Allow duplicate __proto__ keys in patterns, simple case (#6705) (#10532)

* Allow duplicate __proto__ keys in patterns, simple case (#6705)

* Update test262 whitelist

* Rename checkDuplicatedProto's parameter and adjust type

* Store first __proto__ redefinition's position

packages/babel-parser/src/parser/expression.js

@@ -67,14 +67,13 @@ export default class ExpressionParser extends LValParser {
   +parseFunctionParams: (node: N.Function, allowModifiers?: boolean) => void;
   +takeDecorators: (node: N.HasDecorators) => void;
 
-  // Check if property name clashes with already added.
+  // Check if property __proto__ has been used more than once.
-  // Object/class getters and setters are not allowed to clash —
+  // If the expression is a destructuring assignment, then __proto__ may appear
-  // either with each other or with an init property — and in
+  // multiple times. Otherwise, __proto__ is a duplicated key.
-  // strict mode, init properties are also not allowed to be repeated.
 
-  checkPropClash(
+  checkDuplicatedProto(
     prop: N.ObjectMember | N.SpreadElement,
-    propHash: { [key: string]: boolean },
+    protoRef: { used: boolean, start?: number },
   ): void {
     if (
       prop.type === "SpreadElement" ||
@@ -91,10 +90,12 @@ export default class ExpressionParser extends LValParser {
     const name = key.type === "Identifier" ? key.name : String(key.value);
 
     if (name === "__proto__") {
-      if (propHash.proto) {
+      // Store the first redefinition's position
-        this.raise(key.start, "Redefinition of __proto__ property");
+      if (protoRef.used && !protoRef.start) {
+        protoRef.start = key.start;
       }
-      propHash.proto = true;
+
+      protoRef.used = true;
     }
   }
 
@@ -1515,7 +1516,7 @@ export default class ExpressionParser extends LValParser {
 
       const prop = this.parseObjectMember(isPattern, refShorthandDefaultPos);
       // $FlowIgnore RestElement will never be returned if !isPattern
-      if (!isPattern) this.checkPropClash(prop, propHash);
+      if (!isPattern) this.checkDuplicatedProto(prop, propHash);
 
       // $FlowIgnore
       if (prop.shorthand) {
@@ -1525,6 +1526,10 @@ export default class ExpressionParser extends LValParser {
       node.properties.push(prop);
     }
 
+    if (!this.match(tt.eq) && propHash.start !== undefined) {
+      this.raise(propHash.start, "Redefinition of __proto__ property");
+    }
+
     return this.finishNode(
       node,
       isPattern ? "ObjectPattern" : "ObjectExpression",

packages/babel-parser/src/plugins/estree.js

@@ -125,9 +125,9 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       }
     }
 
-    checkPropClash(
+    checkDuplicatedProto(
       prop: N.ObjectMember | N.SpreadElement,
-      propHash: { [key: string]: boolean },
+      protoRef: { used: boolean, start?: number },
     ): void {
       if (
         prop.type === "SpreadElement" ||
@@ -144,10 +144,12 @@ export default (superClass: Class<Parser>): Class<Parser> =>
       const name = key.type === "Identifier" ? key.name : String(key.value);
 
       if (name === "__proto__" && prop.kind === "init") {
-        if (propHash.proto) {
+        // Store the first redefinition's position
-          this.raise(key.start, "Redefinition of __proto__ property");
+        if (protoRef.used && !protoRef.start) {
+          protoRef.start = key.start;
         }
-        propHash.proto = true;
+
+        protoRef.used = true;
       }
     }
 

packages/babel-parser/test/fixtures/es2015/destructuring/duplicate-proto/input.js

@@ -0,0 +1 @@
+({ __proto__: x, __proto__: y } = {});

packages/babel-parser/test/fixtures/es2015/destructuring/duplicate-proto/output.json

