implement Scope so we can keep track of references to avoid collisions when generating ids

lib/6to5/file.js

@@ -134,7 +134,19 @@ File.prototype.generate = function () {
   return result;
 };
 
-File.prototype.generateUid = function (name) {
+File.prototype.generateUid = function (name, scope) {
+  if (scope) {
+    var uid;
+    do {
+      uid = this._generateUid(name);
+    } while (scope.has(uid));
+    return uid;
+  } else {
+    return this._generateUid(name);
+  }
+};
+
+File.prototype._generateUid = function (name) {
   // replace all non-valid identifiers with dashes
   name = name.replace(/[^a-zA-Z0-9]/g, "-");
 

lib/6to5/scope.js

@@ -0,0 +1,44 @@
+module.exports = Scope;
+
+var traverse = require("./traverse");
+var t        = require("./types");
+var _        = require("lodash");
+
+function Scope(parent, block) {
+  this.parent = parent;
+
+  var ids = [];
+
+  if (t.isBlockStatement(block)) {
+    _.each(block.body, function (node) {
+      if (t.isVariableDeclaration(node)) {
+        ids = ids.concat(t.getIds(node));
+      }
+    });
+  }
+
+  if (t.isProgram(block) || t.isFunction(block)) {
+    traverse(block, function (node) {
+      if (t.isVariableDeclaration(node)) {
+        ids = ids.concat(t.getIds(node));
+      } else if (t.isFunction(node)) {
+        return false;
+      }
+    });
+  }
+
+  if (t.isFunction(block)) {
+    _.each(block.params, function (param) {
+      ids = ids.concat(t.getIds(param));
+    });
+  }
+
+  this.ids = ids;
+}
+
+Scope.prototype.has = function (id) {
+  if (!id) return false;
+  if (_.contains(this.ids, id)) return true;
+  if (this.parent) return this.parent.has(id);
+  return false;
+};

lib/6to5/transformers/_alias-functions.js

@@ -1,16 +1,16 @@
 var traverse = require("../traverse");
 var t        = require("../types");
 
-var go = function (getBody, node, file) {
+var go = function (getBody, node, file, scope) {
   var argumentsId;
   var thisId;
 
   var getArgumentsId = function () {
-    return argumentsId = argumentsId || t.identifier(file.generateUid("arguments"));
+    return argumentsId = argumentsId || t.identifier(file.generateUid("arguments", scope));
   };
 
   var getThisId = function () {
-    return thisId = thisId || t.identifier(file.generateUid("this"));
+    return thisId = thisId || t.identifier(file.generateUid("this", scope));
   };
 
   // traverse the function and find all alias functions so we can alias
@@ -70,16 +70,16 @@ var go = function (getBody, node, file) {
   }
 };
 
-exports.Program = function (node, parent, file) {
+exports.Program = function (node, parent, file, scope) {
   go(function () {
     return node.body;
-  }, node, file);
+  }, node, file, scope);
 };
 
 exports.FunctionDeclaration =
-exports.FunctionExpression = function (node, parent, file) {
+exports.FunctionExpression = function (node, parent, file, scope) {
   go(function () {
     t.ensureBlock(node);
     return node.body.body;
-  }, node, file);
+  }, node, file, scope);
 };

lib/6to5/transformers/classes.js

@@ -3,14 +3,14 @@ var util     = require("../util");
 var t        = require("../types");
 var _        = require("lodash");
 
-exports.ClassDeclaration = function (node, parent, file) {
+exports.ClassDeclaration = function (node, parent, file, scope) {
   return t.variableDeclaration("var", [
-    t.variableDeclarator(node.id, buildClass(node, file))
+    t.variableDeclarator(node.id, buildClass(node, file, scope))
   ]);
 };
 
-exports.ClassExpression = function (node, parent, file) {
-  return buildClass(node, file);
+exports.ClassExpression = function (node, parent, file, scope) {
+  return buildClass(node, file, scope);
 };
 
 var getMemberExpressionObject = function (node) {
@@ -20,9 +20,9 @@ var getMemberExpressionObject = function (node) {
   return node;
 };
 
-var buildClass = function (node, file) {
+var buildClass = function (node, file, scope) {
   var superName = node.superClass;
-  var className = node.id || t.identifier(file.generateUid("class"));
+  var className = node.id || t.identifier(file.generateUid("class", scope));
 
   var superClassArgument = node.superClass;
   var superClassCallee   = node.superClass;
@@ -32,7 +32,7 @@ var buildClass = function (node, file) {
       superClassArgument = superClassCallee = getMemberExpressionObject(superName);
     } else if (!t.isIdentifier(superName)) {
       superClassArgument = superName;
-      superClassCallee   = superName = t.identifier(file.generateUid("ref"));
+      superClassCallee   = superName = t.identifier(file.generateUid("ref", scope));
     }
   }
 

lib/6to5/transformers/constants.js

@@ -19,7 +19,7 @@ exports.ForStatement = function (node, parent, file) {
   _.each(node.body, function (child) {
     if (child && t.isVariableDeclaration(child) && child.kind === "const") {
       _.each(child.declarations, function (declar) {
-        _.each(util.getIds(declar.id), function (name) {
+        _.each(t.getIds(declar.id), function (name) {
           check(declar, name);
           constants.push(name);
         });

lib/6to5/transformers/destructuring.js

@@ -45,7 +45,7 @@ var pushArrayPattern = function (kind, nodes, pattern, parentId) {
   });
 };
 
