support destructuring in parameter lists - closes #19

lib/6to5/transformers/destructuring.js

@@ -6,6 +6,81 @@ var isPattern = function (id) {
   return id.type === "ArrayPattern" || id.type === "ObjectPattern";
 };
 
+
+var buildVariableAssign = function (kind, id, init) {
+  return b.variableDeclaration(kind, [
+    b.variableDeclarator(id, init)
+  ]);
+};
+
+var push = function (kind, nodes, pattern, parentId) {
+  if (pattern.type === "ObjectPattern") {
+    pushObjectPattern(kind, nodes, pattern, parentId);
+  } else if (pattern.type === "ArrayPattern") {
+    pushArrayPattern(kind, nodes, pattern, parentId);
+  }
+};
+
+var pushObjectPattern = function (kind, nodes, pattern, parentId) {
+  _.each(pattern.properties, function (prop) {
+    var pattern2   = prop.value;
+    var patternId2 = b.memberExpression(parentId, prop.key, false);
+
+    if (isPattern(pattern2)) {
+      push(kind, nodes, pattern2, patternId2);
+    } else {
+      nodes.push(buildVariableAssign(kind, pattern2, patternId2));
+    }
+  });
+};
+
+var pushArrayPattern = function (kind, nodes, pattern, parentId) {
+  _.each(pattern.elements, function (elem, i) {
+    if (!elem) return;
+
+    var newPatternId = b.memberExpression(parentId, b.literal(i), true);
+
+    if (elem.type === "Identifier") {
+      nodes.push(buildVariableAssign(kind, elem, newPatternId));
+    } else {
+      push(kind, nodes, elem, newPatternId);
+    }
+  });
+};
+
+var pushPattern = function (kind, nodes, pattern, parentId, generateUid) {
+  if (parentId.type !== "MemberExpression" && parentId.type !== "Identifier") {
+    var key = generateUid("ref");
+
+    nodes.push(util.template("variable-assign", {
+      KEY: key,
+      VALUE: parentId
+    }, true));
+
+    parentId = b.identifier(key);
+  }
+
+  push(kind, nodes, pattern, parentId);
+};
+
+exports.FunctionDeclaration =
+exports.FunctionExpression = function (node, parent, opts, generateUid) {
+  var block = node.body;
+  var nodes = [];
+
+  node.params = node.params.map(function (pattern) {
+    if (!isPattern(pattern)) return pattern;
+
+    var parentId = b.identifier(generateUid("ref"));
+
+    pushPattern("var", nodes, pattern, parentId, generateUid);
+
+    return parentId;
+  });
+
+  block.body = nodes.concat(block.body);
+};
+
 exports.VariableDeclaration = function (node, parent, opts, generateUid) {
   var nodes = [];
 
@@ -18,73 +93,13 @@ exports.VariableDeclaration = function (node, parent, opts, generateUid) {
   });
   if (!hasPattern) return;
 
-  //
-
-  var buildVariableAssign = function (id, init) {
-    return b.variableDeclaration(node.kind, [
-      b.variableDeclarator(id, init)
-    ]);
-  };
-
-  var push = function (pattern, parentId) {
-    if (pattern.type === "ObjectPattern") {
-      pushObjectPattern(pattern, parentId);
-    } else if (pattern.type === "ArrayPattern") {
-      pushArrayPattern(pattern, parentId);
-    }
-  };
-
-  var pushObjectPattern = function (pattern, parentId) {
-    _.each(pattern.properties, function (prop) {
-      var id = prop.value;
-
-      var init = b.memberExpression(parentId, prop.key, false);
-
-      if (isPattern(id)) {
-        push(id, init);
-      } else {
-        nodes.push(buildVariableAssign(id, init));
-      }
-    });
-  };
-
-  var pushArrayPattern = function (pattern, parentId) {
-    _.each(pattern.elements, function (id, i) {
-      var init = b.memberExpression(parentId, b.literal(i), true);
-
-      if (id.type === "Identifier") {
-        nodes.push(buildVariableAssign(id, init));
-      } else {
-        push(id, init);
-      }
-    });
-  };
-
-  var pushPattern = function (id, init) {
-    if (init.type !== "MemberExpression" && init.type !== "Identifier") {
-      var key = generateUid("ref");
-
-      nodes.push(util.template("variable-assign", {
-        KEY: key,
-        VALUE: init
-      }, true));
-
-      init = b.identifier(key);
-    }
-
-    push(id, init);
-  };
-
-  //
-
   _.each(node.declarations, function (declar) {
-    var init = declar.init;
-    var id   = declar.id;
-
-    if (isPattern(id)) {
-      pushPattern(id, init);
+    var patternId = declar.init;
+    var pattern   = declar.id;
+    if (isPattern(pattern)) {
+      pushPattern(node.kind, nodes, pattern, patternId, generateUid);
     } else {
-      nodes.push(buildVariableAssign(id, init));
+      nodes.push(buildVariableAssign(node.kind, declar.id, declar.init));
     }
   });
 

test/fixtures/destructuring/parameters/actual.js

@@ -0,0 +1,15 @@
+function somethingAdvanced({topLeft: {x: x1, y: y1}, bottomRight: {x: x2, y: y2}}){
+
+}
+
+function unpackObject({title: title, author: author}) {
+  return title + ' ' + author;
+}
+
+console.log(unpackObject({title: 'title', author: 'author'}));
+
+var unpackArray = function ([a, b, c], [x, y, z]) {
+  return a+b+c;
+};
+
+console.log(unpackArray(['hello', ', ', 'world'], [1, 2, 3]));

test/fixtures/destructuring/parameters/expected.js

@@ -0,0 +1,28 @@
+function somethingAdvanced(_ref){
+  var x1 = _ref.topLeft.x;
+  var y1 = _ref.topLeft.y;
+  var x2 = _ref.bottomRight.x;
+  var y2 = _ref.bottomRight.y;
+}
+
+function unpackObject(_ref2) {
+  var title = _ref2.title;
+  var author = _ref2.author;
+  return title + ' ' + author;
+}
+
+console.log(unpackObject({title: 'title', author: 'author'}));
+
+var unpackArray = function (_ref3, _ref4) {
+  var a = _ref3[0];
+  var b = _ref3[1];
+  var c = _ref3[2];
+
+  var x = _ref4[0];
+  var y = _ref4[1];
+  var z = _ref4[2];
+
+  return a + b + c;
+};
+
+console.log(unpackArray(['hello', ', ', 'world'], [1, 2, 3]));