From 96007eec2c0c380a48fc50c33f46269aac4c96ff Mon Sep 17 00:00:00 2001
From: "satish.srinivasan" <satish.srinivasan@servicenow.com>
Date: Thu, 12 Sep 2024 19:47:50 +0530
Subject: [PATCH] FIX: Evaluation of ?.

---
 .../org/mozilla/javascript/IRFactory.java     | 52 +++++++++++--------
 .../tests/NullishCoalescingOpTest.java        | 19 +++++++
 2 files changed, 49 insertions(+), 22 deletions(-)

diff --git a/rhino/src/main/java/org/mozilla/javascript/IRFactory.java b/rhino/src/main/java/org/mozilla/javascript/IRFactory.java
index 25faea2892..9733a7e205 100644
--- a/rhino/src/main/java/org/mozilla/javascript/IRFactory.java
+++ b/rhino/src/main/java/org/mozilla/javascript/IRFactory.java
@@ -758,7 +758,36 @@ private Node transformIf(IfStatement n) {
     private Node transformInfix(InfixExpression node) {
         Node left = transform(node.getLeft());
         Node right = transform(node.getRight());
-        return createBinary(node.getType(), left, right);
+        if (node.getType() == Token.NULLISH_COALESCING) {
+            return transformNullishCoalescing(left, right, node);
+        } else {
+            return createBinary(node.getType(), left, right);
+        }
+    }
+
+    private Node transformNullishCoalescing(Node left, Node right, Node parent) {
+        String tempName = parser.currentScriptOrFn.getNextTempName();
+
+        Node nullNode = new Node(Token.NULL);
+        Node undefinedNode = new Name(0, "undefined");
+
+        Node conditional =
+                new Node(
+                        Token.OR,
+                        new Node(Token.SHEQ, nullNode, parser.createName(tempName)),
+                        new Node(Token.SHEQ, undefinedNode, parser.createName(tempName)));
+
+        Node hookNode =
+                new Node(
+                        Token.HOOK,
+                        /* left= */ conditional,
+                        /* mid= */ right,
+                        /* right= */ parser.createName(tempName));
+
+        return createBinary(
+                Token.COMMA,
+                createAssignment(Token.ASSIGN, parser.createName(tempName), left),
+                hookNode);
     }
 
     private Node transformLabeledStatement(LabeledStatement ls) {
@@ -2038,27 +2067,6 @@ private static Node createBinary(int nodeType, Node left, Node right) {
                     }
                     break;
                 }
-
-            case Token.NULLISH_COALESCING:
-                {
-                    // foo ?? default =>
-                    //     (foo == undefined || foo == null) ? foo (left) : default (right)
-
-                    Node undefinedNode = new Name(0, "undefined");
-                    Node nullNode = new Node(Token.NULL);
-
-                    Node conditional =
-                            new Node(
-                                    Token.OR,
-                                    new Node(Token.SHEQ, nullNode, left),
-                                    new Node(Token.SHEQ, undefinedNode, left));
-
-                    return new Node(
-                            Token.HOOK,
-                            /* left= */ conditional,
-                            /* mid= */ right,
-                            /* right= */ left);
-                }
         }
 
         return new Node(nodeType, left, right);
diff --git a/tests/src/test/java/org/mozilla/javascript/tests/NullishCoalescingOpTest.java b/tests/src/test/java/org/mozilla/javascript/tests/NullishCoalescingOpTest.java
index 861a5d9364..8447f5af62 100644
--- a/tests/src/test/java/org/mozilla/javascript/tests/NullishCoalescingOpTest.java
+++ b/tests/src/test/java/org/mozilla/javascript/tests/NullishCoalescingOpTest.java
@@ -56,4 +56,23 @@ public void testNullishColascingPrecedence() {
                     return null;
                 });
     }
+
+    @Test
+    public void testNullishColascingEvalOnce() {
+        Utils.runWithAllOptimizationLevels(
+                cx -> {
+                    Scriptable scope = cx.initStandardObjects();
+                    cx.setLanguageVersion(Context.VERSION_ES6);
+
+                    String script1 =
+                            "var runce = 0; \n"
+                                    + "function f() { runce++; return 3; } \n"
+                                    + "var eval1 = f() ?? 42; \n"
+                                    + "runce";
+                    Assert.assertEquals(
+                            1,
+                            cx.evaluateString(scope, script1, "nullish coalescing basic", 0, null));
+                    return null;
+                });
+    }
 }