Roll Observatory packages and add a roll script

code_transformers/lib/src/entry_point.dart

-// Copyright (c) 2014, 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 'dart:async';
-
-import 'package:analyzer/analyzer.dart' as analyzer;
-import 'package:analyzer/src/generated/ast.dart';
-import 'package:barback/barback.dart';
-
-/// Checks to see if the provided AssetId is a Dart file in a directory which
-/// may contain entry points.
-///
-/// Directories are considered entry points if they are Dart files located in
-/// web/, test/, benchmark/ or example/.
-bool isPossibleDartEntryId(AssetId id) {
-  if (id.extension != '.dart') return false;
-
-  return [
-    'benchmark',
-    'example',
-    'test',
-    'web'
-  ].any((dir) => id.path.startsWith("$dir/"));
-}
-
-/// Checks to see if the provided Asset is possibly a Dart entry point.
-///
-/// Assets are considered entry points if they pass [isPossibleDartEntryId] and
-/// have a main() method.
-///
-/// Because this only analyzes the primary asset this may return true for files
-/// which are not dart entries if the file does not have a main() but does have
-/// parts or exports.
-Future<bool> isPossibleDartEntry(Asset asset) {
-  if (!isPossibleDartEntryId(asset.id)) return new Future.value(false);
-
-  return asset.readAsString().then((contents) {
-    return _couldBeEntrypoint(
-        analyzer.parseCompilationUnit(contents, suppressErrors: true));
-  });
-}
-
-bool _couldBeEntrypoint(CompilationUnit compilationUnit) {
-  // Allow two or fewer arguments so that entrypoints intended for use with
-  // [spawnUri] get counted.
-  var hasMain = compilationUnit.declarations.any(
-      (node) => node is FunctionDeclaration &&
-          node.name.name == "main" &&
-          node.functionExpression.parameters.parameters.length <= 2);
-
-  if (hasMain) return true;
-
-  // If it has an export or a part, assume the worst- that the main could be
-  // in there.
-  // We avoid loading those since this can be run from isPrimaryAsset calls
-  // where we do not have access to other sources.
-  return compilationUnit.directives
-      .any((node) => node is ExportDirective || node is PartDirective);
-}