Added DateTimeFormatter to PrettyPrinter, closes #80

README.md

@@ -84,7 +84,8 @@ var logger = Logger(
       lineLength: 120, // Width of the output
       colors: true, // Colorful log messages
       printEmojis: true, // Print an emoji for each log message
-      printTime: false // Should each log print contain a timestamp
+      // Should each log print contain a timestamp
+      dateTimeFormat: DateTimeFormat.onlyTimeAndSinceStart,
   ),
 );
 ```

lib/src/date_time_format.dart

@@ -0,0 +1,70 @@
+import 'printers/pretty_printer.dart';
+
+typedef DateTimeFormatter = String Function(DateTime time);
+
+class DateTimeFormat {
+  /// Omits the date and time completely.
+  static const DateTimeFormatter none = _none;
+
+  /// Prints only the time.
+  ///
+  /// Example:
+  /// * `12:30:40.550`
+  static const DateTimeFormatter onlyTime = _onlyTime;
+
+  /// Prints only the time including the difference since [PrettyPrinter.startTime].
+  ///
+  /// Example:
+  /// * `12:30:40.550 (+0:00:00.060700)`
+  static const DateTimeFormatter onlyTimeAndSinceStart = _onlyTimeAndSinceStart;
+
+  /// Prints only the date.
+  ///
+  /// Example:
+  /// * `2019-06-04`
+  static const DateTimeFormatter onlyDate = _onlyDate;
+
+  /// Prints date and time (combines [onlyDate] and [onlyTime]).
+  ///
+  /// Example:
+  /// * `2019-06-04 12:30:40.550`
+  static const DateTimeFormatter dateAndTime = _dateAndTime;
+
+  DateTimeFormat._();
+
+  static String _none(DateTime t) => throw UnimplementedError();
+
+  static String _onlyTime(DateTime t) {
+    String threeDigits(int n) {
+      if (n >= 100) return '$n';
+      if (n >= 10) return '0$n';
+      return '00$n';
+    }
+
+    String twoDigits(int n) {
+      if (n >= 10) return '$n';
+      return '0$n';
+    }
+
+    var now = t;
+    var h = twoDigits(now.hour);
+    var min = twoDigits(now.minute);
+    var sec = twoDigits(now.second);
+    var ms = threeDigits(now.millisecond);
+    return '$h:$min:$sec.$ms';
+  }
+
+  static String _onlyTimeAndSinceStart(DateTime t) {
+    var timeSinceStart = t.difference(PrettyPrinter.startTime!).toString();
+    return '${onlyTime(t)} (+$timeSinceStart)';
+  }
+
+  static String _onlyDate(DateTime t) {
+    String isoDate = t.toIso8601String();
+    return isoDate.substring(0, isoDate.indexOf("T"));
+  }
+
+  static String _dateAndTime(DateTime t) {
+    return "${_onlyDate(t)} ${_onlyTime(t)}";
+  }
+}

lib/src/printers/pretty_printer.dart

@@ -2,6 +2,7 @@ import 'dart:convert';
 import 'dart:math';
 
 import '../ansi_color.dart';
+import '../date_time_format.dart';
 import '../log_event.dart';
 import '../log_level.dart';
 import '../log_printer.dart';
@@ -64,7 +65,7 @@ class PrettyPrinter extends LogPrinter {
   static final _browserStackTraceRegex =
       RegExp(r'^(?:package:)?(dart:\S+|\S+)');
 
-  static DateTime? _startTime;
+  static DateTime? startTime;
 
   /// The index at which the stack trace should start.
   ///
@@ -113,7 +114,11 @@ class PrettyPrinter extends LogPrinter {
   final bool printEmojis;
 
   /// Whether [LogEvent.time] is printed.
-  final bool printTime;
+  @Deprecated("Use `dateTimeFormat` instead.")
+  bool get printTime => dateTimeFormat != DateTimeFormat.none;
+
+  /// Controls the format of [LogEvent.time].
+  final DateTimeFormatter dateTimeFormat;
 
   /// Controls the ascii 'boxing' of different [Level]s.
   ///
@@ -191,14 +196,25 @@ class PrettyPrinter extends LogPrinter {
     this.lineLength = 120,
     this.colors = true,
     this.printEmojis = true,
-    this.printTime = false,
+    @Deprecated(
+        "Use `dateTimeFormat` with `DateTimeFormat.onlyTimeAndSinceStart` or `DateTimeFormat.none` instead.")
+    bool? printTime,
+    DateTimeFormatter dateTimeFormat = DateTimeFormat.none,
     this.excludeBox = const {},
     this.noBoxingByDefault = false,
     this.excludePaths = const [],
     this.levelColors,
     this.levelEmojis,
-  }) {
-    _startTime ??= DateTime.now();
+  })  : assert(
+            (printTime != null && dateTimeFormat == DateTimeFormat.none) ||
+                printTime == null,
+            "Don't set printTime when using dateTimeFormat"),
+        dateTimeFormat = printTime == null
+            ? dateTimeFormat
+            : (printTime
+                ? DateTimeFormat.onlyTimeAndSinceStart
+                : DateTimeFormat.none) {
+    startTime ??= DateTime.now();
 
     var doubleDividerLine = StringBuffer();
     var singleDividerLine = StringBuffer();
@@ -241,6 +257,8 @@ class PrettyPrinter extends LogPrinter {
     var errorStr = event.error?.toString();
 
     String? timeStr;
+    // Keep backwards-compatibility to `printTime` check
+    // ignore: deprecated_member_use_from_same_package
     if (printTime) {
       timeStr = getTime(event.time);
     }
@@ -332,24 +350,7 @@ class PrettyPrinter extends LogPrinter {
   }
 
   String getTime(DateTime time) {
-    String threeDigits(int n) {
-      if (n >= 100) return '$n';
-      if (n >= 10) return '0$n';
-      return '00$n';
-    }
-
-    String twoDigits(int n) {
-      if (n >= 10) return '$n';
-      return '0$n';
-    }
-
-    var now = time;
-    var h = twoDigits(now.hour);
-    var min = twoDigits(now.minute);
-    var sec = twoDigits(now.second);
-    var ms = threeDigits(now.millisecond);
-    var timeSinceStart = now.difference(_startTime!).toString();
-    return '$h:$min:$sec.$ms (+$timeSinceStart)';
+    return dateTimeFormat(time);
   }
 
   // Handles any object that is causing JsonEncoder() problems

lib/web.dart

@@ -2,6 +2,7 @@
 library web;
 
 export 'src/ansi_color.dart';
+export 'src/date_time_format.dart';
 export 'src/filters/development_filter.dart';
 export 'src/filters/production_filter.dart';
 export 'src/log_event.dart';