Add CoffeeScript2 as an example repo (#130)

The CS2 compiler is a good example of CS2 code, so it's probably the most
reasonable test case. For now, this is based off of the config for CS1, but it
may need to be tweaked.

Author: alangpierce

examples/coffeescript2/.gitignore_extension

@@ -0,0 +1,2 @@
+!test/*.js
+examples-tmp

examples/coffeescript2/babelrc

@@ -0,0 +1,7 @@
+{
+  "presets": ["env"],
+  "plugins": ["transform-remove-strict-mode"],
+  "parserOpts": {
+    "allowReturnOutsideFunction": true
+  }
+}

examples/coffeescript2/bulk-decaffeinate.config.js

@@ -0,0 +1,12 @@
+module.exports = {
+  searchDirectory: '.',
+  filesToProcess: ['./Cakefile'],
+  customNames: {
+    './Cakefile': './Cakefile.js',
+  },
+  fileFilterFn: path => !path.includes('test/importing/') && !path.includes('documentation'),
+  jscodeshiftScripts: [
+    'top-level-this-to-exports.js',
+  ],
+  decaffeinateArgs: ['--use-cs2'],
+};

examples/coffeescript2/config.js

@@ -0,0 +1,20 @@
+export default {
+  cloneUrl: 'https://github.com/jashkenas/coffeescript.git',
+  forkUrl: '[email protected]:decaffeinate-examples/coffeescript2.git',
+  useDefaultConfig: true,
+  extraDependencies: [
+    'babel-plugin-transform-remove-strict-mode',
+    'js-cake',
+    'require-uncached',
+  ],
+  testCommands: [`
+    set -e
+    npm install
+    ./node_modules/.bin/babel src -d lib/coffee-script
+    git commit -a -m 'Rebuild CoffeeScript with new code'
+    ./check-coffeescript-examples.sh
+    ./node_modules/.bin/js-cake test
+  `],
+  expectConversionSuccess: true,
+  expectTestSuccess: true,
+};

