feat(dart/transform): Allow multiple transformer entry points

- Allow the user to specify multiple entry points to an app.
- Allow the Angular 2 transformer to run without explicit entry points to
generate necessary setters & getters on built-in directives like `For`
and `If`.

Closes #1246

modules/angular2/src/transform/reflection_remover/codegen.dart

@@ -12,14 +12,14 @@ class Codegen {
 
   /// The prefix used to import our generated file.
   final String prefix;
-  /// The import uri
-  final String importUri;
+  /// The import uris
+  final Iterable<String> importUris;
 
-  Codegen(String reflectionEntryPointPath, String newEntryPointPath,
+  Codegen(String reflectionEntryPointPath, Iterable<String> newEntryPointPaths,
       {String prefix})
       : this.prefix = prefix == null ? _PREFIX_BASE : prefix,
-        importUri = path.relative(newEntryPointPath,
-            from: path.dirname(reflectionEntryPointPath)) {
+        importUris = newEntryPointPaths.map((p) =>
+            path.relative(p, from: path.dirname(reflectionEntryPointPath))) {
     if (this.prefix.isEmpty) throw new ArgumentError.value('(empty)', 'prefix');
   }
 
@@ -43,7 +43,10 @@ class Codegen {
   /// The code generated here should follow the example of code generated for
   /// an [ImportDirective] node.
   String codegenImport() {
-    return 'import \'${importUri}\' as ${prefix};';
+    var count = 0;
+    return importUris
+        .map((importUri) => 'import \'${importUri}\' as ${prefix}${count++};')
+        .join('');
   }
 
   /// Generates code to call the method which sets up Angular2 reflection
@@ -63,7 +66,11 @@ class Codegen {
       reflectorExpression = 'reflector';
     }
 
-    return '${prefix}.${SETUP_METHOD_NAME}(${reflectorExpression});';
+    var count = 0;
+    return importUris
+        .map((_) =>
+            '${prefix}${count++}.${SETUP_METHOD_NAME}(${reflectorExpression});')
+        .join('');
   }
 }
 

modules/angular2/src/transform/reflection_remover/remove_reflection_capabilities.dart

@@ -1,21 +1,26 @@
 library angular2.transform.reflection_remover.remove_reflection_capabilities;
 
+import 'dart:async';
 import 'package:analyzer/analyzer.dart';
+import 'package:barback/barback.dart';
+import 'package:angular2/src/transform/common/asset_reader.dart';
 
 import 'codegen.dart';
 import 'rewriter.dart';
 
-/// Finds the call to the Angular2 [ReflectionCapabilities] constructor
-/// in [code] and replaces it with a call to `setupReflection` in
-/// [newEntryPoint].
+/// Finds the call to the Angular2 `ReflectionCapabilities` constructor
+/// in [reflectionEntryPoint] and replaces it with a call to
+/// `setupReflection` in [newEntryPoint].
 ///
-/// [reflectionEntryPointPath] is the path where [code] is defined and is
-/// used to display parsing errors.
-///
-/// This only searches [code] not `part`s, `import`s, `export`s, etc.
-String removeReflectionCapabilities(
-    String code, String reflectionEntryPointPath, String newEntryPointPath) {
-  var codegen = new Codegen(reflectionEntryPointPath, newEntryPointPath);
+/// This only searches the code in [reflectionEntryPoint], not `part`s,
+/// `import`s, `export`s, etc.
+Future<String> removeReflectionCapabilities(AssetReader reader,
+    AssetId reflectionEntryPoint, Iterable<AssetId> newEntryPoints) async {
+  var code = await reader.readAsString(reflectionEntryPoint);
+  var reflectionEntryPointPath = reflectionEntryPoint.path;
+  var newEntryPointPaths = newEntryPoints.map((id) => id.path);
+
+  var codegen = new Codegen(reflectionEntryPointPath, newEntryPointPaths);
   return new Rewriter(code, codegen)
       .rewrite(parseCompilationUnit(code, name: reflectionEntryPointPath));
 }

modules/angular2/src/transform/reflection_remover/transformer.dart

@@ -1,6 +1,7 @@
 library angular2.transform.reflection_remover.transformer;
 
 import 'dart:async';
+import 'package:angular2/src/transform/common/asset_reader.dart';
 import 'package:angular2/src/transform/common/logging.dart' as log;
 import 'package:angular2/src/transform/common/names.dart';
 import 'package:angular2/src/transform/common/options.dart';
@@ -23,21 +24,24 @@ class ReflectionRemover extends Transformer {
   ReflectionRemover(this.options);
 
   @override
-  bool isPrimary(AssetId id) => options.reflectionEntryPoint == id.path;
+  bool isPrimary(AssetId id) => options.reflectionEntryPoints != null &&
+      options.reflectionEntryPoints.contains(id.path);
 
   @override
   Future apply(Transform transform) async {
     log.init(transform);
 
     try {
-      var newEntryPoint = new AssetId(
-              transform.primaryInput.id.package, options.entryPoint)
-          .changeExtension(DEPS_EXTENSION);
+      var newEntryPoints = options.entryPoints.map((entryPoint) {
+        return new AssetId(transform.primaryInput.id.package, entryPoint)
+            .changeExtension(DEPS_EXTENSION);
+      });
+      var reader = new AssetReader.fromTransform(transform);
 
-      var assetCode = await transform.primaryInput.readAsString();
-      transform.addOutput(new Asset.fromString(transform.primaryInput.id,
-          removeReflectionCapabilities(
-              assetCode, transform.primaryInput.id.path, newEntryPoint.path)));
+      var transformedCode = await removeReflectionCapabilities(
+          reader, transform.primaryInput.id, newEntryPoints);
+      transform.addOutput(
+          new Asset.fromString(transform.primaryInput.id, transformedCode));
     } catch (ex, stackTrace) {
       log.logger.error('Removing reflection failed.\n'
           'Exception: $ex\n'