From 01720715fd626374e5782c5e303a70f07698f4fa Mon Sep 17 00:00:00 2001
From: Federico Brigante <bfred-it@users.noreply.github.com>
Date: Sun, 10 Jul 2016 15:36:47 +0700
Subject: [PATCH] Transform: Object() -> {}

---
 .../__tests__/type-constructors-test.js       | 80 +++++++++++++++++++
 .../package.json                              |  4 +-
 .../src/index.js                              | 47 +++++++++++
 3 files changed, 130 insertions(+), 1 deletion(-)

diff --git a/packages/babel-plugin-minify-type-constructors/__tests__/type-constructors-test.js b/packages/babel-plugin-minify-type-constructors/__tests__/type-constructors-test.js
index e2c425725..1bbd38f5a 100644
--- a/packages/babel-plugin-minify-type-constructors/__tests__/type-constructors-test.js
+++ b/packages/babel-plugin-minify-type-constructors/__tests__/type-constructors-test.js
@@ -101,6 +101,86 @@ describe("type-constructors-plugin", () => {
     expect(transform(source)).toBe(expected);
   });
 
+
+  it("should turn Object() to {}", () => {
+    const source = "var x = Object();";
+    const expected = "var x = {};";
+    expect(transform(source)).toBe(expected);
+  });
+
+  it("should turn new Object() to {}", () => {
+    const source = "var x = new Object();";
+    const expected = "var x = {};";
+    expect(transform(source)).toBe(expected);
+  });
+
+  it("should change Object(null|undefined|{}) to {}", () => {
+    const source = unpad(`
+      [
+        Object(null),
+        Object(undefined),
+        new Object(void 0),
+        Object({})
+      ]
+    `);
+    const expected = "[{}, {}, {}, {}];";
+    expect(transform(source)).toBe(expected);
+  });
+
+  it("should change Object([]) to []", () => {
+    const source = unpad(`
+      [
+        Object([]),
+        Object([1]),
+        Object([1,2]),
+        new Object([null])
+      ]
+    `);// todo: add Object(Array())
+    const expected = "[[], [1], [1, 2], [null]];";
+    expect(transform(source)).toBe(expected);
+  });
+
+  it("should change Object(localFn) to localFn", () => {
+    const source = unpad(`
+      function a() {};
+      [
+        Object(function () {}),
+        new Object(a),
+        Object(Array)
+      ]
+    `);
+    const expected = unpad(`
+      function a() {};
+      [function () {}, a, Object(Array)];
+    `);
+    expect(transform(source)).toBe(expected);
+  });
+
+  it("shouldn't change Object(value) for unrecognized values", () => {
+    const source = unpad(`
+      [
+        Object("undefined"),
+        Object(nulled),
+        Object(false)
+      ]
+    `);
+    const expected = "[Object(\"undefined\"), Object(nulled), Object(false)];";
+    expect(transform(source)).toBe(expected);
+  });
+
+  it("should change new Object(value) to Object(value) for unrecognized values", () => {
+    const source = unpad(`
+      [
+        new Object("function"),
+        new Object(Symbol),
+        new Object(Array),
+        new Object(true)
+      ]
+    `);
+    const expected = "[Object(\"function\"), Object(Symbol), Object(Array), Object(true)];";
+    expect(transform(source)).toBe(expected);
+  });
+
   it("shouldn't change referenced identifiers", () => {
     const source = unpad(`
       (function (Boolean, String, Number, Array) {
diff --git a/packages/babel-plugin-minify-type-constructors/package.json b/packages/babel-plugin-minify-type-constructors/package.json
index e25327757..85018577e 100644
--- a/packages/babel-plugin-minify-type-constructors/package.json
+++ b/packages/babel-plugin-minify-type-constructors/package.json
@@ -11,6 +11,8 @@
   "keywords": [
     "babel-plugin"
   ],
-  "dependencies": {},
+  "dependencies": {
+    "babel-helper-is-void-0": "^0.0.0"
+  },
   "devDependencies": {}
 }
diff --git a/packages/babel-plugin-minify-type-constructors/src/index.js b/packages/babel-plugin-minify-type-constructors/src/index.js
index 35b8c5ee8..177d57a4d 100644
--- a/packages/babel-plugin-minify-type-constructors/src/index.js
+++ b/packages/babel-plugin-minify-type-constructors/src/index.js
@@ -26,6 +26,43 @@ function replaceArray(t, path) {
   }
 }
 
+function replaceObject(t, path) {
+  const { node } = path;
+  if (t.isIdentifier(node.callee, { name: "Object" }) &&
+    !path.scope.getBinding("Object")) {
+
+    const isVoid0 = require("babel-helper-is-void-0")(t);
+    const arg = node.arguments[0];
+    const binding = arg && t.isIdentifier(arg) && path.scope.getBinding(arg.name);
+
+    // Object() -> {}
+    if (node.arguments.length === 0) {
+      path.replaceWith(t.objectExpression([]));
+
+    // Object([]) -> []
+    } else if (arg.type === "ArrayExpression" ||
+      t.isFunctionExpression(arg)) {
+      path.replaceWith(arg);
+
+    // Object(null) -> {}
+    } else if (isVoid0(arg) ||
+      arg.name === "undefined" ||
+      arg.type === "NullLiteral" ||
+      arg.type === "ObjectExpression" && arg.properties.length === 0) {
+      path.replaceWith(t.objectExpression([]));
+
+    // Object(localFn) -> localFn
+    } else if (binding && binding.path.isFunction()) {
+      path.replaceWith(arg);
+
+    // new Object(a) -> Object(a)
+    } else if (node.type === "NewExpression") {
+      path.replaceWith(t.callExpression(node.callee, node.arguments));
+    }
+    return true;
+  }
+}
+
 module.exports = function({ types: t }) {
   return {
     visitor: {
@@ -60,12 +97,22 @@ module.exports = function({ types: t }) {
         if (replaceArray(t, path)) {
           return;
         }
+
+        // Object() -> {}
+        if (replaceObject(t, path)) {
+          return;
+        }
       },
       NewExpression(path) {
         // Array() -> []
         if (replaceArray(t, path)) {
           return;
         }
+
+        // Object() -> {}
+        if (replaceObject(t, path)) {
+          return;
+        }
       },
     },
   };