module: do not use process.exit()

lib/internal/modules/cjs/loader.js

@@ -794,9 +794,13 @@ Module.runMain = function() {
       return loader.import(pathToFileURL(process.argv[1]).pathname);
     })
     .catch((e) => {
+      // TODO(addaleax): This should, ideally, trigger a fatal exception
+      // instead. That should alread be doable for code in core now, but it's
+      // probably easier to wait until something like
+      // https://github.com/nodejs/node/pull/25715 lands?
       decorateErrorStack(e);
       console.error(e);
-      process.exit(1);
+      process.exitCode = 1;
     });
   } else {
     Module._load(process.argv[1], null, true);

lib/internal/modules/esm/module_job.js

@@ -6,6 +6,8 @@ const { decorateErrorStack } = require('internal/util');
 const assert = require('assert');
 const resolvedPromise = SafePromise.resolve();
 
+function noop() {}
+
 /* A ModuleJob tracks the loading of a single Module, and the ModuleJobs of
  * its dependencies, over time. */
 class ModuleJob {
@@ -41,6 +43,9 @@ class ModuleJob {
     };
     // Promise for the list of all dependencyJobs.
     this.linked = link();
+    // This promise is awaited later anyway, so silence
+    // 'unhandled rejection' warnings.
+    this.linked.catch(noop);
 
     // instantiated == deep dependency jobs wrappers instantiated,
     // module wrapper instantiated

test/parallel/test-worker-esm-missing-main.js

@@ -0,0 +1,17 @@
+'use strict';
+const common = require('../common');
+const assert = require('assert');
+const { Worker } = require('worker_threads');
+
+const worker = new Worker('./does-not-exist.js', {
+  execArgv: ['--experimental-modules'],
+  stderr: true
+});
+
+let stderr = '';
+worker.stderr.setEncoding('utf8');
+worker.stderr.on('data', (chunk) => stderr += chunk);
+worker.stderr.on('end', common.mustCall(() => {
+  // eslint-disable-next-line node-core/no-unescaped-regexp-dot
+  assert(/Cannot find module .+does-not-exist.js/.test(stderr), stderr);
+}));