Add new worker for code transform, optimization, and dependency extraction

Summary:This adds a new worker implementation that

- uses the existing transforms to transform code
- optionally inline `__DEV__`, `process.env.NODE_ENV`, and `Platform.OS`
- optionally eliminate branches of conditionals with constant conditions
- extracts dependencies
- optionally minifies

This will land as part of a multi-commit stack, not in isolation

Reviewed By: martinbigio

Differential Revision: D2976677

fb-gh-sync-id: 38e317f90b6948b28ef2e3fe8b66fc0b9c75aa38
shipit-source-id: 38e317f90b6948b28ef2e3fe8b66fc0b9c75aa38

packager/react-packager/src/JSTransformer/worker/__tests__/constant-folding-test.js

@@ -0,0 +1,112 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+'use strict';
+
+jest.autoMockOff();
+const babel = require('babel-core');
+const constantFolding = require('../constant-folding');
+
+function parse(code) {
+  return babel.transform(code, {code: false, babelrc: false, compact: true});
+}
+
+describe('constant expressions', () => {
+  it('can optimize conditional expressions with constant conditions', () => {
+    const code = `
+      a(
+        'production'=="production",
+        'production'!=='development',
+        false && 1 || 0 || 2,
+        true || 3,
+        'android'==='ios' ? null : {},
+        'android'==='android' ? {a:1} : {a:0},
+        'foo'==='bar' ? b : c,
+        f() ? g() : h()
+      );`;
+    expect(constantFolding('arbitrary.js', parse(code)).code)
+      .toEqual(`a(true,true,2,true,{},{a:1},c,f()?g():h());`);
+  });
+
+  it('can optimize ternary expressions with constant conditions', () => {
+    const code =
+      `var a = true ? 1 : 2;
+       var b = 'android' == 'android'
+         ? ('production' != 'production' ? 'a' : 'A')
+         : 'i';`;
+    expect(constantFolding('arbitrary.js', parse(code)).code)
+      .toEqual(`var a=1;var b='A';`);
+  });
+
+  it('can optimize logical operator expressions with constant conditions', () => {
+    const code = `
+      var a = true || 1;
+      var b = 'android' == 'android' &&
+        'production' != 'production' || null || "A";`;
+    expect(constantFolding('arbitrary.js', parse(code)).code)
+      .toEqual(`var a=true;var b="A";`);
+  });
+
+  it('can optimize logical operators with partly constant operands', () => {
+    const code = `
+      var a = "truthy" || z();
+      var b = "truthy" && z();
+      var c = null && z();
+      var d = null || z();
+      var e = !1 && z();
+    `;
+    expect(constantFolding('arbitrary.js', parse(code)).code)
+      .toEqual(`var a="truthy";var b=z();var c=null;var d=z();var e=false;`);
+  });
+
+  it('can remode an if statement with a falsy constant test', () => {
+    const code = `
+      if ('production' === 'development' || false) {
+        var a = 1;
+      }
+    `;
+    expect(constantFolding('arbitrary.js', parse(code)).code)
+      .toEqual(``);
+  });
+
+  it('can optimize if-else-branches with constant conditions', () => {
+    const code = `
+      if ('production' == 'development') {
+        var a = 1;
+        var b = a + 2;
+      } else if ('development' == 'development') {
+        var a = 3;
+        var b = a + 4;
+      } else {
+        var a = 'b';
+      }
+    `;
+    expect(constantFolding('arbitrary.js', parse(code)).code)
+      .toEqual(`{var a=3;var b=a+4;}`);
+  });
+
+  it('can optimize nested if-else constructs', () => {
+    const code = `
+      if ('ios' === "android") {
+        if (true) {
+          require('a');
+        } else {
+          require('b');
+        }
+      } else if ('android' === 'android') {
+        if (true) {
+          require('c');
+        } else {
+          require('d');
+        }
+      }
+    `;
+    expect(constantFolding('arbitrary.js', parse(code)).code)
+      .toEqual(`{{require('c');}}`);
+  });
+});

packager/react-packager/src/JSTransformer/worker/__tests__/extract-dependencies-test.js

