Handle side effects correctly in rest params index expressions (#4348) (

#4674)
babel · Oct 5, 2016 · 0366d1a · 0366d1a
1 parent 7a7704f
commit 0366d1a
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Showing 4 changed files with 33 additions and 6 deletions.
diff --git a/packages/babel-plugin-transform-es2015-parameters/src/rest.js b/packages/babel-plugin-transform-es2015-parameters/src/rest.js
@@ -17,6 +17,10 @@ let restIndex = template(`
   ARGUMENTS.length <= INDEX ? undefined : ARGUMENTS[INDEX]
 `);
 
+let restIndexImpure = template(`
+  REF = INDEX, ARGUMENTS.length <= REF ? undefined : ARGUMENTS[REF]
+`);
+
 let restLength = template(`
   ARGUMENTS.length <= OFFSET ? 0 : ARGUMENTS.length - OFFSET
 `);
@@ -161,10 +165,21 @@ function optimiseIndexGetter(path, argsId, offset) {
     index = t.binaryExpression("+", path.parent.property, t.numericLiteral(offset));
   }
 
-  path.parentPath.replaceWith(restIndex({
-    ARGUMENTS: argsId,
-    INDEX: index,
-  }));
+  const { scope } = path;
+  if (!scope.isPure(index)) {
+    let temp = scope.generateUidIdentifierBasedOnNode(index);
+    scope.push({id: temp, kind: "var"});
+    path.parentPath.replaceWith(restIndexImpure({
+      ARGUMENTS: argsId,
+      INDEX: index,
+      REF: temp
+    }));
+  } else {
+    path.parentPath.replaceWith(restIndex({
+      ARGUMENTS: argsId,
+      INDEX: index,
+    }));
+  }
 }
 
 function optimiseLengthGetter(path, argsId, offset) {

diff --git a/...bel-plugin-transform-es2015-parameters/test/fixtures/parameters/regression-4348/actual.js b/...bel-plugin-transform-es2015-parameters/test/fixtures/parameters/regression-4348/actual.js
@@ -0,0 +1,4 @@
+function first(...values) {
+  var index = 0;
+  return values[index++];
+}
diff --git a/...l-plugin-transform-es2015-parameters/test/fixtures/parameters/regression-4348/expected.js b/...l-plugin-transform-es2015-parameters/test/fixtures/parameters/regression-4348/expected.js
@@ -0,0 +1,6 @@
+function first() {
+  var _ref;
+
+  var index = 0;
+  return _ref = index++ + 0, arguments.length <= _ref ? undefined : arguments[_ref];
+}
diff --git a/...babel-plugin-transform-es2015-parameters/test/fixtures/parameters/rest-length/expected.js b/...babel-plugin-transform-es2015-parameters/test/fixtures/parameters/rest-length/expected.js
@@ -1,6 +1,8 @@
 var t = function (f) {
+  var _ref;
+
   arguments.length <= 1 ? undefined : arguments[1];
-  arguments.length <= (arguments.length <= 1 ? 0 : arguments.length - 1) - 1 + 1 ? undefined : arguments[(arguments.length <= 1 ? 0 : arguments.length - 1) - 1 + 1];
+  _ref = (arguments.length <= 1 ? 0 : arguments.length - 1) - 1 + 1, arguments.length <= _ref ? undefined : arguments[_ref];
 };
 
 function t(f) {
@@ -11,4 +13,4 @@ function t(f) {
   items;
   items[0];
   items[items.length - 1];
-}
+}