Refactor AnalysisOptionsProvider

pkg/analyzer/lib/source/analysis_options_provider.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.analysis_options_provider;
 
 import 'package:analyzer/file_system/file_system.dart';
 import 'package:yaml/yaml.dart';
 
 /// Provide the options found in the `.analysis_options` file.
 class AnalysisOptionsProvider {
   /// The name of the analysis options source file.
   static const String ANALYSIS_OPTIONS_NAME = '.analysis_options';
 
-  /// Provide the options found in the [ANALYSIS_OPTIONS_NAME] file located in
-  /// [folder]. Return an empty options map if the file does not exist.
+  /// Provide the options found in [root]/[ANALYSIS_OPTIONS_NAME].
+  /// Return an empty options map if the file does not exist.
   Map<String, YamlNode> getOptions(Folder root) {
+    var optionsSource =
+        _readAnalysisOptionsFile(root.getChild(ANALYSIS_OPTIONS_NAME));
+    return getOptionsFromString(optionsSource);
+  }
+
+  /// Provide the options found in [file].
+  /// Return an empty options map if the file does not exist.
+  Map<String, YamlNode> getOptionsFromFile(File file) {
+    var optionsSource = _readAnalysisOptionsFile(file);
+    return getOptionsFromString(optionsSource);
+  }
+
+  /// Provide the options found in [optionsSource].
+  /// Return an empty options map if the source is null.
+  Map<String, YamlNode> getOptionsFromString(String optionsSource) {
     var options = <String, YamlNode>{};
-    var optionsSource = _readAnalysisOptionsFile(root);
     if (optionsSource == null) {
       return options;
     }
     var doc = loadYaml(optionsSource);
     if (doc is! YamlMap) {
       throw new Exception(
           'Bad options file format (expected map, got ${doc.runtimeType})');
     }
     if (doc is YamlMap) {
       doc.forEach((k, v) {
         if (k is! String) {
           throw new Exception(
               'Bad options file format (expected String scope key, '
               'got ${k.runtimeType})');
         }
         options[k] = v;
       });
     }
     return options;
   }
 
-  /// Read the contents of [root]/[ANALYSIS_OPTIONS_NAME] as a string.
+  /// Read the contents of [file] as a string.
   /// Returns null if file does not exist.
-  String _readAnalysisOptionsFile(Folder root) {
-    var file = root.getChild(ANALYSIS_OPTIONS_NAME);
+  String _readAnalysisOptionsFile(File file) {
     try {
       return file.readAsStringSync();
     } on FileSystemException {
       // File can't be read.
       return null;
     }
   }
 }