process: allow StartExecution() to take a main script ID

The idea is to allow the C++ layer to run arbitrary scripts
as the main script. This paves the way for

- cctest of the execution of Node.js instances
- Earlier handling of per-process CLI options that affect
  execution modes (those usually do not make sense for the
  embedders).
- Targets like mkcodecache or mksnapshot.

Also moves the handling of `_third_party_main.js` into C++.

PR-URL: https://github.com/nodejs/node/pull/25474
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Minwoo Jung <minwoo@nodesource.com>

1 files changed, 4 insertions, 0 deletions

diff --git a/src/node_native_module.cc b/src/node_native_module.cc
index 1b1a5e8ec1..00775885d6 100644
--- a/src/node_native_module.cc
+++ b/src/node_native_module.cc
@@ -61,6 +61,10 @@ Local<Set> ToJsSet(Local<Context> context,
   return out;
 }
 
+bool NativeModuleLoader::Exists(const char* id) {
+  return source_.find(id) != source_.end();
+}
+
 void NativeModuleLoader::GetCacheUsage(
     const FunctionCallbackInfo<Value>& args) {
   Environment* env = Environment::GetCurrent(args);