Missing properties are not enumerable when checking enumerability

When checking property enumerability _(`Object.prototype.propertyIsEnumerable`)_, missing properties should return `false` instead of throwing a `Property {0} not found.` exception. Fixes mozilla#415
whitlockjc · Apr 5, 2018 · 6e2b67f · 6e2b67f
1 parent 1a83fd3
commit 6e2b67f
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Showing 2 changed files with 46 additions and 13 deletions.
diff --git a/src/org/mozilla/javascript/NativeObject.java b/src/org/mozilla/javascript/NativeObject.java
@@ -6,6 +6,8 @@
 
 package org.mozilla.javascript;
 
+import sun.font.ScriptRun;
+
 import java.util.*;
 
 /**
@@ -181,20 +183,31 @@ public Object execIdCall(IdFunctionObject f, Context cx, Scriptable scope,
                 }
             } else {
                 String s = ScriptRuntime.toStringIdOrIndex(cx, arg);
-                if (s == null) {
-                    int index = ScriptRuntime.lastIndexResult(cx);
-                    result = thisObj.has(index, thisObj);
-                    if (result && thisObj instanceof ScriptableObject) {
-                        ScriptableObject so = (ScriptableObject) thisObj;
-                        int attrs = so.getAttributes(index);
-                        result = ((attrs & ScriptableObject.DONTENUM) == 0);
+                // When checking if a property is enumerable, a missing property should return "false" instead of
+                // throwing an exception.  See: https://github.com/mozilla/rhino/issues/415
+                try {
+                    if (s == null) {
+                        int index = ScriptRuntime.lastIndexResult(cx);
+                        result = thisObj.has(index, thisObj);
+                        s = Integer.toString(index);
+                        if (result && thisObj instanceof ScriptableObject) {
+                            ScriptableObject so = (ScriptableObject) thisObj;
+                            int attrs = so.getAttributes(index);
+                            result = ((attrs & ScriptableObject.DONTENUM) == 0);
+                        }
+                    } else {
+                        result = thisObj.has(s, thisObj);
+                        if (result && thisObj instanceof ScriptableObject) {
+                            ScriptableObject so = (ScriptableObject) thisObj;
+                            int attrs = so.getAttributes(s);
+                            result = ((attrs & ScriptableObject.DONTENUM) == 0);
+                        }
                     }
-                } else {
-                    result = thisObj.has(s, thisObj);
-                    if (result && thisObj instanceof ScriptableObject) {
-                        ScriptableObject so = (ScriptableObject) thisObj;
-                        int attrs = so.getAttributes(s);
-                        result = ((attrs & ScriptableObject.DONTENUM) == 0);
+                } catch (EvaluatorException ee) {
+                    if (ee.getMessage().startsWith(ScriptRuntime.getMessage1("msg.prop.not.found", s))) {
+                        result = false;
+                    } else {
+                        throw ee;
                     }
                 }
             }

diff --git a/testsrc/org/mozilla/javascript/tests/es5/StringPropertyIsEnumerableTest.java b/testsrc/org/mozilla/javascript/tests/es5/StringPropertyIsEnumerableTest.java
@@ -0,0 +1,20 @@
+package org.mozilla.javascript.tests.es5;
+
+import org.junit.Test;
+import org.mozilla.javascript.NativeObject;
+
+import static org.junit.Assert.assertFalse;
+import static org.mozilla.javascript.tests.Evaluator.eval;
+
+public class StringPropertyIsEnumerableTest {
+
+  @Test
+  public void testStringPropertyIsEnumerable() {
+    NativeObject object = new NativeObject();
+
+    Object result = eval("'s'.propertyIsEnumerable(0)", "obj", object);
+
+    assertFalse((Boolean)result);
+  }
+
+}