always coerce leading computed property initialisers into the init object - fixes #1820

src/babel/transformation/transformers/es6/properties.computed.js

@@ -1,8 +1,8 @@
 import * as t from "../../../types";
 
 function loose(node, body, objId) {
-  for (var i = 0; i < node.properties.length; i++) {
+  for (var prop of (node.properties: Array)) {
-    var prop = node.properties[i];
+    if (!prop) continue;
 
     body.push(t.expressionStatement(
       t.assignmentExpression(
@@ -15,32 +15,18 @@ function loose(node, body, objId) {
 }
 
 function spec(node, body, objId, initProps, file) {
-  var props = node.properties;
-
-  // add all non-computed properties and `__proto__` properties to the initializer
-
-  var broken = false;
-
-  for (let i = 0; i < props.length; i++) {
-    let prop = props[i];
-
-    if (prop.computed) {
-      broken = true;
-    }
-
-    if (prop.kind !== "init" || !broken || t.isLiteral(t.toComputedKey(prop, prop.key), { value: "__proto__" })) {
-      initProps.push(prop);
-      props[i] = null;
-    }
-  }
-
   // add a simple assignment for all Symbol member expressions due to symbol polyfill limitations
   // otherwise use Object.defineProperty
 
-  for (let i = 0; i < props.length; i++) {
+  for (let prop of (node.properties: Array)) {
-    let prop = props[i];
     if (!prop) continue;
 
+    // this wont work with Object.defineProperty
+    if (t.isLiteral(t.toComputedKey(prop), { value: "__proto__" })) {
+      initProps.push(prop);
+      continue;
+    }
+
     let key = prop.key;
     if (t.isIdentifier(key) && !prop.computed) {
       key = t.literal(key.name);
@@ -68,14 +54,33 @@ export var visitor = {
     exit(node, parent, scope, file) {
       var hasComputed = false;
 
-      for (var prop of (node.properties: Array)) {
+      for (let prop of (node.properties: Array)) {
         hasComputed = t.isProperty(prop, { computed: true, kind: "init" });
         if (hasComputed) break;
       }
 
       if (!hasComputed) return;
 
+      // put all getters/setters into the first object expression as well as all initialisers up
+      // to the first computed property
+
       var initProps = [];
+      var stopInits = false;
+
+      for (var i = 0; i < node.properties.length; i++) {
+        let prop = node.properties[i];
+        if (prop.computed) {
+          stopInits = true;
+        }
+
+        if (prop.kind !== "init" || !stopInits) {
+          initProps.push(prop);
+          node.properties[i] = null;
+        }
+      }
+
+      //
+
       var objId = scope.generateUidIdentifierBasedOnNode(parent);
 
       //

test.js

@@ -0,0 +1,36 @@
+var uglify = require("uglify-js");
+var babel  = require(".");
+var zlib   = require("zlib");
+var vm     = require("vm");
+var fs     = require("fs");
+
+var code = fs.readFileSync("/Users/sebmck/Downloads/jquery-1.11.3 (1).js", "utf8");
+
+function sizeof(name, fn) {
+  var start = Date.now();
+  var code = fn();
+  var end = Date.now();
+  console.log(name, "time:", (end - start) + "ms", "raw:", (code.length / 1000) + "KB", "gzipped:", (zlib.gzipSync(code).length / 1000) + "KB");
+  fs.writeFileSync("jquery." + name + ".js", code);
+  new Function(code);
+}
+
+sizeof("raw", function () {
+  return code;
+});
+
+sizeof("babel", function () {
+  return babel.transform(code, {
+    compact: true,
+    experimental: true,
+    blacklist: ["strict"],
+    plugins: ["minify-booleans", "merge-sibling-variables"]
+  }).code;
+});
+
+sizeof("uglify", function () {
+  return uglify.minify(code, {
+    mangle: false,
+    fromString: true
+  }).code;
+});

test/core/fixtures/transformation/es6.properties.computed-loose/coerce/expected.js

@@ -0,0 +1,7 @@
+"use strict";
+
+var _obj;
+
+var obj = (_obj = {
+  foo: "bar"
+}, _obj[bar] = "foo", _obj);

test/core/fixtures/transformation/es6.properties.computed-loose/options.json

@@ -1,3 +1,4 @@
 {
+  "blacklist": ["es5.properties.mutators"],
   "loose": ["es6.properties.computed"]
 }

test/core/fixtures/transformation/es6.properties.computed-loose/two/actual.js

@@ -1,4 +1,4 @@
 var obj = {
   first: "first",
-  ["second"]: "second",
+  [second]: "second",
 };

test/core/fixtures/transformation/es6.properties.computed-loose/two/expected.js

@@ -2,4 +2,6 @@
 
 var _obj;
 
-var obj = (_obj = {}, _obj.first = "first", _obj["second"] = "second", _obj);
+var obj = (_obj = {
+  first: "first"
+}, _obj[second] = "second", _obj);