Initial --modules=es6 support

lib/src/codegen/js_codegen.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.
 
 library dev_compiler.src.codegen.js_codegen;
 
 import 'dart:collection' show HashSet, HashMap, SplayTreeSet;
 
 import 'package:analyzer/analyzer.dart' hide ConstantEvaluator;
 import 'package:analyzer/src/generated/ast.dart' hide ConstantEvaluator;
@@ skipping 20 matching lines @@
 import '../utils.dart';
 
 import 'code_generator.dart';
 import 'js_field_storage.dart';
 import 'js_interop.dart';
 import 'js_names.dart' as JS;
 import 'js_metalet.dart' as JS;
 import 'js_module_item_order.dart';
 import 'js_names.dart';
 import 'js_printer.dart' show writeJsLibrary;
+import 'module_builder.dart';
 import 'side_effect_analysis.dart';
 
 // Various dynamic helpers we call.
 // If renaming these, make sure to check other places like the
 // _runtime.js file and comments.
 // TODO(jmesserly): ideally we'd have a "dynamic call" dart library we can
 // import and generate calls to, rather than dart_runtime.js
 const DPUT = 'dput';
 const DLOAD = 'dload';
 const DINDEX = 'dindex';
@@ skipping 120 matching lines @@
     _flushLibraryProperties(_moduleItems);
 
     // Mark all qualified names as qualified or not, depending on if they need
     // to be loaded lazily or not.
     for (var elementIdPairs in _qualifiedIds) {
       var element = elementIdPairs.e0;
       var id = elementIdPairs.e1;
       id.setQualified(!_loader.isLoaded(element));
     }
 
-    if (_exports.isNotEmpty) _moduleItems.add(js.comment('Exports:'));
+    var moduleBuilder = new ModuleBuilder(
+        compiler.getModuleName(currentLibrary.source.uri),
+        _jsModuleValue,
+        _exportsVar,
+        options.moduleFormat);
 
-    // TODO(jmesserly): make these immutable in JS?
-    for (var name in _exports) {
-      _moduleItems.add(js.statement('#.# = #;', [_exportsVar, name, name]));
-    }
+    _exports.forEach(moduleBuilder.addExport);
 
-    var jsPath = compiler.getModuleName(currentLibrary.source.uri);
-
-    // TODO(jmesserly): it would be great to run the renamer on the body,
-    // then figure out if we really need each of these parameters.
-    // See ES6 modules: https://github.com/dart-lang/dev_compiler/issues/34
-    var params = [_exportsVar];
-    var lazyParams = [];
-
-    var imports = <JS.Expression>[];
-    var lazyImports = <JS.Expression>[];
-    var moduleStatements = <JS.Statement>[];
-
-    addImport(String name, JS.Expression libVar, {bool lazy: false}) {
-      (lazy ? lazyImports : imports).add(js.string(name, "'"));
-      (lazy ? lazyParams : params).add(libVar);
-    }
-
+    var items = <JS.ModuleItem>[];
     if (!_isDartRuntime) {
-      addImport('dart/_runtime', _runtimeLibVar);
+      moduleBuilder.addImport('dart/_runtime', _runtimeLibVar);
 
       var dartxImport =
           js.statement("let # = #.dartx;", [_dartxVar, _runtimeLibVar]);
-      moduleStatements.add(dartxImport);
+      items.add(dartxImport);
     }
+    items.addAll(_moduleItems);
+
     _imports.forEach((LibraryElement lib, JS.TemporaryId temp) {
-      addImport(compiler.getModuleName(lib.source.uri), temp,
-          lazy: _isDartRuntime || !_loader.libraryIsLoaded(lib));
+      moduleBuilder.addImport(compiler.getModuleName(lib.source.uri), temp,
+          isLazy: _isDartRuntime || !_loader.libraryIsLoaded(lib));
     });
-    params.addAll(lazyParams);
-
-    moduleStatements.addAll(_moduleItems);
-
-    var module =
-        js.call("function(#) { 'use strict'; #; }", [params, moduleStatements]);
-
-    var moduleDef = js.statement("dart_library.library(#, #, #, #, #)", [
-      js.string(jsPath, "'"),
-      _jsModuleValue ?? new JS.LiteralNull(),
-      js.commentExpression(
-          "Imports", new JS.ArrayInitializer(imports, multiline: true)),
-      js.commentExpression("Lazy imports",
-          new JS.ArrayInitializer(lazyImports, multiline: true)),
-      module
-    ]);
 
     // TODO(jmesserly): scriptTag support.
     // Enable this if we know we're targetting command line environment?
     // It doesn't work in browser.
     // var jsBin = compiler.options.runnerOptions.v8Binary;
     // String scriptTag = null;
     // if (library.library.scriptTag != null) scriptTag = '/usr/bin/env $jsBin';
-    return new JS.Program(<JS.Statement>[moduleDef]);
+    return moduleBuilder.build(items);
   }
 
   void _emitModuleItem(AstNode node) {
     // Attempt to group adjacent fields/properties.
     if (node is! VariableDeclaration) _flushLazyFields(_moduleItems);
     if (node is! FunctionDeclaration) _flushLibraryProperties(_moduleItems);
 
     var code = _visit(node);
     if (code != null) _moduleItems.add(code);
   }
@@ skipping 3370 matching lines @@
 
 /// A special kind of element created by the compiler, signifying a temporary
 /// variable. These objects use instance equality, and should be shared
 /// everywhere in the tree where they are treated as the same variable.
 class TemporaryVariableElement extends LocalVariableElementImpl {
   TemporaryVariableElement.forNode(Identifier name) : super.forNode(name);
 
   int get hashCode => identityHashCode(this);
   bool operator ==(Object other) => identical(this, other);
 }