-var pushPattern = function (kind, nodes, pattern, parentId, file) {
+var pushPattern = function (kind, nodes, pattern, parentId, file, scope) {
   if (parentId.type !== "MemberExpression" && parentId.type !== "Identifier") {
     var key = t.identifier(file.generateUid("ref"));
 
@@ -60,14 +60,14 @@ var pushPattern = function (kind, nodes, pattern, parentId, file) {
 };
 
 exports.ForInStatement =
-exports.ForOfStatement = function (node, parent, file) {
+exports.ForOfStatement = function (node, parent, file, scope) {
   var declar = node.left;
   if (declar.type !== "VariableDeclaration") return;
 
   var pattern = declar.declarations[0].id;
   if (!t.isPattern(pattern)) return;
 
-  var key = t.identifier(file.generateUid("ref"));
+  var key = t.identifier(file.generateUid("ref", scope));
   node.left = t.variableDeclaration(declar.kind, [
     t.variableDeclarator(key, null)
   ]);
@@ -82,7 +82,7 @@ exports.ForOfStatement = function (node, parent, file) {
   block.body = nodes.concat(block.body);
 };
 
-exports.Function = function (node, parent, file) {
+exports.Function = function (node, parent, file, scope) {
   var nodes = [];
 
   var hasDestructuring = false;
@@ -91,8 +91,8 @@ exports.Function = function (node, parent, file) {
     if (!t.isPattern(pattern)) return pattern;
 
     hasDestructuring = true;
-    var parentId = t.identifier(file.generateUid("ref"));
-    pushPattern("var", nodes, pattern, parentId, file);
+    var parentId = t.identifier(file.generateUid("ref", scope));
+    pushPattern("var", nodes, pattern, parentId, file, scope);
     return parentId;
   });
 
@@ -104,7 +104,7 @@ exports.Function = function (node, parent, file) {
   block.body = nodes.concat(block.body);
 };
 
-exports.ExpressionStatement = function (node, parent, file) {
+exports.ExpressionStatement = function (node, parent, file, scope) {
   var expr = node.expression;
   if (expr.type !== "AssignmentExpression") return;
 
@@ -112,7 +112,7 @@ exports.ExpressionStatement = function (node, parent, file) {
 
   var nodes = [];
 
-  var ref = t.identifier(file.generateUid("ref"));
+  var ref = t.identifier(file.generateUid("ref", scope));
   nodes.push(t.variableDeclaration("var", [
     t.variableDeclarator(ref, expr.right)
   ]));
@@ -122,7 +122,7 @@ exports.ExpressionStatement = function (node, parent, file) {
   return nodes;
 };
 
-exports.VariableDeclaration = function (node, parent, file) {
+exports.VariableDeclaration = function (node, parent, file, scope) {
   if (t.isForInStatement(parent)) return;
 
   var nodes = [];
@@ -140,7 +140,7 @@ exports.VariableDeclaration = function (node, parent, file) {
     var patternId = declar.init;
     var pattern   = declar.id;
     if (t.isPattern(pattern) && patternId) {
-      pushPattern(node.kind, nodes, pattern, patternId, file);
+      pushPattern(node.kind, nodes, pattern, patternId, file, scope);
     } else {
       nodes.push(buildVariableAssign(node.kind, declar.id, declar.init));
     }

lib/6to5/transformers/for-of.js

@@ -1,11 +1,11 @@
 var util = require("../util");
 var t    = require("../types");
 
-exports.ForOfStatement = function (node, parent, file) {
+exports.ForOfStatement = function (node, parent, file, scope) {
   var left = node.left;
   var declar;
 
-  var stepKey = t.identifier(file.generateUid("step"));
+  var stepKey = t.identifier(file.generateUid("step", scope));
   var stepValueId = t.memberExpression(stepKey, t.identifier("value"));
 
   if (t.isIdentifier(left)) {
@@ -19,7 +19,7 @@ exports.ForOfStatement = function (node, parent, file) {
   }
 
   var node2 = util.template("for-of", {
-    ITERATOR_KEY: file.generateUid("iterator"),
+    ITERATOR_KEY: file.generateUid("iterator", scope),
     STEP_KEY:     stepKey,
     OBJECT:       node.right
   });

lib/6to5/types/alias-keys.json

@@ -1,7 +1,10 @@
 {
-  "ArrowFunctionExpression": ["Function"],
-  "FunctionDeclaration":     ["Function"],
-  "FunctionExpression":      ["Function"],
+  "ArrowFunctionExpression": ["Scope", "Function"],
+  "FunctionDeclaration":     ["Scope", "Function"],
+  "FunctionExpression":      ["Scope", "Function"],
+
+  "BlockStatement": ["Scope"],
+  "Program":        ["Scope"],
 
   "LogicalExpression": ["Binary"],
   "BinaryExpression":  ["Binary"],