module: fix cyclical dynamic import

ensures that instantiation result is only used during initial loading

Author: bmeck

lib/internal/loader/ModuleJob.js

@@ -53,10 +53,11 @@ class ModuleJob {
   }
 
   async instantiate() {
-    if (this.instantiated) {
-      return this.instantiated;
+    if (!this.instantiated) {
+      return this.instantiated = this._instantiate();
     }
-    return this.instantiated = this._instantiate();
+    await this.instantiated;
+    return this.module;
   }
 
   // This method instantiates the module associated with this job and its

test/es-module/test-esm-cyclic-dynamic-import.mjs

@@ -0,0 +1,3 @@
+// Flags: --experimental-modules
+import '../common';
+import('./test-esm-cyclic-dynamic-import');