@@ -0,0 +1,96 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+'use strict';
+
+jest.autoMockOff();
+
+const extractDependencies = require('../extract-dependencies');
+
+describe('Dependency extraction:', () => {
+  it('can extract calls to require', () => {
+    const code = `require('foo/bar');
+      var React = require("React");
+      var A = React.createClass({
+        render: function() {
+          return require (  "Component" );
+        }
+      });
+      require
+      ('more');`
+    const {dependencies, dependencyOffsets} = extractDependencies(code);
+    expect(dependencies)
+      .toEqual(['foo/bar', 'React', 'Component', 'more']);
+    expect(dependencyOffsets).toEqual([8, 46, 147, 203]);
+  });
+
+  it('does not extract require method calls', () => {
+    const code = `
+      require('a');
+      foo.require('b');
+      bar.
+      require ( 'c').require('d')require('e')`;
+
+    const {dependencies, dependencyOffsets} = extractDependencies(code);
+    expect(dependencies).toEqual(['a', 'e']);
+    expect(dependencyOffsets).toEqual([15, 97]);
+  });
+
+  it('does not extract require calls from strings', () => {
+    const code = `require('foo');
+      var React = '\\'require("React")';
+      var a = ' // require("yadda")';
+      var a = ' /* require("yadda") */';
+      var A = React.createClass({
+        render: function() {
+          return require (  "Component" );
+        }
+      });
+      " \\" require('more')";`
+
+    const {dependencies, dependencyOffsets} = extractDependencies(code);
+    expect(dependencies).toEqual(['foo', 'Component']);
+    expect(dependencyOffsets).toEqual([8, 226]);
+  });
+
+  it('does not extract require calls in comments', () => {
+    const code = `require('foo')//require("not/this")
+      /* A comment here with a require('call') that should not be extracted */require('bar')
+    // ending comment without newline require("baz")`;
+
+    const {dependencies, dependencyOffsets} = extractDependencies(code);
+    expect(dependencies).toEqual(['foo', 'bar']);
+    expect(dependencyOffsets).toEqual([8, 122]);
+  });
+
+  it('deduplicates dependencies', () => {
+    const code = `require('foo');require( "foo" );
+      require("foo");`;
+
+    const {dependencies, dependencyOffsets} = extractDependencies(code);
+    expect(dependencies).toEqual(['foo']);
+    expect(dependencyOffsets).toEqual([8, 24, 47]);
+  });
+
+  it('does not extract calls to function with names that start with "require"', () => {
+    const code = `arbitraryrequire('foo');`;
+
+    const {dependencies, dependencyOffsets} = extractDependencies(code);
+    expect(dependencies).toEqual([]);
+    expect(dependencyOffsets).toEqual([]);
+  });
+
+  it('does not get confused by previous states', () => {
+    // yes, this was a bug
+    const code = `require("a");/* a comment */ var a = /[a]/.test('a');`
+
+    const {dependencies, dependencyOffsets} = extractDependencies(code);
+    expect(dependencies).toEqual(['a']);
+    expect(dependencyOffsets).toEqual([8]);
+  });
+});

packager/react-packager/src/JSTransformer/worker/__tests__/inline-test.js

@@ -0,0 +1,133 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+'use strict';
+
+jest.autoMockOff();
+const inline = require('../inline');
+const {transform, transformFromAst} = require('babel-core');
+
+const babelOptions = {
+  babelrc: false,
+  compact: true,
+};
+
+function toString(ast) {
+  return normalize(transformFromAst(ast, babelOptions).code);
+}
+
+function normalize(code) {
+  return transform(code, babelOptions).code;
+}
+
+function toAst(code) {
+  return transform(code, {...babelOptions, code: false}).ast;
+}
+
+describe('inline constants', () => {
+  it('replaces __DEV__ in the code', () => {
+    const code = `function a() {
+      var a = __DEV__ ? 1 : 2;
+      var b = a.__DEV__;
+      var c = function __DEV__(__DEV__) {};
+    }`
+    const {ast} = inline('arbitrary.js', {code}, {dev: true});
+    expect(toString(ast)).toEqual(normalize(code.replace(/__DEV__/, 'true')));
+  });
+
+  it('replaces Platform.OS in the code if Platform is a global', () => {
+    const code = `function a() {
+      var a = Platform.OS;
+      var b = a.Platform.OS;
+    }`
+    const {ast} = inline('arbitrary.js', {code}, {platform: 'ios'});
+    expect(toString(ast)).toEqual(normalize(code.replace(/Platform\.OS/, '"ios"')));
+  });
+
+  it('replaces Platform.OS in the code if Platform is a top level import', () => {
+    const code = `
+      var Platform = require('Platform');
+      function a() {
+        if (Platform.OS === 'android') a = function() {};
+        var b = a.Platform.OS;
+      }`
+    const {ast} = inline('arbitrary.js', {code}, {platform: 'ios'});
+    expect(toString(ast)).toEqual(normalize(code.replace(/Platform\.OS/, '"ios"')));
+  });
+
+  it('replaces require("Platform").OS in the code', () => {
+    const code = `function a() {
+      var a = require('Platform').OS;
+      var b = a.require('Platform').OS;
+    }`
+    const {ast} = inline('arbitrary.js', {code}, {platform: 'android'});
+    expect(toString(ast)).toEqual(
+      normalize(code.replace(/require\('Platform'\)\.OS/, '"android"')));
+  });
+
+  it('replaces React.Platform.OS in the code if React is a global', () => {
+    const code = `function a() {
+      var a = React.Platform.OS;
+      var b = a.React.Platform.OS;
+    }`
+    const {ast} = inline('arbitrary.js', {code}, {platform: 'ios'});
+    expect(toString(ast)).toEqual(normalize(code.replace(/React\.Platform\.OS/, '"ios"')));
+  });
+
+  it('replaces React.Platform.OS in the code if React is a top level import', () => {
+    const code = `
+      var React = require('React');
+      function a() {
+        if (React.Platform.OS === 'android') a = function() {};
+        var b = a.React.Platform.OS;
+      }`
+    const {ast} = inline('arbitrary.js', {code}, {platform: 'ios'});
+    expect(toString(ast)).toEqual(normalize(code.replace(/React.Platform\.OS/, '"ios"')));
+  });
+
+  it('replaces require("React").Platform.OS in the code', () => {
+    const code = `function a() {
+      var a = require('React').Platform.OS;
+      var b = a.require('React').Platform.OS;
+    }`
+    const {ast} = inline('arbitrary.js', {code}, {platform: 'android'});
+    expect(toString(ast)).toEqual(
+      normalize(code.replace(/require\('React'\)\.Platform\.OS/, '"android"')));
+  });
+
+  it('replaces process.env.NODE_ENV in the code', () => {
+    const code = `function a() {
+      if (process.env.NODE_ENV === 'production') {
+        return require('Prod');
+      }
+      return require('Dev');
+    }`
+    const {ast} = inline('arbitrary.js', {code}, {dev: false});
+    expect(toString(ast)).toEqual(
+      normalize(code.replace(/process\.env\.NODE_ENV/, '"production"')));
+  });
+
+  it('replaces process.env.NODE_ENV in the code', () => {
+    const code = `function a() {
+      if (process.env.NODE_ENV === 'production') {
+        return require('Prod');
+      }
+      return require('Dev');
+    }`
+    const {ast} = inline('arbitrary.js', {code}, {dev: true});
+    expect(toString(ast)).toEqual(
+      normalize(code.replace(/process\.env\.NODE_ENV/, '"development"')));
+  });
+
+  it('accepts an AST as input', function() {
+    const code = `function ifDev(a,b){return __DEV__?a:b;}`;
+    const {ast} = inline('arbitrary.hs', {ast: toAst(code)}, {dev: false});
+    expect(toString(ast)).toEqual(code.replace(/__DEV__/, 'false'))
+  });
+});
+

