src: introduce convenience node::MakeSyncCallback()

There are situations where one wants to invoke a JS callback's ->Call()
from C++ and in particular retain any existing async_context state, but
where it's not obvious that a plain ->Call() would be safe at the point
in question.

Such callsites usually resort to
node::MakeCallback(..., async_context{0, 0}), which unconditionally
pushes the async_context{0, 0} and takes the required provisions for the
->Call() itself such as triggering the tick after its return, if needed.

An example would be the PerformanceObserver invocation from
PerformanceEntry::Notify(): this can get called when coming from JS
through e.g. perf_hooks.performance.mark() and alike, but perhaps also
from nghttp2 (c.f. EmitStatistics() in node_http2.cc).

In the former case, a plain ->Call() would be safe and it would be
desirable to retain the current async_context so that
PerformanceObservers can access it resp. the associated
AsyncLocalStorage. However, in the second case the additional provisions
taken by node::MakeCallback() might potentially be strictly required.

So PerformanceEntry::Notify() bites the bullet and invokes the
PerformanceObservers through node::MakeCallback() unconditionally,
thereby always rendering any possibly preexisting async_context
inaccessible.

Introduce the convenience node::MakeSyncCallback() for such usecases,
which would basically forward to ->Call() if safe and to
node::MakeCallback(..., async_context{0, 0}) otherwise.

Co-Authored-By: ZauberNerd <zaubernerd@zaubernerd.de>

PR-URL: https://github.com/nodejs/node/pull/36343
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Rich Trott <rtrott@gmail.com>

1 files changed, 6 insertions, 0 deletions

diff --git a/src/node_internals.h b/src/node_internals.h
index f7a1e2d8d62..b75092d662d 100644
--- a/src/node_internals.h
+++ b/src/node_internals.h
@@ -200,6 +200,12 @@ v8::MaybeLocal<v8::Value> InternalMakeCallback(
     v8::Local<v8::Value> argv[],
     async_context asyncContext);
 
+v8::MaybeLocal<v8::Value> MakeSyncCallback(v8::Isolate* isolate,
+                                           v8::Local<v8::Object> recv,
+                                           v8::Local<v8::Function> callback,
+                                           int argc,
+                                           v8::Local<v8::Value> argv[]);
+
 class InternalCallbackScope {
  public:
   enum Flags {