From a20a5e15aa4c2a268b4ff9982aeb5459716da7e8 Mon Sep 17 00:00:00 2001
From: cpojer <christoph.pojer@gmail.com>
Date: Fri, 22 May 2015 18:11:57 -0700
Subject: [PATCH] Add transform to fix up misuse of arguments in arrow
 functions.

---
 test/__tests__/transform-tests.js            |  4 +
 test/arrow-function-arguments-test.js        | 28 +++++++
 test/arrow-function-arguments-test.output.js | 28 +++++++
 transforms/arrow-function-arguments.js       | 84 ++++++++++++++++++++
 4 files changed, 144 insertions(+)
 create mode 100644 test/arrow-function-arguments-test.js
 create mode 100644 test/arrow-function-arguments-test.output.js
 create mode 100644 transforms/arrow-function-arguments.js

diff --git a/test/__tests__/transform-tests.js b/test/__tests__/transform-tests.js
index b950f7b..76b7b2a 100644
--- a/test/__tests__/transform-tests.js
+++ b/test/__tests__/transform-tests.js
@@ -56,4 +56,8 @@ describe('Transform Tests', () => {
     test('insert-super', 'insert-super-test');
   });
 
+  it('transforms the "arrow function arguments" tests correctly', () => {
+    test('arrow-function-arguments', 'arrow-function-arguments-test');
+  });
+
 });
diff --git a/test/arrow-function-arguments-test.js b/test/arrow-function-arguments-test.js
new file mode 100644
index 0000000..1b44b50
--- /dev/null
+++ b/test/arrow-function-arguments-test.js
@@ -0,0 +1,28 @@
+'use strict';
+
+var fn1 = () => console.log(arguments);
+
+var fn2 = (a, b, c) => {
+  console.log(arguments);
+
+  return arguments;
+};
+
+var fn3 = (a, b, args) => {
+  console.log(args);
+
+  return arguments;
+};
+
+var fn4 = function(a, b, c) {
+  console.log(arguments);
+  var fn5 = () => arguments;
+  var fn6 = () => (function() { return arguments; });
+  class A {
+    constructor() {
+      console.log(arguments);
+    }
+  }
+};
+
+var fn5 = (a, ...b) => arguments;
diff --git a/test/arrow-function-arguments-test.output.js b/test/arrow-function-arguments-test.output.js
new file mode 100644
index 0000000..16c144f
--- /dev/null
+++ b/test/arrow-function-arguments-test.output.js
@@ -0,0 +1,28 @@
+'use strict';
+
+var fn1 = (...args) => console.log(args);
+
+var fn2 = (a, b, c, ...args) => {
+  console.log([a, b, c, ...args]);
+
+  return [a, b, c, ...args];
+};
+
+var fn3 = (a, b, args) => {
+  console.log(args);
+
+  return arguments;
+};
+
+var fn4 = function(a, b, c) {
+  console.log(arguments);
+  var fn5 = (...args) => args;
+  var fn6 = () => (function() { return arguments; });
+  class A {
+    constructor() {
+      console.log(arguments);
+    }
+  }
+};
+
+var fn5 = (a, ...b) => [a, ...b];
diff --git a/transforms/arrow-function-arguments.js b/transforms/arrow-function-arguments.js
new file mode 100644
index 0000000..a5ab957
--- /dev/null
+++ b/transforms/arrow-function-arguments.js
@@ -0,0 +1,84 @@
+// -----------------------------------------------------------------------------
+// Update arrow function arguments to args
+function arrowFunctionArguments(file, api, options) {
+  const j = api.jscodeshift;
+
+  const printOptions = options.printOptions || {quote: 'single'};
+  const root = j(file.source);
+
+  const ARGUMENTS = 'arguments';
+  const ARGS = 'args';
+
+  const createArrowFunctionExpression = (fn, args) => {
+    const arrow = j.arrowFunctionExpression(
+      (fn.params || []).concat(
+        // https://github.com/benjamn/recast/pull/179
+        // j.spreadElementPattern(args)
+      ),
+      fn.body,
+      fn.generator
+    );
+    arrow.rest = args;
+    return arrow;
+  };
+
+  const filterArrowFunctions = path => {
+    while (path.parent) {
+      switch (path.value.type) {
+        case 'ArrowFunctionExpression':
+          if (j(path).find(j.Identifier, {name: ARGS}).size()) {
+            console.error(
+              file.path + ': arrow function uses "' + ARGS + '" already. ' +
+              'Please rename this identifier first.'
+            );
+            return false;
+          }
+          return true;
+        case 'FunctionExpression':
+        case 'MethodDeclaration':
+        case 'Function':
+        case 'FunctionDeclaration':
+          return false;
+        default:
+          break;
+      }
+      path = path.parent;
+    }
+    return false;
+  };
+
+  const updateArgumentsCalls = path => {
+    var afPath = path;
+    while (afPath.parent) {
+      if (afPath.value.type == 'ArrowFunctionExpression') {
+        break;
+      }
+      afPath = afPath.parent;
+    }
+
+    const {value: fn} = afPath;
+    const {params} = fn;
+    const args = fn.rest || j.identifier(ARGS);
+    j(afPath).replaceWith(createArrowFunctionExpression(fn, args));
+
+    if (params.length) {
+      j(path).replaceWith(
+        j.arrayExpression(params.concat(
+          j.spreadElement(args)
+        ))
+      );
+    } else {
+      j(path).replaceWith(args);
+    }
+  };
+
+  const didTransform = root
+    .find(j.Identifier, {name: ARGUMENTS})
+    .filter(filterArrowFunctions)
+    .forEach(updateArgumentsCalls)
+    .size() > 0;
+
+  return didTransform ? root.toSource(printOptions) + '\n' : null;
+}
+
+module.exports = arrowFunctionArguments;