@@ -0,0 +1,207 @@
+{
+  "type": "File",
+  "start": 0,
+  "end": 38,
+  "loc": {
+    "start": {
+      "line": 1,
+      "column": 0
+    },
+    "end": {
+      "line": 1,
+      "column": 38
+    }
+  },
+  "program": {
+    "type": "Program",
+    "start": 0,
+    "end": 38,
+    "loc": {
+      "start": {
+        "line": 1,
+        "column": 0
+      },
+      "end": {
+        "line": 1,
+        "column": 38
+      }
+    },
+    "sourceType": "script",
+    "interpreter": null,
+    "body": [
+      {
+        "type": "ExpressionStatement",
+        "start": 0,
+        "end": 38,
+        "loc": {
+          "start": {
+            "line": 1,
+            "column": 0
+          },
+          "end": {
+            "line": 1,
+            "column": 38
+          }
+        },
+        "expression": {
+          "type": "AssignmentExpression",
+          "start": 1,
+          "end": 36,
+          "loc": {
+            "start": {
+              "line": 1,
+              "column": 1
+            },
+            "end": {
+              "line": 1,
+              "column": 36
+            }
+          },
+          "operator": "=",
+          "left": {
+            "type": "ObjectPattern",
+            "start": 1,
+            "end": 31,
+            "loc": {
+              "start": {
+                "line": 1,
+                "column": 1
+              },
+              "end": {
+                "line": 1,
+                "column": 31
+              }
+            },
+            "properties": [
+              {
+                "type": "ObjectProperty",
+                "start": 3,
+                "end": 15,
+                "loc": {
+                  "start": {
+                    "line": 1,
+                    "column": 3
+                  },
+                  "end": {
+                    "line": 1,
+                    "column": 15
+                  }
+                },
+                "method": false,
+                "key": {
+                  "type": "Identifier",
+                  "start": 3,
+                  "end": 12,
+                  "loc": {
+                    "start": {
+                      "line": 1,
+                      "column": 3
+                    },
+                    "end": {
+                      "line": 1,
+                      "column": 12
+                    },
+                    "identifierName": "__proto__"
+                  },
+                  "name": "__proto__"
+                },
+                "computed": false,
+                "shorthand": false,
+                "value": {
+                  "type": "Identifier",
+                  "start": 14,
+                  "end": 15,
+                  "loc": {
+                    "start": {
+                      "line": 1,
+                      "column": 14
+                    },
+                    "end": {
+                      "line": 1,
+                      "column": 15
+                    },
+                    "identifierName": "x"
+                  },
+                  "name": "x"
+                }
+              },
+              {
+                "type": "ObjectProperty",
+                "start": 17,
+                "end": 29,
+                "loc": {
+                  "start": {
+                    "line": 1,
+                    "column": 17
+                  },
+                  "end": {
+                    "line": 1,
+                    "column": 29
+                  }
+                },
+                "method": false,
+                "key": {
+                  "type": "Identifier",
+                  "start": 17,
+                  "end": 26,
+                  "loc": {
+                    "start": {
+                      "line": 1,
+                      "column": 17
+                    },
+                    "end": {
+                      "line": 1,
+                      "column": 26
+                    },
+                    "identifierName": "__proto__"
+                  },
+                  "name": "__proto__"
+                },
+                "computed": false,
+                "shorthand": false,
+                "value": {
+                  "type": "Identifier",
+                  "start": 28,
+                  "end": 29,
+                  "loc": {
+                    "start": {
+                      "line": 1,
+                      "column": 28
+                    },
+                    "end": {
+                      "line": 1,
+                      "column": 29
+                    },
+                    "identifierName": "y"
+                  },
+                  "name": "y"
+                }
+              }
+            ]
+          },
+          "right": {
+            "type": "ObjectExpression",
+            "start": 34,
+            "end": 36,
+            "loc": {
+              "start": {
+                "line": 1,
+                "column": 34
+              },
+              "end": {
+                "line": 1,
+                "column": 36
+              }
+            },
+            "properties": []
+          },
+          "extra": {
+            "parenthesized": true,
+            "parenStart": 0
+          }
+        }
+      }
+    ],
+    "directives": []
+  }
+}

scripts/tests/test262/test262_whitelist.txt

@@ -1,5 +1,3 @@
-language/expressions/assignment/destructuring/obj-prop-__proto__dup.js(default)
-language/expressions/assignment/destructuring/obj-prop-__proto__dup.js(strict mode)
 language/expressions/class/elements/fields-duplicate-privatenames.js(default)
 language/expressions/class/elements/fields-duplicate-privatenames.js(strict mode)
 language/expressions/class/elements/syntax/early-errors/grammar-private-environment-on-class-heritage-chained-usage.js(default)