add file alias declarations so we can alias certain long function calls - resolves #62

lib/6to5/declarations.js

@@ -0,0 +1,3 @@
+var b = require("recast").types.builders;
+
+exports.slice = b.memberExpression(b.identifier("Array"), b.memberExpression(b.identifier("prototype"), b.identifier("slice"), false), false)

lib/6to5/file.js

@@ -2,14 +2,17 @@ module.exports = File;
 
 var SHEBANG_REGEX = /^\#\!.*/;
 
-var transform = require("./transform");
-var util      = require("./util");
-var _         = require("lodash");
+var declarations = require("./declarations");
+var transform    = require("./transform");
+var util         = require("./util");
+var b            = require("recast").types.builders;
+var _            = require("lodash");
 
 function File(opts) {
-  this.uids = {};
-  this.opts = File.normaliseOptions(opts);
-  this.ast  = {};
+  this.declarations = {};
+  this.uids         = {};
+  this.opts         = File.normaliseOptions(opts);
+  this.ast          = {};
 }
 
 File.normaliseOptions = function (opts) {
@@ -46,6 +49,18 @@ File.prototype.parseShebang = function (code) {
   return code;
 };
 
+File.prototype.addDeclaration = function (name) {
+  var declar = this.declarations[name];
+  if (declar) return declar.uid;
+
+  var uid = b.identifier(this.generateUid(name));
+  this.declarations[name] = {
+    uid: uid,
+    node: declarations[name]
+  };
+  return uid;
+};
+
 File.prototype.parse = function (code) {
   var self = this;
 
@@ -66,6 +81,14 @@ File.prototype.transform = function (ast) {
     transformer.transform(self);
   });
 
+  var body = ast.program.body;
+
+  _.each(this.declarations, function (declar) {
+    body.unshift(b.variableDeclaration("var", [
+      b.variableDeclarator(declar.uid, declar.node)
+    ]));
+  });
+
   var result = util.generate(ast, opts);
 
   if (this.shebang) {

lib/6to5/templates/arguments-slice-assign-arg.js

@@ -1 +1 @@
-var VARIABLE_NAME = Array.prototype.slice.call(arguments, SLICE_ARG);
+var VARIABLE_NAME = SLICE_KEY.call(arguments, SLICE_ARG);

lib/6to5/templates/arguments-slice-assign.js

@@ -1 +1 @@
-var VARIABLE_NAME = Array.prototype.slice.call(arguments);
+var VARIABLE_NAME = SLICE_KEY.call(arguments);

lib/6to5/templates/arguments-slice.js

@@ -1 +1 @@
-Array.prototype.slice.call(arguments);
+SLICE_KEY.call(arguments);

lib/6to5/transformers/rest-parameters.js

@@ -1,7 +1,7 @@
 var util = require("../util");
 var b    = require("recast").types.builders;
 
-exports.Function = function (node) {
+exports.Function = function (node, parent, file) {
   if (!node.rest) return;
 
   var rest = node.rest;
@@ -12,6 +12,7 @@ exports.Function = function (node) {
 
   util.ensureBlock(node);
   node.body.body.unshift(util.template(templateName, {
+    SLICE_KEY: file.addDeclaration("slice"),
     VARIABLE_NAME: rest,
     SLICE_ARG: b.literal(node.params.length)
   }));

lib/6to5/transformers/spread.js

@@ -21,7 +21,7 @@ exports.ArrayExpression = function (node) {
   return concat;
 };
 
-exports.CallExpression = function (node) {
+exports.CallExpression = function (node, parent, file) {
   var args = node.arguments;
 
   if (args.length && _.last(args).type === "SpreadElement") {
@@ -34,7 +34,9 @@ exports.CallExpression = function (node) {
 
     if (args.length) {
       if (spreadLiteral.name === "arguments") {
-        spreadLiteral = util.template("arguments-slice");
+        spreadLiteral = util.template("arguments-slice", {
+          SLICE_KEY: file.addDeclaration("slice")
+        });
       }
 
       var concat = util.template("array-concat");

test/fixtures/syntax/rest-parameters/multiple/expected.js

@@ -1,7 +1,9 @@
+var _slice = Array.prototype.slice;
+
 var t = function (f) {
-  var items = Array.prototype.slice.call(arguments, 1);
+  var items = _slice.call(arguments, 1);
 };
 
 function t(f) {
-  var items = Array.prototype.slice.call(arguments, 1);
+  var items = _slice.call(arguments, 1);
 }

test/fixtures/syntax/rest-parameters/single/expected.js

@@ -1,7 +1,9 @@
+var _slice = Array.prototype.slice;
+
 var t = function () {
-  var items = Array.prototype.slice.call(arguments);
+  var items = _slice.call(arguments);
 };
 
 function t() {
-  var items = Array.prototype.slice.call(arguments);
+  var items = _slice.call(arguments);
 }

test/fixtures/syntax/spread/arguments/expected.js

@@ -1,5 +1,7 @@
+var _slice = Array.prototype.slice;
+
 function foo() {
-  return bar.apply(null, ["test"].concat(Array.prototype.slice.call(arguments)));
+  return bar.apply(null, ["test"].concat(_slice.call(arguments)));
 }
 function bar(one, two, three) {
   return [