Merge pull request #3280 from AgentME/dupkeys

Fix T2462, compile duplicate keys in objects to valid strict ES5

packages/babel-plugin-transform-es2015-duplicate-keys/.npmignore

@@ -0,0 +1,3 @@
+node_modules
+src
+test

packages/babel-plugin-transform-es2015-duplicate-keys/README.md

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+# babel-plugin-transform-es2015-duplicate-keys
+
+Compile objects with duplicate keys to valid strict ES5.
+
+This plugin actually converts duplicate keys in objects to be computed
+properties, which then must be handled by the
+transform-es2015-computed-properties plugin. The final result won't contain any
+object literals with duplicate keys.
+
+## Installation
+
+```sh
+$ npm install babel-plugin-transform-es2015-duplicate-keys
+```
+
+## Usage
+
+### Via `.babelrc` (Recommended)
+
+**.babelrc**
+
+```json
+{
+  "plugins": ["transform-es2015-duplicate-keys"]
+}
+```
+
+### Via CLI
+
+```sh
+$ babel --plugins transform-es2015-duplicate-keys script.js
+```
+
+### Via Node API
+
+```javascript
+require("babel-core").transform("code", {
+  plugins: ["transform-es2015-duplicate-keys"]
+});
+```

packages/babel-plugin-transform-es2015-duplicate-keys/package.json

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+{
+  "name": "babel-plugin-transform-es2015-duplicate-keys",
+  "version": "6.4.0",
+  "description": "Compile objects with duplicate keys to valid strict ES5",
+  "repository": "https://github.com/babel/babel/tree/master/packages/babel-plugin-transform-es2015-duplicate-keys",
+  "license": "MIT",
+  "main": "lib/index.js",
+  "keywords": [
+    "babel-plugin"
+  ],
+  "dependencies": {
+    "babel-runtime": "^5.0.0",
+    "babel-types": "^6.4.0"
+  },
+  "devDependencies": {
+    "babel-helper-plugin-test-runner": "^6.3.13"
+  }
+}

packages/babel-plugin-transform-es2015-duplicate-keys/src/index.js

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+import * as t from "babel-types";
+
+function getName(key) {
+  if (t.isIdentifier(key)) {
+    return key.name;
+  }
+  return key.value.toString();
+}
+
+export default function() {
+  return {
+    visitor: {
+      ObjectExpression(path) {
+        const { node } = path;
+        const plainProps = node.properties.filter((prop) => !t.isSpreadProperty(prop) && !prop.computed);
+
+        const alreadySeenNames = Object.create(null);
+
+        for (let prop of plainProps) {
+          const name = getName(prop.key);
+          if (!alreadySeenNames[name]) {
+            alreadySeenNames[name] = true;
+          } else {
+            // Rely on the computed properties transform to split the property
+            // assignment out of the object literal.
+            prop.computed = true;
+            prop.key = t.stringLiteral(name);
+          }
+        }
+      }
+    }
+  };
+}

packages/babel-plugin-transform-es2015-duplicate-keys/test/fixtures/combination/dupes/actual.js

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+var x = { a: 5, a: 6 };

packages/babel-plugin-transform-es2015-duplicate-keys/test/fixtures/combination/dupes/expected.js

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+var x = babelHelpers.defineProperty({ a: 5 }, "a", 6);

packages/babel-plugin-transform-es2015-duplicate-keys/test/fixtures/combination/no-dupes/actual.js

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+var x = { a: 5, b: 6 };

packages/babel-plugin-transform-es2015-duplicate-keys/test/fixtures/combination/no-dupes/expected.js

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+var x = { a: 5, b: 6 };

packages/babel-plugin-transform-es2015-duplicate-keys/test/fixtures/combination/options.json

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+{
+  "plugins": ["external-helpers", "transform-es2015-duplicate-keys", "transform-es2015-computed-properties"]
+}

packages/babel-plugin-transform-es2015-duplicate-keys/test/fixtures/duplicate-keys/both-quoted/actual.js

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+var x = { "a\n b": 5, "a\n b": 6 };

packages/babel-plugin-transform-es2015-duplicate-keys/test/fixtures/duplicate-keys/both-quoted/expected.js

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+var x = { "a\n b": 5, ["a\n b"]: 6 };

packages/babel-plugin-transform-es2015-duplicate-keys/test/fixtures/duplicate-keys/dupes/actual.js

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+var x = { a: 5, a: 6 };

packages/babel-plugin-transform-es2015-duplicate-keys/test/fixtures/duplicate-keys/dupes/expected.js

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+var x = { a: 5, ["a"]: 6 };

packages/babel-plugin-transform-es2015-duplicate-keys/test/fixtures/duplicate-keys/getter/actual.js

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+var x = { a: 5, get a() {return 6;} };

packages/babel-plugin-transform-es2015-duplicate-keys/test/fixtures/duplicate-keys/getter/expected.js

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+var x = { a: 5, get ["a"]() {
+    return 6;
+  } };

packages/babel-plugin-transform-es2015-duplicate-keys/test/fixtures/duplicate-keys/no-dupes/actual.js

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+var x = { a: 5, b: 6 };

packages/babel-plugin-transform-es2015-duplicate-keys/test/fixtures/duplicate-keys/no-dupes/expected.js

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+var x = { a: 5, b: 6 };

packages/babel-plugin-transform-es2015-duplicate-keys/test/fixtures/duplicate-keys/one-quoted/actual.js

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+var x = { a: 5, "a": 6 };

packages/babel-plugin-transform-es2015-duplicate-keys/test/fixtures/duplicate-keys/one-quoted/expected.js

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+var x = { a: 5, ["a"]: 6 };

packages/babel-plugin-transform-es2015-duplicate-keys/test/fixtures/duplicate-keys/options.json

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+{
+  "plugins": ["transform-es2015-duplicate-keys"]
+}

packages/babel-plugin-transform-es2015-duplicate-keys/test/index.js

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+require("babel-helper-plugin-test-runner")(__dirname);

packages/babel-preset-es2015/index.js

@@ -8,6 +8,7 @@ module.exports = {
     require("babel-plugin-transform-es2015-classes"),
     require("babel-plugin-transform-es2015-object-super"),
     require("babel-plugin-transform-es2015-shorthand-properties"),
+    require("babel-plugin-transform-es2015-duplicate-keys"),
     require("babel-plugin-transform-es2015-computed-properties"),
     require("babel-plugin-transform-es2015-for-of"),
     require("babel-plugin-transform-es2015-sticky-regex"),

packages/babel-preset-es2015/package.json

@@ -17,6 +17,7 @@
     "babel-plugin-transform-es2015-object-super": "^6.3.13",
     "babel-plugin-transform-es2015-shorthand-properties": "^6.3.13",
     "babel-plugin-transform-es2015-computed-properties": "^6.3.13",
+    "babel-plugin-transform-es2015-duplicate-keys": "^6.4.0",
     "babel-plugin-transform-es2015-for-of": "^6.3.13",
     "babel-plugin-transform-es2015-sticky-regex": "^6.3.13",
     "babel-plugin-transform-es2015-unicode-regex": "^6.3.13",