packager/react-packager/src/JSTransformer/worker/__tests__/minify-test.js

@@ -0,0 +1,111 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+'use strict';
+
+jest.autoMockOff();
+
+const uglify = {
+  minify: jest.genMockFunction().mockImplementation(code => {
+    return {
+      code: code.replace(/(^|\W)\s+/g, '$1'),
+      map: {},
+    };
+  }),
+};
+jest.setMock('uglify-js', uglify);
+
+const minify = require('../minify');
+const {any} = jasmine;
+
+describe('Minification:', () => {
+  const fileName = '/arbitrary/file.js';
+  const DEPENDENCY_MARKER = '\u0002\ueffe\ue277\uead5';
+  let map;
+
+  beforeEach(() => {
+    uglify.minify.mockClear();
+    map = {version: 3, sources: [fileName], mappings: ''};
+  });
+
+  it('passes the transformed code to `uglify.minify`, wrapped in an immediately invoked function expression', () => {
+    const code = 'arbitrary(code)';
+    minify('', code, {}, [], []);
+    expect(uglify.minify).toBeCalledWith(
+      `(function(){${code}}());`, any(Object));
+  });
+
+  it('uses the passed module locals as parameters of the IIFE', () => {
+    const moduleLocals = ['arbitrary', 'parameters'];
+    minify('', '', {}, [], moduleLocals);
+    expect(uglify.minify).toBeCalledWith(
+      `(function(${moduleLocals}){}());`, any(Object));
+  });
+
+  it('passes the transformed source map to `uglify.minify`', () => {
+    minify('', '', map, [], []);
+    const [, options] = uglify.minify.mock.calls[0];
+    expect(options.inSourceMap).toEqual(map);
+  });
+
+  it('passes the file name as `outSourceMap` to `uglify.minify` (uglify uses it for the `file` field on the source map)', () => {
+    minify(fileName, '', {}, [], []);
+    const [, options] = uglify.minify.mock.calls[0];
+    expect(options.outSourceMap).toEqual(fileName);
+  });
+
+  it('inserts a marker for every dependency offset before minifing', () => {
+    const code = `
+      var React = require('React');
+      var Immutable = require('Immutable');`;
+    const dependencyOffsets = [27, 67];
+    const expectedCode =
+      code.replace(/require\('/g, '$&' + DEPENDENCY_MARKER);
+
+    minify('', code, {}, dependencyOffsets, []);
+    expect(uglify.minify).toBeCalledWith(
+      `(function(){${expectedCode}}());`, any(Object));
+  });
+
+  it('returns the code provided by uglify', () => {
+    const code = 'some(source) + code';
+    uglify.minify.mockReturnValue({code: `!function(a,b,c){${code}}()`});
+
+    const result = minify('', '', {}, [], []);
+    expect(result.code).toBe(code);
+  });
+
+  it('extracts dependency offsets from the code provided by uglify', () => {
+    const code = `
+      var a=r("${DEPENDENCY_MARKER}a-dependency");
+      var b=r("\\x02\\ueffe\\ue277\\uead5b-dependency");
+      var e=r(a()?'\\u0002\\ueffe\\ue277\\uead5c-dependency'
+                 :'\x02\ueffe\ue277\uead5d-dependency');`;
+    uglify.minify.mockReturnValue({code: `!function(){${code}}());`});
+
+    const result = minify('', '', {}, [], []);
+    expect(result.dependencyOffsets).toEqual([15, 46, 81, 114]);
+  });
+
+  it('returns the source map object provided by uglify', () => {
+    uglify.minify.mockReturnValue({map, code: ''});
+    const result = minify('', '', {}, [], []);
+    expect(result.map).toBe(map);
+  });
+
+  it('adds a `moduleLocals` object to the result that reflects the names of the minified module locals', () => {
+    const moduleLocals = ['arbitrary', 'parameters', 'here'];
+    uglify.minify.mockReturnValue({code: '(function(a,ll,d){}());'});
+    const result = minify('', '', {}, [], moduleLocals);
+    expect(result.moduleLocals).toEqual({
+      arbitrary: 'a',
+      parameters: 'll',
+      here: 'd',
+    });
+  });
+});

