Add observatory_pub_packages snapshot to third_party

observatory_pub_packages/logging/logging.dart

+// Copyright (c) 2012, 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 logging;
+
+import 'dart:async';
+import 'dart:collection';
+
+/**
+ * Whether to allow fine-grain logging and configuration of loggers in a
+ * hierarchy. When false, all logging is merged in the root logger.
+ */
+bool hierarchicalLoggingEnabled = false;
+
+/**
+ * Level for the root-logger. This will be the level of all loggers if
+ * [hierarchicalLoggingEnabled] is false.
+ */
+Level _rootLevel = Level.INFO;
+
+
+/**
+ * Use a [Logger] to log debug messages. [Logger]s are named using a
+ * hierarchical dot-separated name convention.
+ */
+class Logger {
+  /** Simple name of this logger. */
+  final String name;
+
+  /** The full name of this logger, which includes the parent's full name. */
+  String get fullName =>
+      (parent == null || parent.name == '') ? name : '${parent.fullName}.$name';
+
+  /** Parent of this logger in the hierarchy of loggers. */
+  final Logger parent;
+
+  /** Logging [Level] used for entries generated on this logger. */
+  Level _level;
+
+  final Map<String, Logger> _children;
+
+  /** Children in the hierarchy of loggers, indexed by their simple names. */
+  final Map<String, Logger> children;
+
+  /** Controller used to notify when log entries are added to this logger. */
+  StreamController<LogRecord> _controller;
+
+  /**
+   * Singleton constructor. Calling `new Logger(name)` will return the same
+   * actual instance whenever it is called with the same string name.
+   */
+  factory Logger(String name) {
+    return _loggers.putIfAbsent(name, () => new Logger._named(name));
+  }
+
+  factory Logger._named(String name) {
+    if (name.startsWith('.')) {
+      throw new ArgumentError("name shouldn't start with a '.'");
+    }
+    // Split hierarchical names (separated with '.').
+    int dot = name.lastIndexOf('.');
+    Logger parent = null;
+    String thisName;
+    if (dot == -1) {
+      if (name != '') parent = new Logger('');
+      thisName = name;
+    } else {
+      parent = new Logger(name.substring(0, dot));
+      thisName = name.substring(dot + 1);
+    }
+    return new Logger._internal(thisName, parent, new Map<String, Logger>());
+  }
+
+  Logger._internal(this.name, this.parent, Map<String, Logger> children) :
+    this._children = children,
+    this.children = new UnmodifiableMapView(children) {
+    if (parent != null) parent._children[name] = this;
+  }
+
+  /**
+   * Effective level considering the levels established in this logger's parents
+   * (when [hierarchicalLoggingEnabled] is true).
+   */
+  Level get level {
+    if (hierarchicalLoggingEnabled) {
+      if (_level != null) return _level;
+      if (parent != null) return parent.level;
+    }
+    return _rootLevel;
+  }
+
+  /** Override the level for this particular [Logger] and its children. */
+  void set level(Level value) {
+    if (hierarchicalLoggingEnabled && parent != null) {
+      _level = value;
+    } else {
+      if (parent != null) {
+        throw new UnsupportedError(
+            'Please set "hierarchicalLoggingEnabled" to true if you want to '
+            'change the level on a non-root logger.');
+      }
+      _rootLevel = value;
+    }
+  }
+
+  /**
+   * Returns an stream of messages added to this [Logger]. You can listen for
+   * messages using the standard stream APIs, for instance:
+   *    logger.onRecord.listen((record) { ... });
+   */
+  Stream<LogRecord> get onRecord => _getStream();
+
+  void clearListeners() {
+    if (hierarchicalLoggingEnabled || parent == null) {
+      if (_controller != null) {
+        _controller.close();
+        _controller = null;
+      }
+    } else {
+      root.clearListeners();
+    }
+  }
+
+  /** Whether a message for [value]'s level is loggable in this logger. */
+  bool isLoggable(Level value) => (value >= level);
+
+  /**
+   * Adds a log record for a [message] at a particular [logLevel] if
+   * `isLoggable(logLevel)` is true.
+   *
+   * Use this method to create log entries for user-defined levels. To record a
+   * message at a predefined level (e.g. [Level.INFO], [Level.WARNING], etc) you
+   * can use their specialized methods instead (e.g. [info], [warning], etc).
+   *
+   * If [message] is a [Function], it will be lazy evaluated. Additionally, if
+   * [message] or its evaluated value is not a [String], then 'toString()' will
+   * be called on it and the result will be logged.
+   */
+  void log(Level logLevel, message, [Object error, StackTrace stackTrace]) {
+    if (isLoggable(logLevel)) {
+      // If message is a Function, evaluate it.
+      if (message is Function) message = message();
+      // If message is still not a String, call toString().
