Move from .sdkext to _sdkext

pkg/analyzer/lib/source/sdk_ext.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 source.sdk_ext;
 
 import 'dart:async';
 import 'dart:collection';
 import 'dart:convert';
 import 'dart:core' hide Resource;
 
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:analyzer/source/package_map_resolver.dart';
 import 'package:analyzer/src/generated/source.dart';
 import 'package:analyzer/src/generated/java_io.dart' show JavaFile;
 import 'package:analyzer/src/generated/source_io.dart' show FileBasedSource;
 import 'package:path/path.dart' as pathos;
 
 /// Given a packageMap (see [PackageMapProvider]), check in each package's lib
-/// directory for the existence of a `.sdkext` file. This file must contain a
+/// directory for the existence of a `_sdkext` file. This file must contain a
 /// JSON encoded map. Each key in the map is a `dart:` library name. Each value
-/// is a path (relative to the directory containing `.sdkext`) to a dart script
+/// is a path (relative to the directory containing `_sdkext`) to a dart script
 /// for the given library. For example:
 /// {
 ///   "dart:sky": "../sdk_ext/dart_sky.dart"
 /// }
 ///
 /// If a key doesn't begin with `dart:` it is ignored.
 class SdkExtUriResolver extends UriResolver {
-  static const String DOT_SDK_EXT_NAME = '.sdkext';
+  static const String SDK_EXT_NAME = '_sdkext';
   static const String DART_COLON_PREFIX = 'dart:';
 
   final Map<String, String> _urlMappings = <String,String>{};
 
   /// Construct a [SdkExtUriResolver] from a package map
   /// (see [PackageMapProvider]).
   SdkExtUriResolver(Map<String, List<Folder>> packageMap) {
     if (packageMap == null) {
       return;
     }
@@ skipping 91 matching lines @@
   /// add any found sdk extensions.
   void _processPackage(String name, List<Folder> libDirs) {
     for (var libDir in libDirs) {
       var sdkExt = _readDotSdkExt(libDir);
       if (sdkExt != null) {
         _processSdkExt(sdkExt, libDir);
       }
     }
   }
 
-  /// Read the contents of [libDir]/[DOT_SDK_EXT_NAME] as a string.
+  /// Read the contents of [libDir]/[SDK_EXT_NAME] as a string.
   /// Returns null if the file doesn't exist.
   String _readDotSdkExt(Folder libDir) {
-    var file = libDir.getChild(DOT_SDK_EXT_NAME);
+    var file = libDir.getChild(SDK_EXT_NAME);
     try {
       return file.readAsStringSync();
     } on FileSystemException catch (e) {
       // File can't be read.
       return null;
     }
   }
 
   /// Given the JSON for an SDK extension ([sdkExtJSON]) and a folder
   /// ([libDir]), setup the uri mapping.
@@ skipping 14 matching lines @@
   void _processSdkExtension(String name, String file, Folder libDir) {
     if (!name.startsWith(DART_COLON_PREFIX)) {
       // SDK extensions must begin with 'dart:'.
       return;
     }
     var key = name;
     var value = libDir.canonicalizePath(file);
     _urlMappings[key] = value;
   }
 }