packager/react-packager/src/JSTransformer/worker/__tests__/worker-test.js

@@ -0,0 +1,244 @@
+/**
+ * Copyright (c) 2015-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+'use strict';
+
+jest.autoMockOff();
+jest.mock('../constant-folding');
+jest.mock('../extract-dependencies');
+jest.mock('../inline');
+jest.mock('../minify');
+
+const {transformCode} = require('..');
+const {any, objectContaining} = jasmine;
+
+describe('code transformation worker:', () => {
+  let extractDependencies, transform;
+  beforeEach(() => {
+    extractDependencies =
+      require('../extract-dependencies').mockReturnValue({});
+    transform = jest.genMockFunction();
+  });
+
+  it('calls the transform with file name, source code, and transform options', function() {
+    const filename = 'arbitrary/file.js';
+    const sourceCode = 'arbitrary(code)';
+    const transformOptions = {arbitrary: 'options'};
+    transformCode(transform, filename, sourceCode, {transform: transformOptions});
+    expect(transform).toBeCalledWith(
+      {filename, sourceCode, options: transformOptions}, any(Function));
+  });
+
+  it('prefixes JSON files with an assignment to module.exports to make the code valid', function() {
+    const filename = 'arbitrary/file.json';
+    const sourceCode = '{"arbitrary":"property"}';
+    transformCode(transform, filename, sourceCode, {});
+    expect(transform).toBeCalledWith(
+      {filename, sourceCode: `module.exports=${sourceCode}`}, any(Function));
+  });
+
+  it('calls back with the result of the transform', done => {
+    const result = {
+      code: 'some.other(code)',
+      map: {}
+    };
+    transform.mockImplementation((_, callback) =>
+      callback(null, result));
+
+    transformCode(transform, 'filename', 'code', {}, (_, data) => {
+      expect(data).toEqual(objectContaining(result));
+      done();
+    });
+  });
+
+  it('removes the leading assignment to `module.exports` before passing on the result if the file is a JSON file, even if minified', done => {
+    const result = {
+      code: 'p.exports={a:1,b:2}',
+    };
+    transform.mockImplementation((_, callback) =>
+      callback(null, result));
+
+    transformCode(transform, 'aribtrary/file.json', 'b', {}, (_, data) => {
+      expect(data.code).toBe('{a:1,b:2}');
+      done();
+    });
+  });
+
+  it('calls back with any error yielded by the transform', done => {
+    const error = Error('arbitrary error');
+    transform.mockImplementation((_, callback) => callback(error));
+    transformCode(transform, 'filename', 'code', {}, e => {
+      expect(e).toBe(error);
+      done();
+    });
+  });
+
+  it('puts an empty `moduleLocals` object on the result', done => {
+    transform.mockImplementation(
+      (_, callback) => callback(null, {code: 'arbitrary'}));
+    transformCode(transform, 'filename', 'code', {}, (_, data) => {
+      expect(data.moduleLocals).toEqual({});
+      done();
+    });
+  });
+
+  it('if a `moduleLocals` array is passed, the `moduleLocals` object is a key mirror of its items', done => {
+    transform.mockImplementation(
+      (_, callback) => callback(null, {code: 'arbitrary'}));
+    const moduleLocals =
+      ['arbitrary', 'list', 'containing', 'variable', 'names'];
+
+    transformCode(transform, 'filename', 'code', {moduleLocals}, (_, data) => {
+      expect(data.moduleLocals).toEqual({
+        arbitrary: 'arbitrary',
+        list: 'list',
+        containing: 'containing',
+        variable: 'variable',
+        names: 'names',
+      });
+      done();
+    });
+  });
+
+  describe('dependency extraction:', () => {
+    let code;
+
+    beforeEach(() => {
+      transform.mockImplementation(
+        (_, callback) => callback(null, {code}));
+    });
+
+    it('passes the transformed code the `extractDependencies`', done => {
+      code = 'arbitrary(code)';
+
+      transformCode(transform, 'filename', 'code', {}, (_, data) => {
+        expect(extractDependencies).toBeCalledWith(code);
+        done();
+      });
+    });
+
+    it('uses `dependencies` and `dependencyOffsets` provided by `extractDependencies` for the result', done => {
+      const dependencyData = {
+        dependencies: ['arbitrary', 'list', 'of', 'dependencies'],
