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logger.dart
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logger.dart
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import 'dart:async';
import 'dart:collection';
import 'level.dart';
import 'log_record.dart';
/// Whether to allow fine-grain logging and configuration of loggers in a
/// hierarchy.
///
/// When false, all hierarchical logging instead is merged in the root logger.
bool hierarchicalLoggingEnabled = false;
/// Automatically record stack traces for any message of this level or above.
///
/// Because this is expensive, this is off by default.
Level recordStackTraceAtLevel = Level.OFF;
/// The default [Level].
const defaultLevel = 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?.name.isNotEmpty ?? false ? '${parent!.fullName}.$name' : name;
/// Parent of this logger in the hierarchy of loggers.
final Logger? parent;
/// Logging [Level] used for entries generated on this logger.
///
/// Only the root logger is guaranteed to have a non-null [Level].
Level? _level;
/// Private modifiable map of child loggers, indexed by their simple names.
final Map<String, Logger> _children;
/// Children in the hierarchy of loggers, indexed by their simple names.
///
/// This is an unmodifiable map.
final Map<String, Logger> children;
/// Controller used to notify when log entries are added to this logger.
///
/// If hierarchical logging is disabled then this is `null` for all but the
/// root [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) =>
_loggers.putIfAbsent(name, () => Logger._named(name));
/// Creates a new detached [Logger].
///
/// Returns a new [Logger] instance (unlike `new Logger`, which returns a
/// [Logger] singleton), which doesn't have any parent or children,
/// and is not a part of the global hierarchical loggers structure.
///
/// It can be useful when you just need a local short-living logger,
/// which you'd like to be garbage-collected later.
factory Logger.detached(String name) =>
Logger._internal(name, null, <String, Logger>{});
factory Logger._named(String name) {
if (name.startsWith('.')) {
throw ArgumentError("name shouldn't start with a '.'");
}
// Split hierarchical names (separated with '.').
var dot = name.lastIndexOf('.');
Logger? parent;
String thisName;
if (dot == -1) {
if (name != '') parent = Logger('');
thisName = name;
} else {
parent = Logger(name.substring(0, dot));
thisName = name.substring(dot + 1);
}
return Logger._internal(thisName, parent, <String, Logger>{});
}
Logger._internal(this.name, this.parent, Map<String, Logger> children)
: _children = children,
children = UnmodifiableMapView(children) {
if (parent == null) {
_level = defaultLevel;
} else {
parent!._children[name] = this;
}
}
/// Effective level considering the levels established in this logger's
/// parents (when [hierarchicalLoggingEnabled] is true).
Level get level {
Level effectiveLevel;
if (parent == null) {
// We're either the root logger or a detached logger. Return our own
// level.
effectiveLevel = _level!;
} else if (!hierarchicalLoggingEnabled) {
effectiveLevel = root._level!;
} else {
effectiveLevel = _level ?? parent!.level;
}
// ignore: unnecessary_null_comparison
assert(effectiveLevel != null);
return effectiveLevel;
}
/// Override the level for this particular [Logger] and its children.
///
/// Setting this to `null` makes it inherit the [parent]s level.
set level(Level? value) {
if (!hierarchicalLoggingEnabled && parent != null) {
throw UnsupportedError(
'Please set "hierarchicalLoggingEnabled" to true if you want to '
'change the level on a non-root logger.');
}
if (parent == null && value == null) {
throw UnsupportedError(
'Cannot set the level to `null` on a logger with no parent.');
}
_level = value;
}
/// Returns a stream of messages added to this [Logger].
///
/// You can listen for messages using the standard stream APIs, for instance:
///
/// ```dart
/// logger.onRecord.listen((record) { ... });
/// ```
Stream<LogRecord> get onRecord => _getStream();
void clearListeners() {
if (hierarchicalLoggingEnabled || parent == 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 the object and the result will be logged. The log record will
/// contain a field holding the original object.
///
/// The log record will also contain a field for the zone in which this call
/// was made. This can be advantageous if a log listener wants to handler
/// records of different zones differently (e.g. group log records by HTTP
/// request if each HTTP request handler runs in it's own zone).
void log(Level logLevel, Object? message,
[Object? error, StackTrace? stackTrace, Zone? zone]) {
Object? object;
if (isLoggable(logLevel)) {
if (message is Function) {
message = message();
}
String msg;
if (message is String) {
msg = message;
} else {
msg = message.toString();
object = message;
}
if (stackTrace == null && logLevel >= recordStackTraceAtLevel) {
stackTrace = StackTrace.current;
error ??= 'autogenerated stack trace for $logLevel $msg';
}
zone ??= Zone.current;
var record =
LogRecord(logLevel, msg, fullName, error, stackTrace, zone, object);
if (parent == null) {
_publish(record);
} else if (!hierarchicalLoggingEnabled) {
root._publish(record);
} else {
Logger? target = this;
while (target != null) {
target._publish(record);
target = target.parent;
}
}
}
}
/// Log message at level [Level.FINEST].
///
/// See [log] for information on how non-String [message] arguments are
/// handled.
void finest(Object? message, [Object? error, StackTrace? stackTrace]) =>
log(Level.FINEST, message, error, stackTrace);
/// Log message at level [Level.FINER].
///
/// See [log] for information on how non-String [message] arguments are
/// handled.
void finer(Object? message, [Object? error, StackTrace? stackTrace]) =>
log(Level.FINER, message, error, stackTrace);
/// Log message at level [Level.FINE].
///
/// See [log] for information on how non-String [message] arguments are
/// handled.
void fine(Object? message, [Object? error, StackTrace? stackTrace]) =>
log(Level.FINE, message, error, stackTrace);
/// Log message at level [Level.CONFIG].
///
/// See [log] for information on how non-String [message] arguments are
/// handled.
void config(Object? message, [Object? error, StackTrace? stackTrace]) =>
log(Level.CONFIG, message, error, stackTrace);
/// Log message at level [Level.INFO].
///
/// See [log] for information on how non-String [message] arguments are
/// handled.
void info(Object? message, [Object? error, StackTrace? stackTrace]) =>
log(Level.INFO, message, error, stackTrace);
/// Log message at level [Level.WARNING].
///
/// See [log] for information on how non-String [message] arguments are
/// handled.
void warning(Object? message, [Object? error, StackTrace? stackTrace]) =>
log(Level.WARNING, message, error, stackTrace);
/// Log message at level [Level.SEVERE].
///
/// See [log] for information on how non-String [message] arguments are
/// handled.
void severe(Object? message, [Object? error, StackTrace? stackTrace]) =>
log(Level.SEVERE, message, error, stackTrace);
/// Log message at level [Level.SHOUT].
///
/// See [log] for information on how non-String [message] arguments are
/// handled.
void shout(Object? message, [Object? error, StackTrace? stackTrace]) =>
log(Level.SHOUT, message, error, stackTrace);
Stream<LogRecord> _getStream() {
if (hierarchicalLoggingEnabled || parent == null) {
return (_controller ??= StreamController<LogRecord>.broadcast(sync: true))
.stream;
} else {
return root._getStream();
}
}
void _publish(LogRecord record) => _controller?.add(record);
/// Top-level root [Logger].
static final Logger root = Logger('');
/// All [Logger]s in the system.
static final Map<String, Logger> _loggers = <String, Logger>{};
}