+possible with JavaScript execution disallowed, like on the request of
+[`worker.terminate()`][]. When the environment is being torn down, the
+registered `napi_finalize` callbacks of JavaScript objects, Thread-safe
+functions and environment instance data are invoked immediately and
+independently.
+
+The invocation of `napi_finalize` callbacks are scheduled after the manually
+registered cleanup hooks. In order to ensure a proper order of addon
+finalization during environment shutdown to avoid use-after-free in the
+`napi_finalize` callback, addons should register a cleanup hook with
+`napi_add_env_cleanup_hook` and `napi_add_async_cleanup_hook` to manually
+release the allocated resource in a proper order.
+
 ## Module registration
 
 Node-API modules are registered in a manner similar to other modules
@@ -6433,6 +6449,7 @@ the add-on's file name during loading.
 [`process.release`]: process.md#processrelease
 [`uv_ref`]: https://docs.libuv.org/en/v1.x/handle.html#c.uv_ref
 [`uv_unref`]: https://docs.libuv.org/en/v1.x/handle.html#c.uv_unref
+[`worker.terminate()`]: worker_threads.md#workerterminate
 [async_hooks `type`]: async_hooks.md#type
 [context-aware addons]: addons.md#context-aware-addons
 [docs]: https://github.com/nodejs/node-addon-api#api-documentation