+        dependencyOffsets: [12,  119, 185, 328, 471],
+      };
+      extractDependencies.mockReturnValue(dependencyData);
+
+      transformCode(transform, 'filename', 'code', {}, (_, data) => {
+        expect(data).toEqual(objectContaining(dependencyData));
+        done();
+      });
+    });
+
+    it('does not extract requires if files are marked as "extern"', done => {
+      transformCode(transform, 'filename', 'code', {extern: true}, (_, {dependencies, dependencyOffsets}) => {
+        expect(extractDependencies).not.toBeCalled();
+        expect(dependencies).toEqual([]);
+        expect(dependencyOffsets).toEqual([]);
+        done();
+      });
+    });
+
+    it('does not extract requires of JSON files', done => {
+      transformCode(transform, 'arbitrary.json', '{"arbitrary":"json"}', {}, (_, {dependencies, dependencyOffsets}) => {
+        expect(extractDependencies).not.toBeCalled();
+        expect(dependencies).toEqual([]);
+        expect(dependencyOffsets).toEqual([]);
+        done();
+      });
+    });
+  });
+
+  describe('Minifications:', () => {
+    let constantFolding, extractDependencies, inline, minify, options;
+    let transformResult, dependencyData, moduleLocals;
+    const filename = 'arbitrary/file.js';
+    const foldedCode = 'arbitrary(folded(code));'
+    const foldedMap = {version: 3, sources: ['fold.js']}
+
+    beforeEach(() => {
+      constantFolding = require('../constant-folding')
+        .mockReturnValue({code: foldedCode, map: foldedMap});
+      extractDependencies = require('../extract-dependencies');
+      inline = require('../inline');
+      minify = require('../minify').mockReturnValue({});
+
+      moduleLocals = ['module', 'require', 'exports'];
+      options = {moduleLocals, minify: true};
+      dependencyData = {
+        dependencies: ['a', 'b', 'c'],
+        dependencyOffsets: [100, 120, 140]
+      };
+
+      extractDependencies.mockImplementation(
+        code => code === foldedCode ? dependencyData : {});
+
+      transform.mockImplementation(
+        (_, callback) => callback(null, transformResult));
+    });
+
+    it('passes the transform result to `inline` for constant inlining', done => {
+      transformResult = {map: {version: 3}, code: 'arbitrary(code)'};
+      transformCode(transform, filename, 'code', options, () => {
+        expect(inline).toBeCalledWith(filename, transformResult, options);
+        done();
+      });
+    });
+
+    it('passes the result obtained from `inline` on to `constant-folding`', done => {
+      const inlineResult = {map: {version: 3, sources: []}, ast: {}};
+      inline.mockReturnValue(inlineResult);
+      transformCode(transform, filename, 'code', options, () => {
+        expect(constantFolding).toBeCalledWith(filename, inlineResult);
+        done();
+      });
+    });
+
+    it('Uses the code obtained from `constant-folding` to extract dependencies', done => {
+      transformCode(transform, filename, 'code', options, () => {
+        expect(extractDependencies).toBeCalledWith(foldedCode);
+        done();
+      });
+    });
+
+    it('passes the code obtained from `constant-folding` to `minify`', done => {
+      transformCode(transform, filename, 'code', options, () => {
+        expect(minify).toBeCalledWith(
+          filename,
+          foldedCode,
+          foldedMap,
+          dependencyData.dependencyOffsets,
+          moduleLocals
+        );
+        done();
+      });
+    });
+
+    it('uses the dependencies obtained from the optimized result', done => {
+      transformCode(transform, filename, 'code', options, (_, result) => {
+        expect(result.dependencies).toEqual(dependencyData.dependencies);
+        done();
+      });
+    });
+
+    it('uses data produced by `minify` for the result', done => {
+      const minifyResult = {
+        code: 'minified(code)',
+        dependencyOffsets: [10, 30, 60],
+        map: {version: 3, sources: ['minified.js']},
+        moduleLocals: {module: 'x', require: 'y', exports: 'z'},
+      };
+      minify.mockReturnValue(minifyResult);
+
+      transformCode(transform, 'filename', 'code', options, (_, result) => {
+        expect(result).toEqual(objectContaining(minifyResult))
+        done();
+      });
+    });
+  });
+});

