Fix child module evaluation order

lib/Runtime/Language/SourceTextModuleRecord.cpp

@@ -1079,10 +1079,13 @@ namespace Js
 
         try
         {
-            if (childrenModuleSet != nullptr)
+            if (requestedModuleList != nullptr)
             {
-                childrenModuleSet->EachValue([=](SourceTextModuleRecord* childModuleRecord)
-                {
+                requestedModuleList->Reverse();
+                requestedModuleList->Map([&](IdentPtr specifier) {
+                    SourceTextModuleRecord* childModuleRecord = nullptr;
+                    AssertOrFailFast(childrenModuleSet->TryGetValue(specifier->Psz(), &childModuleRecord));
+
                     childModuleRecord->ModuleEvaluation();
                     // if child module was evaluated before and threw need to re-throw now
                     // if child module has been dynamically imported and has exception need to throw

test/es6module/module-bugfixes.js

@@ -94,6 +94,32 @@ var tests = [
             testRunner.LoadModule(start);
         }
     },
+    {
+        name: "Issue 6261: Specifier dependent module load order",
+        body: function() {
+            WScript.RegisterModuleSource("dep", `export const obj = {a:false, b: false, c: false};`);
+            WScript.RegisterModuleSource("one",`
+                import {obj} from "dep";
+                assert.isFalse(obj.b);
+                assert.isFalse(obj.c);
+                assert.isFalse(obj.a);
+                obj.a = true;`);
+            WScript.RegisterModuleSource("two",`
+                import {obj} from "dep";
+                assert.isFalse(obj.b);
+                assert.isFalse(obj.c);
+                assert.isTrue(obj.a);
+                obj.b = true;`);
+            WScript.RegisterModuleSource("three",`
+                import {obj} from "dep";
+                assert.isTrue(obj.b);
+                assert.isFalse(obj.c);
+                assert.isTrue(obj.a);
+                obj.c = true;`);
+            const start = 'import "one"; import "two"; import "three";';
+            testRunner.LoadModule(start);
+        }
+    },
     {
         // https://github.com/Microsoft/ChakraCore/issues/5501
         name : "Issue 5501: Indirect exports excluded from namespace object - POC 1",