Fix for node modules

lib/src/compiler/module_builder.dart

 // Copyright (c) 2015, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 import 'package:path/path.dart' as path;
 
 import '../js_ast/js_ast.dart';
 import 'js_names.dart';
 
 /// Base class for compiling ES6 modules into various ES5 module patterns.
@@ skipping 86 matching lines @@
           "Imports", new ArrayInitializer(importNames, multiline: true)),
       resultModule
     ]);
     return new Program(<ModuleItem>[moduleDef]);
   }
 }
 
 /// Generates node modules.
 class NodeModuleBuilder extends _ModuleBuilder {
   Program build(Program module) {
-    var importStatements = [js.statement("'use strict';"),];
+    var importStatements = [];
+
+    // Collect imports/exports/statements.
+    visitProgram(module);
 
     for (var import in imports) {
       // TODO(jmesserly): we could use destructuring once Atom supports it.
       var moduleVar =
           new TemporaryId(pathToJSIdentifier(import.from.valueWithoutQuotes));
       importStatements
           .add(js.statement('const # = require(#);', [moduleVar, import.from]));
 
       // TODO(jmesserly): optimize for the common case of a single import.
       for (var importName in import.namedImports) {
@@ skipping 10 matching lines @@
       statements.add(js.comment('Exports:'));
       for (var export in exports) {
         var names = export.exportedNames;
         assert(names != null); // export * not supported in legacy modules.
         for (var name in names) {
           statements
               .add(js.statement('#.# = #;', [exportsVar, name.name, name]));
         }
       }
     }
-    return new Program(statements);
+
+    var block =

[vsm, 2016/04/18 13:38:25]

Not entirely sure why I seem to need this.  Without it, it seems js_ast wasn't
renaming colliding identifiers.  I'd get redundant declarations in the SDK:

  const _add = Symbol('_add');
  ...
  const _add = Symbol('_add');

By nesting the whole thing, I'd see:

  const _add = Symbol('_add');
  ...
  const _add$ = Symbol('_add');

Is js_ast not renaming at the top-level?

[Jennifer Messerly, 2016/04/18 20:52:18]

Yeah seems like it's skipping the top-level. That's probably an easy fix though.

Do you mind taking a look? IMO, it'd be good to understand what's going on,
rather than work around it.

Could be a TODO as well. But it'd be nice to keep the technical debt low (I'm
still recovering from the last big cleanup ;)... not to mention our runtime/SDK
debt.)

[vsm, 2016/04/19 21:28:29]

Added a TODO and filed a bug for now.

+        js.statement("(function() { 'use strict'; #; })()", [statements]);
+
+    return new Program([block]);
   }
 }
 
 /// Escape [name] to make it into a valid identifier.
 String pathToJSIdentifier(String name) {
   name = path.basenameWithoutExtension(name);
   if (name.length == 0) return r'$';
 
   // Escape any invalid characters
   StringBuffer buffer = null;
@@ skipping 12 matching lines @@
   // Ensure the identifier first character is not numeric and that the whole
   // identifier is not a keyword.
   if (result.startsWith(new RegExp('[0-9]')) || invalidVariableName(result)) {
     return '\$$result';
   }
   return result;
 }
 
 // Invalid characters for identifiers, which would need to be escaped.
 final _invalidCharInIdentifier = new RegExp(r'[^A-Za-z_$0-9]');