packager/react-packager/src/JSTransformer/worker/constant-folding.js

@@ -0,0 +1,82 @@
+/**
+ * Copyright (c) 2016-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+'use strict';
+
+const babel = require('babel-core');
+const t = babel.types;
+
+const isLiteral = binaryExpression =>
+  t.isLiteral(binaryExpression.left) && t.isLiteral(binaryExpression.right);
+
+const Conditional = {
+  exit(path) {
+    const node = path.node;
+    const test = node.test;
+    if (t.isLiteral(test)) {
+      if (test.value || node.alternate) {
+        path.replaceWith(test.value ? node.consequent : node.alternate);
+      } else if (!test.value) {
+        path.remove();
+      }
+    }
+  },
+};
+
+const plugin = {
+  visitor: {
+    BinaryExpression: {
+      exit(path) {
+        const node = path.node;
+        if (t.isLiteral(node.left) && t.isLiteral(node.right)) {
+          const result = path.evaluate();
+          if (result.confident) {
+            path.replaceWith(t.valueToNode(result.value));
+          }
+        }
+      },
+    },
+    ConditionalExpression: Conditional,
+    IfStatement: Conditional,
+    LogicalExpression: {
+      exit(path) {
+        const node = path.node;
+        const left = node.left;
+        if (t.isLiteral(left)) {
+          const value = t.isNullLiteral(left) ? null : left.value;
+          if (node.operator === '||') {
+            path.replaceWith(value ? left : node.right);
+          } else {
+            path.replaceWith(value ? node.right : left);
+          }
+        }
+      }
+    },
+    UnaryExpression: {
+      exit(path) {
+        const node = path.node;
+        if (node.operator === '!' && t.isLiteral(node.argument)) {
+          path.replaceWith(t.valueToNode(!node.argument.value));
+        }
+      }
+    },
+  },
+};
+
+function constantFolding(filename, transformResult) {
+  return babel.transformFromAst(transformResult.ast, transformResult.code, {
+    filename,
+    plugins: [plugin],
+    inputSourceMap: transformResult.map,
+    babelrc: false,
+    compact: true,
+  })
+}
+
+module.exports = constantFolding;
+

packager/react-packager/src/JSTransformer/worker/extract-dependencies.js

@@ -0,0 +1,126 @@
+/**
+ * Copyright (c) 2016-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+'use strict';
+
+const SINGLE_QUOTE = "'".charCodeAt(0);
+const DOUBLE_QUOTE = '"'.charCodeAt(0);
+const BACKSLASH = '\\'.charCodeAt(0);
+const SLASH = '/'.charCodeAt(0);
+const NEWLINE = '\n'.charCodeAt(0);
+const ASTERISK = '*'.charCodeAt(0);
+
+// dollar is the only regex special character valid in identifiers
+const escapeRegExp = identifier => identifier.replace(/[$]/g, '\\$');
+
+function binarySearch(indexes, index) {
+  var low = 0;
+  var high = indexes.length - 1;
+  var i = 0;
+
+  if (indexes[low] === index) {
+    return low;
+  }
+  while (high - low > 1) {
+    var current = low + ((high - low) >>> 1); // right shift divides by 2 and floors
+    if (index === indexes[current]) {
+      return current;
+    }
+    if (index > indexes[current]) {
+      low = current;
+    } else {
+      high = current;
+    }
+  }
+  return low;
+}
+
+function indexOfCharCode(string, needle, i) {
+  for (var charCode; (charCode = string.charCodeAt(i)); i++) {
+    if (charCode === needle) {
+      return i;
+    }
+  }
+  return -1;
+}
+
+const reRequire = /(?:^|[^.\s])\s*\brequire\s*\(\s*(['"])(.*?)\1/g;
+
+/**
+ * Extracts dependencies (module IDs imported with the `require` function) from
+ * a string containing code.
+ * The function is regular expression based for speed reasons.
+ *
+ * The code is traversed twice:
+ *  1. An array of ranges is built, where indexes 0-1, 2-3, 4-5, etc. are code,
+ *     and indexes 1-2, 3-4, 5-6, etc. are string literals and comments.
+ *  2. require calls are extracted with a regular expression.
+ *
+ * The result of the dependency extraction is an de-duplicated array of
+ * dependencies, and an array of offsets to the string literals with module IDs.
+ * The index points to the opening quote.
+ */
+function extractDependencies(code) {
+  const ranges = [0];
+  // are we currently in a quoted string? -> SINGLE_QUOTE or DOUBLE_QUOTE, else undefined
+  var currentQuote;
+  // scan the code for string literals and comments.
+  for (var i = 0, charCode; (charCode = code.charCodeAt(i)); i++) {
+    if (charCode === BACKSLASH) {
+      i += 1;
+      continue;
+    }
+
+    if (charCode === SLASH && currentQuote === undefined) {
+      var next = code.charCodeAt(i + 1);
+      var end = undefined;
+      if (next === SLASH) {
+        end = indexOfCharCode(code, NEWLINE, i + 2);
+      } else if (next === ASTERISK) {
+        end = code.indexOf('*/', i + 2) + 1; // assume valid JS input here
+      }
+      if (end === -1) {
+        // if the comment does not end, it goes to the end of the file
+        end += code.length;
+      }
+      if (end !== undefined) {
+        ranges.push(i, end);
+        i = end;
+        continue;
+      }
+    }
+
+    var isQuoteStart = currentQuote === undefined &&
+                       (charCode === SINGLE_QUOTE || charCode === DOUBLE_QUOTE);
+    if (isQuoteStart || currentQuote === charCode) {
+      ranges.push(i);
+      currentQuote = currentQuote === charCode ? undefined : charCode;
+    }
+  }
+  ranges.push(i);
+
+  // extract dependencies
+  const dependencies = new Set();
+  const dependencyOffsets = [];
+  for (var match; (match = reRequire.exec(code)); ) {
+    // check whether the match is in a code range, and not inside of a string
+    // literal or a comment
+    if (binarySearch(ranges, match.index) % 2 === 0) {
+      dependencies.add(match[2]);
+      dependencyOffsets.push(
+        match[0].length - match[2].length - 2 + match.index);
+    }
+  }
+
+  return {
+    dependencyOffsets,
+    dependencies: Array.from(dependencies.values()),
+  };
+}
+
+module.exports = extractDependencies;

