Simple Logger Logging

simple_logger Logging Guide

simple_logger provides a straightforward, developer-friendly logging API built on top of the standard logging package. It features caller file/line capture (with IDE clickable links), lazy log evaluation, customizable prefixes/emojis, and flexible output formatters.

Guidelines

• Instantiation:
  • SimpleLogger() is implemented as a singleton factory. Calling SimpleLogger() returns the shared global logger instance.
• Level Configuration:
  • Configure the logging level early in application bootstrap (e.g., in main() before runApp()).
  • Use logger.setLevel(...) to set the active threshold (Level.INFO, Level.WARNING, Level.SEVERE, etc.).
• Caller Info Performance:
  • includeCallerInfo: true captures caller stack frame locations, making logs clickable in IDEs. Because stack trace parsing is CPU-intensive, only enable includeCallerInfo in debug mode (kDebugMode or !kReleaseMode).
• Lazy Evaluation:
  • Pass a closure () => 'message' instead of evaluating heavy string interpolation eagerly if the log level might be suppressed.
• Log Routing & Listeners:
  • Use logger.onLogged or custom logger.formatter to forward logs to external error reporting services (e.g. Sentry, Crashlytics) in production.

Examples

1. Basic Bootstrap and Configuration

import 'package:flutter/foundation.dart';
import 'package:simple_logger/simple_logger.dart';

void configureLogger() {
  final logger = SimpleLogger();

  logger.setLevel(
    kReleaseMode ? Level.WARNING : Level.FINEST,
    includeCallerInfo: kDebugMode,
  );

  // Optional: Custom emoji prefixes
  logger.levelPrefixes = {
    Level.INFO: '💡 INFO',
    Level.WARNING: '⚠️ WARNING',
    Level.SEVERE: '🚨 SEVERE',
  };
}

2. Logging Messages and Lazy Evaluation

import 'package:simple_logger/simple_logger.dart';

final logger = SimpleLogger();

void processPayment(String orderId, Map<String, dynamic> rawPayload) {
  // Simple message
  logger.info('Starting payment for order: $orderId');

  // Lazy evaluation (expensive serialization only executed if FINEST is enabled)
  logger.finest(() => 'Order payload: ${rawPayload.toString()}');

  try {
    // Business logic
  } catch (e, stackTrace) {
    logger.severe('Payment failed for $orderId', e, stackTrace);
  }
}

3. Custom Formatter for Production / CI

import 'package:simple_logger/simple_logger.dart';

void setupCiFormatter() {
  final logger = SimpleLogger();

  logger.formatter = (info) {
    final caller = info.callerInfo.isNotEmpty ? ' [${info.callerInfo}]' : '';
    return '[${info.time.toIso8601String()}] [${info.level.name}]$caller: ${info.message}';
  };
}

Common Pitfalls & Anti-Patterns

• ❌ Anti-pattern: Enabling includeCallerInfo: true unconditionally in release builds, causing performance slowdowns.
  • ✔️ Correct: Guard caller info with kDebugMode or assert(...).
• ❌ Anti-pattern: Using standard print() across the codebase alongside SimpleLogger().
  • ✔️ Correct: Route all application logs through SimpleLogger() for consistent level filtering and formatting.