module: reduce circular dependency of internal/modules/cjs/loader

Previously `internal/bootstrap/pre_execution.js` requires
`internal/modules/cjs/loader.js` which in turn requires
`internal/bootstrap/pre_execution.js`. This patch moves the
entry point execution logic out of `pre_execution.js` and
puts it into `internal/modules/run_main.js`. It also tests
that `Module.runMain` can be monkey-patched before further
deprecation/refactoring can be done.

Also added an internal assertion `hasLoadedAnyUserCJSModule`
for documentation purposes.

PR-URL: https://github.com/nodejs/node/pull/30349
Reviewed-By: Guy Bedford <guybedford@gmail.com>
Reviewed-By: James M Snell <jasnell@gmail.com>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

2 files changed, 12 insertions, 6 deletions

diff --git a/lib/internal/main/run_main_module.js b/lib/internal/main/run_main_module.js
index eae9042041a..ca5d1122c59 100644
--- a/lib/internal/main/run_main_module.js
+++ b/lib/internal/main/run_main_module.js
@@ -6,10 +6,12 @@ const {
 
 prepareMainThreadExecution(true);
 
-const CJSModule = require('internal/modules/cjs/loader').Module;
-
 markBootstrapComplete();
 
 // Note: this loads the module through the ESM loader if the module is
-// determined to be an ES module
-CJSModule.runMain(process.argv[1]);
+// determined to be an ES module. This hangs from the CJS module loader
+// because we currently allow monkey-patching of the module loaders
+// in the preloaded scripts through require('module').
+// runMain here might be monkey-patched by users in --require.
+// XXX: the monkey-patchability here should probably be deprecated.
+require('internal/modules/cjs/loader').Module.runMain(process.argv[1]);
diff --git a/lib/internal/main/worker_thread.js b/lib/internal/main/worker_thread.js
index 7cf8ffb8b40..13d7e8de0ec 100644
--- a/lib/internal/main/worker_thread.js
+++ b/lib/internal/main/worker_thread.js
@@ -108,6 +108,9 @@ port.on('message', (message) => {
     initializeDeprecations();
     initializeCJSLoader();
     initializeESMLoader();
+
+    const CJSLoader = require('internal/modules/cjs/loader');
+    assert(!CJSLoader.hasLoadedAnyUserCJSModule);
     loadPreloadModules();
     initializeFrozenIntrinsics();
     publicWorker.parentPort = publicPort;
@@ -141,8 +144,9 @@ port.on('message', (message) => {
       evalScript('[worker eval]', filename);
     } else {
       // script filename
-      const CJSModule = require('internal/modules/cjs/loader').Module;
-      CJSModule.runMain(process.argv[1] = filename);
+      // runMain here might be monkey-patched by users in --require.
+      // XXX: the monkey-patchability here should probably be deprecated.
+      CJSLoader.Module.runMain(process.argv[1] = filename);
     }
   } else if (message.type === STDIO_PAYLOAD) {
     const { stream, chunk, encoding } = message;