packager/react-packager/src/JSTransformer/worker/index.js

@@ -0,0 +1,79 @@
+/**
+ * Copyright (c) 2016-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+'use strict';
+
+const constantFolding = require('./constant-folding');
+const extractDependencies = require('./extract-dependencies');
+const inline = require('./inline');
+const minify = require('./minify');
+
+function keyMirrorFromArray(array) {
+  var keyMirror = {};
+  array.forEach(key => keyMirror[key] = key);
+  return keyMirror;
+}
+
+function makeTransformParams(filename, sourceCode, options) {
+  if (filename.endsWith('.json')) {
+    sourceCode = 'module.exports=' + sourceCode;
+  }
+  return {filename, sourceCode, options};
+}
+
+function transformCode(transform, filename, sourceCode, options, callback) {
+  const params = makeTransformParams(filename, sourceCode, options.transform);
+  const moduleLocals = options.moduleLocals || [];
+  const isJson = filename.endsWith('.json');
+
+  transform(params, (error, transformed) => {
+    if (error) {
+      callback(error);
+      return;
+    }
+
+    var code, map;
+    if (options.minify) {
+      const optimized =
+        constantFolding(filename, inline(filename, transformed, options));
+      code = optimized.code;
+      map = optimized.map;
+    } else {
+      code = transformed.code;
+      map = transformed.map;
+    }
+
+    if (isJson) {
+      code = code.replace(/^\w+\.exports=/, '');
+    }
+
+    const moduleLocals = options.moduleLocals || [];
+    const dependencyData = isJson || options.extern
+      ? {dependencies: [], dependencyOffsets: []}
+      : extractDependencies(code);
+
+    var result;
+    if (options.minify) {
+      result = minify(
+        filename, code, map, dependencyData.dependencyOffsets, moduleLocals);
+      result.dependencies = dependencyData.dependencies;
+    } else {
+      result = dependencyData;
+      result.code = code;
+      result.map = map;
+      result.moduleLocals = keyMirrorFromArray(moduleLocals);
+    }
+
+    callback(null, result);
+  });
+}
+
+module.exports = function(transform, filename, sourceCode, options, callback) {
+  transformCode(require(transform), filename, sourceCode, options || {}, callback);
+};
+module.exports.transformCode = transformCode; // for easier testing