examples/coffeescript2/decaffeinate.patch

@@ -0,0 +1,222 @@
+diff --git a/Cakefile.js b/Cakefile.js
+index a70d4c7..3bb3e35 100644
+--- a/Cakefile.js
++++ b/Cakefile.js
+@@ -458,6 +458,8 @@ task('bench', 'quick benchmark of compilation time', () => {
+ // Run the CoffeeScript test suite.
+ var runTests = function (CoffeeScript) {
+   CoffeeScript.register();
++  require('babel-register');
++  require('babel-polyfill');
+   const startTime = Date.now();
+   let currentFile = null;
+   let passedTests = 0;
+@@ -510,14 +512,14 @@ var runTests = function (CoffeeScript) {
+   const files = fs.readdirSync('test');
+
+   for (const file of Array.from(files)) {
+-    if (helpers.isCoffee(file)) {
++    if (file.endsWith('.js')) {
+       var filename;
+
+       const literate = helpers.isLiterate(file);
+       currentFile = (filename = path.join('test', file));
+       const code = fs.readFileSync(filename);
+       try {
+-        CoffeeScript.run(code.toString(), { filename, literate });
++        require(`./${filename}`);
+       } catch (error1) {
+         const error = error1;
+         failures.push({ filename, error });
+diff --git a/check-coffeescript-examples.sh b/check-coffeescript-examples.sh
+new file mode 100755
+index 0000000..5d768d2
+--- /dev/null
++++ b/check-coffeescript-examples.sh
+@@ -0,0 +1,20 @@
++#!/bin/bash
++
++# Simple shell script to compare the decaffeinated CoffeeScript compiler
++# with the official one, running it on all CoffeeScript files in the repo and
++# making sure the output is the same. For now, it just fails on the first error.
++
++set -e
++
++rm -rf examples-tmp
++mkdir examples-tmp
++cd examples-tmp
++git clone https://github.com/jashkenas/coffeescript.git
++
++for path in $(find coffeescript -name '*.coffee'); do
++  echo "Comparing ${path}..."
++  (./coffeescript/bin/coffee --compile --print ${path} || echo 'ERROR') > expected.js
++  (../bin/coffee --compile --print ${path} || echo 'ERROR') > actual.js
++  cmp expected.js actual.js
++  echo 'Passed!'
++done
+diff --git a/test/classes.js b/test/classes.js
+index ffff3f6..fe1bf20 100644
+--- a/test/classes.js
++++ b/test/classes.js
+@@ -146,7 +146,8 @@ test("Overriding the static property new doesn't clobber Function::new", () => {
+
+   Function.prototype.new = function () { return new (this)(...arguments); };
+
+-  ok((TwoClass.new('three')).name === 'three');
++  // https://github.com/decaffeinate/decaffeinate/blob/master/docs/correctness-issues.md#static-property-inheritance-is-implemented-differently
++  // ok((TwoClass.new('three')).name === 'three');
+   ok((new OneClass()).function === 'function');
+   ok(OneClass.new === 'new');
+
+@@ -610,7 +611,8 @@ test('variables in constructor bodies are correctly scoped', () => {
+
+   const a = new A();
+   eq(a.captured().x, 10);
+-  return eq(a.captured().y, 2);
++  // https://github.com/decaffeinate/decaffeinate/blob/master/docs/correctness-issues.md#executable-class-bodies-can-have-their-statements-reordered
++  return eq(a.captured().y, 20);
+ });
+
+
+@@ -671,7 +673,8 @@ test('ensure that constructors invoked with splats return a new object', () => {
+   // Ensure that constructors invoked with splats cache the function.
+   let called = 0;
+   const get = function () { if (called++) { return false; } return (Type = class Type {}); };
+-  return new get()(...Array.from(args || []));
++  // https://github.com/decaffeinate/decaffeinate/blob/master/docs/correctness-issues.md#classes-cannot-be-called-without-new
++  return new (get())(...Array.from(args || []));
+ });
+
+ test("`new` shouldn't add extra parens", () => ok(new Date().constructor === Date));
+@@ -1115,7 +1118,8 @@ test('#2599: other typed constructors should be inherited', () => {
+   return ok(!((new Base()) instanceof Base));
+ });
+
+-test('#2359: extending native objects that use other typed constructors requires defining a constructor', () => {
++// https://github.com/decaffeinate/decaffeinate/blob/master/docs/correctness-issues.md#subclassing-built-ins-is-allowed-in-different-situations
++skippedTest('#2359: extending native objects that use other typed constructors requires defining a constructor', () => {
+   class BrokenArray extends Array {
+     method() { return 'no one will call me'; }
+   }
+diff --git a/test/cluster.js b/test/cluster.js
+index aa78e2a..2c5a25d 100644
+--- a/test/cluster.js
++++ b/test/cluster.js
+@@ -12,6 +12,10 @@
+
+ if (typeof testingBrowser !== 'undefined' && testingBrowser !== null) { return; }
+
++// CoffeeScript overwrites process.argv, which this test depends on, so manually
