davianspace_logging 1.0.3

Logging framework for Dart and Flutter inspired by Microsoft.Extensions.Logging with providers, filtering, scopes, structured logs, and JSON output.

davianspace_logging

Enterprise-grade structured logging framework for Dart and Flutter. Conceptually equivalent to Microsoft.Extensions.Logging, expressed idiomatically in Dart.

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Features

Capability	Description
Structured logging	Properties stored separately from messages; providers decide formatting
Multiple providers	Console, debug, memory, and custom providers run simultaneously
Log-level filtering	Global floor, category-prefix rules, and provider-specific rules
Scoped contexts	Zone-aware async-safe scopes automatically inject contextual properties
Logger factory	Category-based logger creation with lifetime management
Pluggable formatters	Simple text and JSON out of the box; implement LogFormatter for custom
Zero allocations	Fast-path exits before allocating when log level is disabled
No dependencies	Pure Dart; works on all platforms (CLI, Flutter, server)

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Quick start

import 'package:davianspace_logging/davianspace_logging.dart';

void main() {
  final factory = LoggingBuilder()
    .addConsole()
    .setMinimumLevel(LogLevel.info)
    .build();

  final logger = factory.createLogger('MyApp');

  logger.info('Application started');
  logger.info('User logged in', properties: {'userId': 42, 'role': 'admin'});
  logger.warning('Disk space low', properties: {'freeGb': 1.2});
  logger.error('Unexpected failure', error: exception, stackTrace: st);

  factory.dispose();
}

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Architecture

LoggingBuilder
    │
    ▼
LoggerFactory (LoggerFactoryImpl)
    ├── FilterRuleSet         ← routing decisions
    ├── TimestampProvider     ← injectable clock
    └── List<LoggerProvider>
            ├── ConsoleLoggerProvider ── ConsoleLogger (stdout + ANSI color)
            ├── DebugLoggerProvider   ── DebugLogger   (dart:developer)
            └── MemoryLoggerProvider  ── MemoryLogger  (in-memory store)

LoggerFactory.createLogger("Category")
    └── LoggerImpl  ←── active LoggingScope (Zone-propagated)
            │
            ▼
          LogEvent (immutable, shared across providers)
            ├── level, category, message, timestamp
            ├── properties     ← caller-supplied structured data
            └── scopeProperties ← merged from LoggingScope chain

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Log levels

enum LogLevel { trace, debug, info, warning, error, critical, none }

Levels are ordered; none suppresses all output:

logger.isEnabled(LogLevel.debug);   // true / false depending on config

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Structured properties

Properties are kept separate from the message so every provider can decide whether to render them inline (text) or persist them as structured fields (JSON):

logger.info(
  'Order placed',
  properties: {
    'orderId': 1042,
    'amount':  299.99,
    'currency': 'USD',
  },
);

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Log filtering

final factory = LoggingBuilder()
  .addConsole()
  .setMinimumLevel(LogLevel.debug)                // global floor
  .addFilterRule(FilterRule(
      categoryPrefix: 'network',
      minimumLevel:   LogLevel.error,             // noisy subsystem override
  ))
  .addFilterRule(FilterRule(
      providerType:   ConsoleLoggerProvider,
      categoryPrefix: 'metrics',
      minimumLevel:   LogLevel.none,              // silence metrics on console
  ))
  .build();

Rule specificity (highest wins):

1. Provider type and category prefix
2. Category prefix only
3. Provider type only
4. Global minimum (catch-all)

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Scoped logging

Scopes carry contextual properties through an entire async call chain via Dart's Zone mechanism — no manual threading required:

final scope = logger.beginScope({
  'requestId': request.id,
  'userId':    request.userId,
});

await scope.runAsync(() async {
  logger.info('Processing');          // ← includes requestId + userId
  await callDownstream();
  logger.info('Done');                // ← still includes requestId + userId
});

Scopes nest; child properties override parent properties with the same key.

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Formatters

Simple (default)

2026-02-25T14:23:01.123456Z [INFO ] OrderService » Order placed  {orderId: 1042}

JSON

{"timestamp":"2026-02-25T14:23:01.123456Z","level":"info","category":"OrderService","message":"Order placed","properties":{"orderId":1042}}

Register a formatter on any provider:

LoggingBuilder()
  .addConsole(formatter: JsonFormatter())
  .build();

Custom formatters implement LogFormatter:

final class MyFormatter implements LogFormatter {
  @override
  String format(LogEvent event) =>
      '[${event.level.label}] ${event.message}';
}

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Custom providers

final class SyslogProvider implements LoggerProvider {
  @override
  Logger createLogger(String category) =>
      SyslogLogger(category: category);

  @override
  void dispose() { /* close socket */ }
}

// Register:
LoggingBuilder().addProvider(SyslogProvider()).build();

Implement EventLogger (extends Logger) to receive a pre-built LogEvent including scope-merged properties:

final class SyslogLogger implements EventLogger {
  @override
  void write(LogEvent event) => syslog(event.level.label, event.message);
  // …
}

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Testing

Use MemoryLoggerProvider + MemoryLogStore to assert log output in unit tests:

test('logs order placed at info level', () {
  final store = MemoryLogStore();
  final factory = LoggingBuilder()
      .addMemory(store: store)
      .setMinimumLevel(LogLevel.trace)
      .build();

  OrderService(factory.createLogger('OrderService'))
      .placeOrder(Order(1, 99.99));

  final event = store.events.single;
  expect(event.level, equals(LogLevel.info));
  expect(event.properties['orderId'], equals(1));
  factory.dispose();
});

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Performance

• Zero allocations when a log level is disabled — isEnabled check exits before any object is created.
• Single LogEvent allocation per log() call, shared across all providers.
• Zone-local scope lookup — O(1) read, no contention.
• No reflection — category names are plain strings; no dart:mirrors.
• Lazy initialisation — provider caches are populated on first access.

Use the isEnabled guard for expensive message construction:

if (logger.isEnabled(LogLevel.debug)) {
  logger.debug('Snapshot: ${expensiveDump()}');
}

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Migration from Microsoft.Extensions.Logging

MEL (C#)	davianspace_logging (Dart)
ILogger	Logger (abstract interface)
ILoggerFactory	LoggerFactory (abstract interface)
ILoggerProvider	LoggerProvider (abstract interface)
ILoggingBuilder	LoggingBuilder (concrete builder)
LogLevel enum	LogLevel enum (same names, lowercase)
ILogger.BeginScope(state)	logger.beginScope(properties)
ILoggerFactory.CreateLogger<T>()	factory.createLogger('TypeName')
using var scope = …	await scope.runAsync(() async { … })
AddConsole()	.addConsole() on LoggingBuilder
Structured logging templates	Plain message + properties map
IDisposable	dispose() method on factory and providers

Key differences

• Dart has no IDisposable / using; use scope.run(...) / scope.runAsync(...) instead of relying on disposal for scope lifetime.
• Structured properties use a Map<String, Object?> instead of C# message templates.
• No dependency injection container required — LoggingBuilder covers DI composition.
• Providers register extensions on LoggingBuilder rather than via IServiceCollection.

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License

MIT © 2026 Davian Space