src: split ownsProcessState off isMainThread

Embedders may want to control whether a Node.js instance
controls the current process, similar to what we currently
have with `Worker`s.

Previously, the `isMainThread` flag had a bit of a double usage,
both for indicating whether we are (not) running a Worker and
whether we can modify per-process state.

PR-URL: https://github.com/nodejs/node/pull/25881
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Joyee Cheung <joyeec9h3@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>

3 files changed, 10 insertions, 8 deletions

diff --git a/lib/internal/bootstrap/node.js b/lib/internal/bootstrap/node.js
index 915d07d83d..358c4cb8c7 100644
--- a/lib/internal/bootstrap/node.js
+++ b/lib/internal/bootstrap/node.js
@@ -14,7 +14,7 @@
 
 // This file is compiled as if it's wrapped in a function with arguments
 // passed by node::LoadEnvironment()
-/* global process, loaderExports, isMainThread */
+/* global process, loaderExports, isMainThread, ownsProcessState */
 
 const { internalBinding, NativeModule } = loaderExports;
 
@@ -51,7 +51,7 @@ const perThreadSetup = NativeModule.require('internal/process/per_thread');
 let mainThreadSetup;
 // Bootstrappers for the worker threads only
 let workerThreadSetup;
-if (isMainThread) {
+if (ownsProcessState) {
   mainThreadSetup = NativeModule.require(
     'internal/process/main_thread_only'
   );
@@ -140,7 +140,7 @@ if (credentials.implementsPosixCredentials) {
   process.getegid = credentials.getegid;
   process.getgroups = credentials.getgroups;
 
-  if (isMainThread) {
+  if (ownsProcessState) {
     const wrapped = mainThreadSetup.wrapPosixCredentialSetters(credentials);
     process.initgroups = wrapped.initgroups;
     process.setgroups = wrapped.setgroups;
diff --git a/lib/internal/worker.js b/lib/internal/worker.js
index f28f4cd663..1d1a5e7d22 100644
--- a/lib/internal/worker.js
+++ b/lib/internal/worker.js
@@ -30,9 +30,10 @@ const { deserializeError } = require('internal/error-serdes');
 const { pathToFileURL } = require('url');
 
 const {
-  Worker: WorkerImpl,
+  ownsProcessState,
+  isMainThread,
   threadId,
-  isMainThread
+  Worker: WorkerImpl,
 } = internalBinding('worker');
 
 const kHandle = Symbol('kHandle');
@@ -243,7 +244,8 @@ function pipeWithoutWarning(source, dest) {
 }
 
 module.exports = {
+  ownsProcessState,
+  isMainThread,
   threadId,
   Worker,
-  isMainThread
 };
diff --git a/lib/trace_events.js b/lib/trace_events.js
index d2977679e1..41c4dbe741 100644
--- a/lib/trace_events.js
+++ b/lib/trace_events.js
@@ -13,8 +13,8 @@ const {
   ERR_INVALID_ARG_TYPE
 } = require('internal/errors').codes;
 
-const { isMainThread } = require('internal/worker');
-if (!hasTracing || !isMainThread)
+const { ownsProcessState } = require('internal/worker');
+if (!hasTracing || !ownsProcessState)
   throw new ERR_TRACE_EVENTS_UNAVAILABLE();
 
 const { CategorySet, getEnabledCategories } = internalBinding('trace_events');