From 9dd65c809f884d320355ebbe6163a1b43454f2a3 Mon Sep 17 00:00:00 2001
From: Brian Ng <bng412@gmail.com>
Date: Thu, 3 Aug 2017 22:27:30 -0500
Subject: [PATCH] fixes

---
 .../src/index.js                              |  2 +-
 .../src/params.js                             | 50 ++++++++++++++++++-
 .../parameters/rest-nested-5656/expected.js   |  2 +-
 .../object-rest/parameters/expected.js        | 12 ++---
 4 files changed, 57 insertions(+), 9 deletions(-)

diff --git a/packages/babel-plugin-transform-es2015-parameters/src/index.js b/packages/babel-plugin-transform-es2015-parameters/src/index.js
index 267c5f13b6..af12fa0399 100644
--- a/packages/babel-plugin-transform-es2015-parameters/src/index.js
+++ b/packages/babel-plugin-transform-es2015-parameters/src/index.js
@@ -16,7 +16,7 @@ export default function() {
         }
 
         const convertedRest = convertFunctionRest(path);
-        const convertedParams = convertFunctionParams(path);
+        const convertedParams = convertFunctionParams(path, this.opts.loose);
 
         if (convertedRest || convertedParams) {
           // Manually reprocess this scope to ensure that the moved params are updated.
diff --git a/packages/babel-plugin-transform-es2015-parameters/src/params.js b/packages/babel-plugin-transform-es2015-parameters/src/params.js
index de87c35d8f..73215cbd09 100644
--- a/packages/babel-plugin-transform-es2015-parameters/src/params.js
+++ b/packages/babel-plugin-transform-es2015-parameters/src/params.js
@@ -10,6 +10,16 @@ const buildDefaultParam = template(`
       DEFAULT_VALUE;
 `);
 
+const buildLooseDefaultParam = template(`
+  if (ASSIGNMENT_IDENTIFIER === UNDEFINED) {
+    ASSIGNMENT_IDENTIFIER = DEFAULT_VALUE;
+  }
+`);
+
+const buildLooseDestructuredDefaultParam = template(`
+  let ASSIGNMENT_IDENTIFIER = PARAMETER_NAME === UNDEFINED ? DEFAULT_VALUE : PARAMETER_NAME ;
+`);
+
 const buildArgumentsAccess = template(`
   let $0 = arguments[$1];
 `);
@@ -35,7 +45,7 @@ const iifeVisitor = {
   },
 };
 
-export default function convertFunctionParams(path) {
+export default function convertFunctionParams(path, loose) {
   const { node, scope } = path;
 
   const state = {
@@ -49,6 +59,44 @@ export default function convertFunctionParams(path) {
 
   //
   const params = path.get("params");
+
+  if (loose) {
+    const body = [];
+    for (let i = 0; i < params.length; ++i) {
+      const param = params[i];
+      if (param.isAssignmentPattern()) {
+        const left = param.get("left");
+        const right = param.get("right");
+
+        const undefinedNode = scope.buildUndefinedNode();
+
+        if (left.isIdentifier()) {
+          body.push(
+            buildLooseDefaultParam({
+              ASSIGNMENT_IDENTIFIER: left.node,
+              DEFAULT_VALUE: right.node,
+              UNDEFINED: undefinedNode,
+            }),
+          );
+          param.replaceWith(left.node);
+        } else if (left.isObjectPattern() || left.isArrayPattern()) {
+          const paramName = scope.generateUidIdentifier();
+          body.push(
+            buildLooseDestructuredDefaultParam({
+              ASSIGNMENT_IDENTIFIER: left.node,
+              DEFAULT_VALUE: right.node,
+              PARAMETER_NAME: paramName,
+              UNDEFINED: undefinedNode,
+            }),
+          );
+          param.replaceWith(paramName);
+        }
+      }
+    }
+    path.get("body").unshiftContainer("body", body);
+    return;
+  }
+
   for (let i = 0; i < params.length; i++) {
     const param = params[i];
 
diff --git a/packages/babel-plugin-transform-es2015-parameters/test/fixtures/parameters/rest-nested-5656/expected.js b/packages/babel-plugin-transform-es2015-parameters/test/fixtures/parameters/rest-nested-5656/expected.js
index c0d587ed6e..1a76699de9 100644
--- a/packages/babel-plugin-transform-es2015-parameters/test/fixtures/parameters/rest-nested-5656/expected.js
+++ b/packages/babel-plugin-transform-es2015-parameters/test/fixtures/parameters/rest-nested-5656/expected.js
@@ -28,7 +28,7 @@ function d(thing) {
   };
 
   {
-    var _args = thing;
+    var args = thing;
     foo(thing);
   }
 }
diff --git a/packages/babel-plugin-transform-object-rest-spread/test/fixtures/object-rest/parameters/expected.js b/packages/babel-plugin-transform-object-rest-spread/test/fixtures/object-rest/parameters/expected.js
index a24b010661..39cbd5c047 100644
--- a/packages/babel-plugin-transform-object-rest-spread/test/fixtures/object-rest/parameters/expected.js
+++ b/packages/babel-plugin-transform-object-rest-spread/test/fixtures/object-rest/parameters/expected.js
@@ -17,15 +17,15 @@ function a3(_ref3) {
       c2 = babelHelpers.objectWithoutProperties(_ref3, ["a2", "b2"]);
 }
 
-function a4(_ref4, _ref5) {
-  let {
-    a5
-  } = _ref5,
-      c5 = babelHelpers.objectWithoutProperties(_ref5, ["a5"]);
+function a4(_ref5, _ref4) {
   let {
     a3
+  } = _ref5,
+      c3 = babelHelpers.objectWithoutProperties(_ref5, ["a3"]);
+  let {
+    a5
   } = _ref4,
-      c3 = babelHelpers.objectWithoutProperties(_ref4, ["a3"]);
+      c5 = babelHelpers.objectWithoutProperties(_ref4, ["a5"]);
 }
 
 function a5(_ref6) {