module: prevent race condition while combining import and require

This checks if any require calls have happened to the same file
during the file read. If that was the case, it'll return the same
module instead of creating a new instance.

PR-URL: https://github.com/nodejs/node/pull/27674
Reviewed-By: Guy Bedford <guybedford@gmail.com>

1 files changed, 10 insertions, 0 deletions

diff --git a/lib/internal/modules/esm/translators.js b/lib/internal/modules/esm/translators.js
index 9526e05263..b1f2c9f259 100644
--- a/lib/internal/modules/esm/translators.js
+++ b/lib/internal/modules/esm/translators.js
@@ -123,6 +123,16 @@ translators.set('json', async function jsonStrategy(url) {
     });
   }
   const content = await readFileAsync(pathname, 'utf-8');
+  // A require call could have been called on the same file during loading and
+  // that resolves synchronously. To make sure we always return the identical
+  // export, we have to check again if the module already exists or not.
+  module = CJSModule._cache[modulePath];
+  if (module && module.loaded) {
+    const exports = module.exports;
+    return createDynamicModule(['default'], url, (reflect) => {
+      reflect.exports.default.set(exports);
+    });
+  }
   try {
     const exports = JsonParse(stripBOM(content));
     module = {