+      if (message is! String) message = message.toString();
+
+      var record = new LogRecord(logLevel, message, fullName, error,
+          stackTrace);
+
+      if (hierarchicalLoggingEnabled) {
+        var target = this;
+        while (target != null) {
+          target._publish(record);
+          target = target.parent;
+        }
+      } else {
+        root._publish(record);
+      }
+    }
+  }
+
+  /** Log message at level [Level.FINEST]. */
+  void finest(message, [Object error, StackTrace stackTrace]) =>
+      log(Level.FINEST, message, error, stackTrace);
+
+  /** Log message at level [Level.FINER]. */
+  void finer(message, [Object error, StackTrace stackTrace]) =>
+      log(Level.FINER, message, error, stackTrace);
+
+  /** Log message at level [Level.FINE]. */
+  void fine(message, [Object error, StackTrace stackTrace]) =>
+      log(Level.FINE, message, error, stackTrace);
+
+  /** Log message at level [Level.CONFIG]. */
+  void config(message, [Object error, StackTrace stackTrace]) =>
+      log(Level.CONFIG, message, error, stackTrace);
+
+  /** Log message at level [Level.INFO]. */
+  void info(message, [Object error, StackTrace stackTrace]) =>
+      log(Level.INFO, message, error, stackTrace);
+
+  /** Log message at level [Level.WARNING]. */
+  void warning(message, [Object error, StackTrace stackTrace]) =>
+      log(Level.WARNING, message, error, stackTrace);
+
+  /** Log message at level [Level.SEVERE]. */
+  void severe(message, [Object error, StackTrace stackTrace]) =>
+      log(Level.SEVERE, message, error, stackTrace);
+
+  /** Log message at level [Level.SHOUT]. */
+  void shout(message, [Object error, StackTrace stackTrace]) =>
+      log(Level.SHOUT, message, error, stackTrace);
+
+  Stream<LogRecord> _getStream() {
+    if (hierarchicalLoggingEnabled || parent == null) {
+      if (_controller == null) {
+        _controller = new StreamController<LogRecord>.broadcast(sync: true);
+      }
+      return _controller.stream;
+    } else {
+      return root._getStream();
+    }
+  }
+
+  void _publish(LogRecord record) {
+    if (_controller != null) {
+      _controller.add(record);
+    }
+  }
+
+  /** Top-level root [Logger]. */
+  static Logger get root => new Logger('');
+
+  /** All [Logger]s in the system. */
+  static final Map<String, Logger> _loggers = <String, Logger>{};
+}
+
+
+/** Handler callback to process log entries as they are added to a [Logger]. */
+typedef void LoggerHandler(LogRecord);
+
+/**
+ * [Level]s to control logging output. Logging can be enabled to include all
+ * levels above certain [Level]. [Level]s are ordered using an integer
+ * value [Level.value]. The predefined [Level] constants below are sorted as
+ * follows (in descending order): [Level.SHOUT], [Level.SEVERE],
+ * [Level.WARNING], [Level.INFO], [Level.CONFIG], [Level.FINE], [Level.FINER],
+ * [Level.FINEST], and [Level.ALL].
+ *
+ * We recommend using one of the predefined logging levels. If you define your
+ * own level, make sure you use a value between those used in [Level.ALL] and
+ * [Level.OFF].
+ */
+class Level implements Comparable<Level> {
+
+  final String name;
+
+  /**
+   * Unique value for this level. Used to order levels, so filtering can exclude
+   * messages whose level is under certain value.
+   */
+  final int value;
+
+  const Level(this.name, this.value);
+
+  /** Special key to turn on logging for all levels ([value] = 0). */
+  static const Level ALL = const Level('ALL', 0);
+
+  /** Special key to turn off all logging ([value] = 2000). */
+  static const Level OFF = const Level('OFF', 2000);
+
+  /** Key for highly detailed tracing ([value] = 300). */
+  static const Level FINEST = const Level('FINEST', 300);
+
+  /** Key for fairly detailed tracing ([value] = 400). */
+  static const Level FINER = const Level('FINER', 400);
+
+  /** Key for tracing information ([value] = 500). */
+  static const Level FINE = const Level('FINE', 500);
+
+  /** Key for static configuration messages ([value] = 700). */
+  static const Level CONFIG = const Level('CONFIG', 700);
+
+  /** Key for informational messages ([value] = 800). */
+  static const Level INFO = const Level('INFO', 800);
+
+  /** Key for potential problems ([value] = 900). */
+  static const Level WARNING = const Level('WARNING', 900);
+
+  /** Key for serious failures ([value] = 1000). */
+  static const Level SEVERE = const Level('SEVERE', 1000);
+
+  /** Key for extra debugging loudness ([value] = 1200). */
+  static const Level SHOUT = const Level('SHOUT', 1200);
+
+  static const List<Level> LEVELS = const
+      [ALL, FINEST, FINER, FINE, CONFIG, INFO, WARNING, SEVERE, SHOUT, OFF];
+
+  bool operator ==(Object other) => other is Level && value == other.value;
+  bool operator <(Level other) => value < other.value;
+  bool operator <=(Level other) => value <= other.value;
+  bool operator >(Level other) => value > other.value;
+  bool operator >=(Level other) => value >= other.value;
+  int compareTo(Level other) => value - other.value;
+  int get hashCode => value;
+  String toString() => name;
+}
+
+
+/**
+ * A log entry representation used to propagate information from [Logger] to
+ * individual [Handler]s.
+ */
+class LogRecord {
+  final Level level;
+  final String message;
+
+  /** Logger where this record is stored. */
+  final String loggerName;
+
+  /** Time when this record was created. */
+  final DateTime time;
+
+  /** Unique sequence number greater than all log records created before it. */
+  final int sequenceNumber;
+
+  static int _nextNumber = 0;
+
+  /** Associated error (if any) when recording errors messages. */
+  final Object error;
+
+  /** Associated stackTrace (if any) when recording errors messages. */
+  final StackTrace stackTrace;
+
+  LogRecord(this.level, this.message, this.loggerName, [this.error,
+                                                        this.stackTrace])
+      : time = new DateTime.now(),
+        sequenceNumber = LogRecord._nextNumber++;
+
+  String toString() => '[${level.name}] $loggerName: $message';
+}