Allow duplicate function keys

Allow duplicate function keys when a modern language version (>= ES6) is selected.

---------

Co-authored-by: vladimir.zhuravlev <[email protected]>

Author: zhurvla

rhino/src/main/java/org/mozilla/javascript/Parser.java

@@ -3908,12 +3908,10 @@ private ObjectLiteral objectLiteral() throws IOException {
 
             if (this.inUseStrictDirective
                     && propertyName != null
-                    && !(pname instanceof ComputedPropertyKey)) {
+                    && !(pname instanceof ComputedPropertyKey)
+                    && compilerEnv.getLanguageVersion() < Context.VERSION_ES6) {
                 switch (entryKind) {
                     case PROP_ENTRY:
-                        if (compilerEnv.getLanguageVersion() >= Context.VERSION_ES6) {
-                            break;
-                        }
                     case METHOD_ENTRY:
                         if (getterNames.contains(propertyName)
                                 || setterNames.contains(propertyName)) {

rhino/src/test/java/org/mozilla/javascript/tests/DuplicateProperties.java

@@ -0,0 +1,79 @@
+package org.mozilla.javascript.tests;
+
+import org.junit.Test;
+import org.mozilla.javascript.testutils.Utils;
+
+public class DuplicatePropertiesTest {
+    @Test
+    public void duplicateProperty() {
+        String script =
+                "(function() {\n"
+                        + "'use strict';\n"
+                        + "const o = {foo: 1, foo: 2};\n"
+                        + "return o.foo\n"
+                        + "})();";
+
+        Utils.assertEvaluatorException_1_8(
+                "Property \"foo\" already defined in this object literal", script);
+
+        Utils.assertWithAllModes_ES6(2, script);
+    }
+
+    @Test
+    public void duplicatePropertyFunction() {
+        String script =
+                "(function() {\n"
+                        + "'use strict';\n"
+                        + "var o = {\n"
+                        + "  foo: 1,\n"
+                        + "  foo() {return 'Hello';},\n"
+                        + "  foo: 2,\n"
+                        + "  foo() {return 'Hello2';},\n"
+                        + "};\n"
+                        + "return o.foo;\n"
+                        + "})()();";
+
+        Utils.assertEvaluatorException_1_8(
+                "Property \"foo\" already defined in this object literal", script);
+
+        Utils.assertWithAllModes_ES6("Hello2", script);
+    }
+
+    @Test
+    public void duplicatePropertyFunctionGetter() {
+        String script =
+                "(function() {\n"
+                        + "'use strict';\n"
+                        + "var o = {\n"
+                        + "  foo: 1,\n"
+                        + "  get foo() {return 'Hello2';},\n"
+                        + "  get foo() {return 'Hello2';},\n"
+                        + "};\n"
+                        + "return o.foo;\n"
+                        + "})();";
+
+        Utils.assertEvaluatorException_1_8(
+                "Property \"foo\" already defined in this object literal", script);
+
+        Utils.assertWithAllModes_ES6("Hello2", script);
+    }
+
+    @Test
+    public void duplicatePropertyFunctionSetter() {
+        String script =
+                "(function() {\n"
+                        + "'use strict';\n"
+                        + "var o = {\n"
+                        + "  foo: 1,\n"
+                        + "  set foo(val) {return val},\n"
+                        + "  set foo(val) {return val},\n"
+                        + "};\n"
+                        + "return o.foo = 'Hello2';\n"
+                        + "})();";
+
+        Utils.assertEvaluatorException_1_8(
+                "Property \"foo\" already defined in this object literal", script);
+
+        Utils.assertWithAllModes_ES6("Hello2", script);
+    }
+}

rhino/src/test/java/org/mozilla/javascript/tests/DuplicatePropertiesTest.java

@@ -4686,7 +4686,7 @@ language/expressions/new 22/59 (37.29%)
 
 ~language/expressions/new.target
 
-language/expressions/object 692/1170 (59.15%)
+language/expressions/object 688/1170 (58.8%)
     dstr/async-gen-meth-ary-init-iter-close.js {unsupported: [async-iteration, async]}
     dstr/async-gen-meth-ary-init-iter-get-err.js {unsupported: [async-iteration]}
     dstr/async-gen-meth-ary-init-iter-get-err-array-prototype.js {unsupported: [async-iteration]}
@@ -5358,10 +5358,6 @@ language/expressions/object 692/1170 (59.15%)
     prop-def-id-eval-error.js non-strict
     prop-def-id-eval-error-2.js non-strict
     prop-dup-get-data.js strict
-    prop-dup-get-get.js strict
-    prop-dup-get-set-get.js strict
-    prop-dup-set-get-set.js strict
-    prop-dup-set-set.js strict
     scope-gen-meth-body-lex-distinct.js non-strict
     scope-gen-meth-param-rest-elem-var-close.js non-strict
     scope-gen-meth-param-rest-elem-var-open.js non-strict