Fix #1943

src/bin.ts

@@ -630,7 +630,7 @@ function phase4(payload: BootstrapState) {
   if (executeEntrypoint) {
     if (
       payload.isInChildProcess &&
-      versionGteLt(process.versions.node, '18.6.0')
+      versionGteLt(process.versions.node, '18.6.0', '18.7.0')
     ) {
       // HACK workaround node regression
       require('../dist-raw/runmain-hack.js').run(entryPointPath);

src/esm.ts

@@ -6,7 +6,7 @@ import {
   fileURLToPath,
   pathToFileURL,
 } from 'url';
-import { extname } from 'path';
+import { extname, resolve as pathResolve } from 'path';
 import * as assert from 'assert';
 import { normalizeSlashes, versionGteLt } from './util';
 import { createRequire } from 'module';
@@ -137,12 +137,19 @@ export function createEsmHooks(tsNodeService: Service) {
     return protocol === null || protocol === 'file:';
   }
 
+  const runMainHackUrl = pathToFileURL(
+    pathResolve(__dirname, '../dist-raw/runmain-hack.js')
+  ).toString();
+
   /**
    * Named "probably" as a reminder that this is a guess.
    * node does not explicitly tell us if we're resolving the entrypoint or not.
    */
   function isProbablyEntrypoint(specifier: string, parentURL: string) {
-    return parentURL === undefined && specifier.startsWith('file://');
+    return (
+      (parentURL === undefined || parentURL === runMainHackUrl) &&
+      specifier.startsWith('file://')
+    );
   }
   // Side-channel between `resolve()` and `load()` hooks
   const rememberIsProbablyEntrypoint = new Set();

src/test/esm-loader.spec.ts

@@ -336,6 +336,14 @@ test.suite('esm', (test) => {
       });
     }
 
+    test('extensionless entrypoint, regression test for #1943', async (t) => {
+      const { err, stdout } = await exec(
+        `${BIN_ESM_PATH} ./esm-loader-entrypoint-cjs-fallback/extensionless-entrypoint`
+      );
+      expect(err).toBe(null);
+      expect(stdout.trim()).toBe('Hello world!');
+    });
+
     test.suite('parent passes signals to child', (test) => {
       signalTest('SIGINT');
       signalTest('SIGTERM');