add destructuring support

lib/6to5/templates/variable-assign.js

@@ -0,0 +1 @@
+var KEY = VALUE;

lib/6to5/transformers/destructuring.js

@@ -0,0 +1,112 @@
+var util = require("../util");
+var _    = require("lodash");
+
+var isPattern = function (id) {
+  return id.type === "ArrayPattern" || id.type === "ObjectPattern";
+};
+
+exports.VariableDeclaration = function (node, parent, opts, generateUid) {
+  var nodes = [];
+
+  var hasPattern = false;
+  _.each(node.declarations, function (declar) {
+    if (isPattern(declar.id)) {
+      hasPattern = true;
+      return false;
+    }
+  });
+  if (!hasPattern) return;
+
+  //
+
+  var buildVariableAssign = function (id, init) {
+    return {
+      type: "VariableDeclaration",
+      kind: node.kind,
+      declarations: [{
+        type: "VariableDeclarator",
+        id: id,
+        init: 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 = {
+        type: "MemberExpression",
+        object: parentId,
+        property: prop.key
+      };
+
+      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 = {
+        type: "MemberExpression",
+        computed: true,
+        object: parentId,
+        property: {
+          type: "Literal",
+          value: i
+        }
+      };
+
+      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 = {
+        type: "Identifier",
+        name: key
+      };
+    }
+
+    push(id, init);
+  };
+
+  //
+
+  _.each(node.declarations, function (declar) {
+    var init = declar.init;
+    var id   = declar.id;
+
+    if (isPattern(id)) {
+      pushPattern(id, init);
+    } else {
+      nodes.push(buildVariableAssign(id, init));
+    }
+  });
+
+  return nodes;
+};