++// overwrite it instead.
++process.argv[1] = __filename;
++
+ const cluster = require('cluster');
+
+ if (cluster.isMaster) {
+diff --git a/test/error_messages.js b/test/error_messages.js
+index 18862a4..5c11837 100644
+--- a/test/error_messages.js
++++ b/test/error_messages.js
+@@ -84,7 +84,7 @@ if (typeof require !== 'undefined' && require !== null) {
+
+   test('patchStackTrace line patching', () => {
+     const err = new Error('error');
+-    return ok(err.stack.match(/test[\/\\]error_messages\.coffee:\d+:\d+\b/));
++    return ok(err.stack.match(/test[\/\\]error_messages\.js:\d+:\d+\b/));
+   });
+
+   test('patchStackTrace stack prelude consistent with V8', () => {
+diff --git a/test/functions.js b/test/functions.js
+index b5e72c4..bc03139 100644
+--- a/test/functions.js
++++ b/test/functions.js
+@@ -118,7 +118,8 @@ test('self-referencing functions', () => {
+   return eq(changeMe, 2);
+ });
+
+-test("#2009: don't touch `` `this` ``", () => {
++// https://github.com/decaffeinate/decaffeinate/blob/master/docs/correctness-issues.md#inline-js-that-relies-on-coffeescript-implementation-details-may-not-be-transformed-correctly
++skippedTest("#2009: don't touch `` `this` ``", () => {
+   const nonceA = {};
+   const nonceB = {};
+   let fn = null;
+diff --git a/test/importing.js b/test/importing.js
+index f8dec2a..91e3edd 100644
+--- a/test/importing.js
++++ b/test/importing.js
+@@ -33,7 +33,8 @@ if ((typeof window === 'undefined' || window === null) && (typeof testingBrowser
+     } else {
+       global[magicKey] = {};
+       if ((typeof require !== 'undefined' && require !== null ? require.extensions : undefined) != null) {
+-        ok(require(__filename).method() === magicValue);
++        const requireUncached = require('require-uncached');
++        ok(requireUncached(__filename).method() === magicValue);
+       }
+       return delete global[magicKey];
+     }
+diff --git a/test/operators.js b/test/operators.js
+index 72dec42..0f89850 100644
+--- a/test/operators.js
++++ b/test/operators.js
+@@ -268,7 +268,8 @@ test('#1100: precedence in or-test compilation of `in`', () => {
+   return ok(!([1, 0 || 1].includes(0)));
+ });
+
+-test('#1630: `in` should check `hasOwnProperty`', () => {
++// https://github.com/decaffeinate/decaffeinate/blob/master/docs/correctness-issues.md#undefined-in-arr-returns-true-for-sparse-arrays-without-explicit-undefineds
++skippedTest('#1630: `in` should check `hasOwnProperty`', () => {
+   let needle;
+   return ok((needle = undefined, !Array.from({ length: 1 }).includes(needle)));
+ });
+@@ -471,7 +472,8 @@ test('#3363: Modulo operator coercing order', () => {
+   return eq(5, count);
+ });
+
+-test('#3598: Unary + and - coerce the operand once when it is an identifier', () => {
++// https://github.com/decaffeinate/decaffeinate/blob/master/docs/correctness-issues.md#side-effects-in-valueof-and-getters-may-be-called-multiple-times
++skippedTest('#3598: Unary + and - coerce the operand once when it is an identifier', () => {
+   // Unary + and - do not generate `_ref`s when the operand is a number, for
+   // readability. To make sure that they do when the operand is an identifier,
+   // test that they are consistent with another unary operator as well as another
+diff --git a/test/scope.js b/test/scope.js
+index 2c94e51..d35d984 100644
+--- a/test/scope.js
++++ b/test/scope.js
+@@ -118,19 +118,19 @@ test('loop variable should be accessible after for-from loop', () => {
+   })());
+   return eq(x, 2);
+ });
+-
+-class Array {
++// https://github.com/decaffeinate/decaffeinate/blob/master/docs/correctness-issues.md#globals-like-object-and-array-may-be-accessed-by-name-from-generated-code
++class Array_ {
+   static initClass() {
+     this.prototype.slice = fail;
+   }
+ }
+-Array.initClass(); // needs to be global
+-class Object {
++Array_.initClass(); // needs to be global
++class Object_ {
+   static initClass() {
+     this.prototype.hasOwnProperty = fail;
+   }
+ }
+-Object.initClass();
++Object_.initClass();
+ test("#1973: redefining Array/Object constructors shouldn't confuse __X helpers", () => {
+   const arr = [1, 2, 3, 4];
+   arrayEq([3, 4], arr.slice(2));
+diff --git a/test/support/helpers.js b/test/support/helpers.js
+index 2d0578a..a50a6b7 100644
+--- a/test/support/helpers.js
++++ b/test/support/helpers.js
+@@ -9,6 +9,8 @@
+ */
+ // TODO: This file was created by bulk-decaffeinate.
+ // Fix any style issues and re-enable lint.
++global.skippedTest = function (description, fn) {};
++
+ /*
+  * decaffeinate suggestions:
+  * DS102: Remove unnecessary code created because of implicit returns