packager/react-packager/src/JSTransformer/worker/inline.js

@@ -0,0 +1,102 @@
+/**
+ * Copyright (c) 2016-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+'use strict';
+
+const babel = require('babel-core');
+const t = babel.types;
+
+const react = {name: 'React'};
+const platform = {name: 'Platform'};
+const os = {name: 'OS'};
+const requirePattern = {name: 'require'};
+
+const env = {name: 'env'};
+const nodeEnv = {name: 'NODE_ENV'};
+const processId = {name: 'process'};
+
+const dev = {name: '__DEV__'};
+
+const isGlobal = (binding) => !binding;
+
+const isToplevelBinding = (binding) => isGlobal(binding) || !binding.scope.parent;
+
+const isRequireCall = (node, dependencyId, scope) =>
+  t.isCallExpression(node) &&
+  t.isIdentifier(node.callee, requirePattern) &&
+  t.isStringLiteral(node.arguments[0], t.stringLiteral(dependencyId));
+
+const isImport = (node, scope, pattern) =>
+  t.isIdentifier(node, pattern) &&
+  isToplevelBinding(scope.getBinding(pattern.name)) ||
+  isRequireCall(node, pattern.name, scope);
+
+const isPlatformOS = (node, scope) =>
+  t.isIdentifier(node.property, os) &&
+  isImport(node.object, scope, platform);
+
+const isReactPlatformOS = (node, scope) =>
+  t.isIdentifier(node.property, os) &&
+  t.isMemberExpression(node.object) &&
+  t.isIdentifier(node.object.property, platform) &&
+  isImport(node.object.object, scope, react);
+
+const isProcessEnvNodeEnv = (node, scope) =>
+  t.isIdentifier(node.property, nodeEnv) &&
+  t.isMemberExpression(node.object) &&
+  t.isIdentifier(node.object.property, env) &&
+  t.isIdentifier(node.object.object, processId) &&
+  isGlobal(scope.getBinding(processId.name));
+
+const isDev = (node, parent, scope) =>
+  t.isIdentifier(node, dev) &&
+  isGlobal(scope.getBinding(dev.name)) &&
+  !(t.isMemberExpression(parent));
+
+const inlinePlugin = {
+  visitor: {
+    Identifier(path, state) {
+      if (isDev(path.node, path.parent, path.scope)) {
+        path.replaceWith(t.booleanLiteral(state.opts.dev));
+      }
+    },
+    MemberExpression(path, state) {
+      const node = path.node;
+      const scope = path.scope;
+
+      if (isPlatformOS(node, scope) || isReactPlatformOS(node, scope)) {
+        path.replaceWith(t.stringLiteral(state.opts.platform));
+      }
+
+      if(isProcessEnvNodeEnv(node, scope)) {
+        path.replaceWith(
+          t.stringLiteral(state.opts.dev ? 'development' : 'production'));
+      }
+    },
+  },
+};
+
+const plugin = () => inlinePlugin;
+
+function inline(filename, transformResult, options) {
+  const code = transformResult.code;
+  const babelOptions = {
+    filename,
+    plugins: [[plugin, options]],
+    inputSourceMap: transformResult.map,
+    code: false,
+    babelrc: false,
+    compact: true,
+  };
+
+  return transformResult.ast
+      ? babel.transformFromAst(transformResult.ast, code, babelOptions)
+      : babel.transform(code, babelOptions);
+}
+
+module.exports = inline;

packager/react-packager/src/JSTransformer/worker/minify.js

@@ -0,0 +1,88 @@
+/**
+ * Copyright (c) 2016-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+'use strict';
+
+const uglify = require('uglify-js');
+
+const MAGIC_MARKER = '\u0002\ueffe\ue277\uead5';
+const MAGIC_MARKER_SPLITTER =
+  /(?:\x02|\\u0002|\\x02)(?:\ueffe|\\ueffe)(?:\ue277|\\ue277)(?:\uead5|\\uead5)/;
+
+// IIFE = "immediately invoked function expression"
+// we wrap modules in functions to allow the minifier to mangle local variables
+function wrapCodeInIIFE(code, moduleLocals) {
+  return `(function(${moduleLocals.join(',')}){${code}}());`;
+}
+
+function extractCodeFromIIFE(code) {
+  return code.substring(code.indexOf('{') + 1, code.lastIndexOf('}'));
+}
+
+function extractModuleLocalsFromIIFE(code) {
+  return code.substring(code.indexOf('(', 1) + 1, code.indexOf(')')).split(',');
+}
+
+function splitFirstElementAt(array, offset) {
+  const first = array.shift();
+  array.unshift(first.slice(0, offset + 1), first.slice(offset + 1));
+  return array;
+}
+
+function insertMarkers(code, dependencyOffsets) {
+  return dependencyOffsets
+    .reduceRight(splitFirstElementAt, [code])
+    .join(MAGIC_MARKER);
+}
+
+function extractMarkers(codeWithMarkers) {
+  const dependencyOffsets = [];
+  const codeBits = codeWithMarkers.split(MAGIC_MARKER_SPLITTER);
+  var offset = 0;
+  for (var i = 0, max = codeBits.length - 1; i < max; i++) {
+    offset += codeBits[i].length;
+    dependencyOffsets.push(offset - 1);
+  }
+
+  return {code: codeBits.join(''), dependencyOffsets};
+}
+
+function minify(filename, code, map, dependencyOffsets, moduleLocals) {
+  // before minifying, code is wrapped in an immediately invoked function
+  // expression, so that top level variables can be shortened safely
+  code = wrapCodeInIIFE(
+    // since we don't know where the strings specifying dependencies will be
+    // located in the minified code, we mark them with a special marker string
+    // and extract them afterwards.
+    // That way, post-processing code can use these positions
+    insertMarkers(code, dependencyOffsets),
+    moduleLocals
+  );
+
+  const minifyResult = uglify.minify(code, {
+    fromString: true,
+    inSourceMap: map,
+    outSourceMap: filename,
+    output: {
+      ascii_only: true,
+      screw_ie8: true,
+    },
+  });
+
+  const minifiedModuleLocals = extractModuleLocalsFromIIFE(minifyResult.code);
+  const codeWithMarkers = extractCodeFromIIFE(minifyResult.code);
+  const result = extractMarkers(codeWithMarkers);
+  result.map = minifyResult.map;
+  result.moduleLocals = {};
+  moduleLocals.forEach(
+    (key, i) => result.moduleLocals[key] = minifiedModuleLocals[i]);
+
+  return result;
+}
+
+module.exports = minify;