Server options handling.

pkg/analysis_server/lib/src/server_options.dart

Index: pkg/analysis_server/lib/src/server_options.dart
diff --git a/pkg/analysis_server/lib/src/server_options.dart b/pkg/analysis_server/lib/src/server_options.dart
new file mode 100644
index 0000000000000000000000000000000000000000..4a59efb196f41cfa65b2b939d705d16fe1deb043
--- /dev/null
+++ b/pkg/analysis_server/lib/src/server_options.dart
@@ -0,0 +1,110 @@
+// 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 analysis_server.src.server_options;
+
+import 'dart:collection';
+import 'dart:io';
+
+import 'package:path/path.dart' as path;
+import 'package:yaml/yaml.dart';
+
+const _optionsFileName = 'dart_analysis_server.options';
+
+/// The shared options instance.
+ServerOptions _serverOptions;
+
+/// Server options.
+ServerOptions get serverOptions {
+  if (_serverOptions == null) {
+    _serverOptions = _loadOptions();
+  }
+  return _serverOptions;
+}
+
+/// Find the options file relative to the user's home directory.
+/// Returns `null` if there is none or the user's homedir cannot
+/// be derived from the platform's environment (e.g., `HOME` and
+/// `UserProfile` for mac/Linux and Windows respectively).
+File _findOptionsFile() {
+  String home;
+  Map<String, String> envVars = Platform.environment;
+  if (Platform.isMacOS || Platform.isLinux) {
+    home = envVars['HOME'];
+  } else if (Platform.isWindows) {
+    home = envVars['UserProfile'];
+  }
+
+  if (home == null) {
+    return null;
+  }
+
+  return new File(path.context.join(home, _optionsFileName));
+}
+
+ServerOptions _loadOptions() {
+  File optionsFile = _findOptionsFile();
+  try {
+    if (optionsFile != null && optionsFile.existsSync()) {
+      return new ServerOptions.fromFile(optionsFile);
+    }
+  } catch (e) {
+    // Fall through.
+  }
+  return new ServerOptions._empty();
+}
+
+/// Describes options captured in an external options file.
+/// `ServerOptions` are described in a file `dart_analysis_server.options`
+/// located in the user's home directory. Options are defined in YAML and
+/// read once and cached. In order for changes to be picked up, server needs
+/// to be restarted.
+class ServerOptions {
+  final Map<String, dynamic> _options = new HashMap<String, dynamic>();
+
+  /// Load options from the given [contents].
+  ServerOptions.fromContents(String contents) {
+    _readOptions(contents);
+  }
+
+  /// Load options from the given [options] file.
+  factory ServerOptions.fromFile(File options) =>
+      new ServerOptions.fromContents(options.readAsStringSync());
+
+  /// Create an empty options object.
+  ServerOptions._empty();
+
+  /// Get the value for `key` from the options file.
+  dynamic operator [](String key) => _options[key];
+
+  /// Get a String value for this `key` or [defaultValue] if undefined
+  /// or not a String.
+  String getStringValue(String key, {String defaultValue: null}) {
+    var value = _options[key];
+    if (value is String) {
+      return value;
+    }
+    return defaultValue;
+  }
+
+  /// Test whether the given [booleanPropertyKey] is set to the value `true`.
+  /// For example:
+  ///     myDebugOption1:true
+  ///     myDebugOption2:TRUE # Also true (case and trailing whitespace are ignored).
+  ///     myDebugOption3:false
+  ///     myDebugOption4:off  # Treated as `false`.
+  ///     myDebugOption5:on   # Also read as `false`.
+  bool isSet(String booleanPropertyKey) => _options[booleanPropertyKey] == true;
+
+  void _readOptions(String contents) {
+    var doc = loadYaml(contents);
+    if (doc is YamlMap) {
+      doc.forEach((k, v) {
+        if (k is String) {
+          _options[k] = v;
+        }
+      });
+    }
+  }
+}