From 815de3404dacbd120a2bf2eb407d62107c5f24b4 Mon Sep 17 00:00:00 2001
From: "jakemac@google.com" <jakemac@google.com>
Date: Fri, 25 Jul 2014 18:35:00 +0000
Subject: [PATCH] updated logging package to accept functions or other
 non-string objects when logging

R=sigmund@google.com

Review URL: https://codereview.chromium.org//420553007

git-svn-id: https://dart.googlecode.com/svn/branches/bleeding_edge/dart/pkg/logging@38584 260f80e4-7a28-3924-810f-c04153c831b5
---
 README.md              |  7 +++++++
 lib/logging.dart       | 28 ++++++++++++++++++----------
 pubspec.yaml           |  2 +-
 test/logging_test.dart | 38 ++++++++++++++++++++++++++++++++++++++
 4 files changed, 64 insertions(+), 11 deletions(-)

diff --git a/README.md b/README.md
index 9d6c978..f4781a7 100644
--- a/README.md
+++ b/README.md
@@ -39,4 +39,11 @@ var future = doSomethingAsync().then((result) {
 }).catchError((e, stackTrace) => log.severe('Oh noes!', e, stackTrace));
 ```
 
+When logging more complex messages, you can pass a closure instead
+that will be evaluated only if the message is actually logged:
+
+```dart
+  log.fine(() => [1, 2, 3, 4, 5].map((e) => e * 4).join("-"));
+```
+
 See the [Logger] class for the different logging methods.
diff --git a/lib/logging.dart b/lib/logging.dart
index d1fb452..5f4bc2b 100644
--- a/lib/logging.dart
+++ b/lib/logging.dart
@@ -134,10 +134,18 @@ class Logger {
    * 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, String message, [Object error,
-                                            StackTrace stackTrace]) {
+  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);
 
@@ -154,35 +162,35 @@ class Logger {
   }
 
   /** Log message at level [Level.FINEST]. */
-  void finest(String message, [Object error, StackTrace stackTrace]) =>
+  void finest(message, [Object error, StackTrace stackTrace]) =>
       log(Level.FINEST, message, error, stackTrace);
 
   /** Log message at level [Level.FINER]. */
-  void finer(String message, [Object error, StackTrace stackTrace]) =>
+  void finer(message, [Object error, StackTrace stackTrace]) =>
       log(Level.FINER, message, error, stackTrace);
 
   /** Log message at level [Level.FINE]. */
-  void fine(String message, [Object error, StackTrace stackTrace]) =>
+  void fine(message, [Object error, StackTrace stackTrace]) =>
       log(Level.FINE, message, error, stackTrace);
 
   /** Log message at level [Level.CONFIG]. */
-  void config(String message, [Object error, StackTrace stackTrace]) =>
+  void config(message, [Object error, StackTrace stackTrace]) =>
       log(Level.CONFIG, message, error, stackTrace);
 
   /** Log message at level [Level.INFO]. */
-  void info(String message, [Object error, StackTrace stackTrace]) =>
+  void info(message, [Object error, StackTrace stackTrace]) =>
       log(Level.INFO, message, error, stackTrace);
 
   /** Log message at level [Level.WARNING]. */
-  void warning(String message, [Object error, StackTrace stackTrace]) =>
+  void warning(message, [Object error, StackTrace stackTrace]) =>
       log(Level.WARNING, message, error, stackTrace);
 
   /** Log message at level [Level.SEVERE]. */
-  void severe(String message, [Object error, StackTrace stackTrace]) =>
+  void severe(message, [Object error, StackTrace stackTrace]) =>
       log(Level.SEVERE, message, error, stackTrace);
 
   /** Log message at level [Level.SHOUT]. */
-  void shout(String message, [Object error, StackTrace stackTrace]) =>
+  void shout(message, [Object error, StackTrace stackTrace]) =>
       log(Level.SHOUT, message, error, stackTrace);
 
   Stream<LogRecord> _getStream() {
diff --git a/pubspec.yaml b/pubspec.yaml
index 678ceef..dd7ba7c 100644
--- a/pubspec.yaml
+++ b/pubspec.yaml
@@ -1,5 +1,5 @@
 name: logging
-version: 0.9.1+2
+version: 0.9.2
 author: Dart Team <misc@dartlang.org>
 description: >
   Provides APIs for debugging and error logging. This library introduces
diff --git a/test/logging_test.dart b/test/logging_test.dart
index 82ef3e1..223498f 100644
--- a/test/logging_test.dart
+++ b/test/logging_test.dart
@@ -418,5 +418,43 @@ main() {
             'WARNING: 9',
             'SHOUT: 10']));
     });
+
+    test('message logging - lazy functions', () {
+      root.level = Level.INFO;
+      var messages = [];
+      root.onRecord.listen((record) {
+        messages.add('${record.level}: ${record.message}');
+      });
+
+      var callCount = 0;
+      var myClosure = () => "${++callCount}";
+
+      root.info(myClosure);
+      root.finer(myClosure);  // Should not get evaluated.
+      root.warning(myClosure);
+
+      expect(messages, equals([
+          'INFO: 1',
+          'WARNING: 2',]));
+    });
+
+    test('message logging - calls toString', () {
+      root.level = Level.INFO;
+      var messages = [];
+      root.onRecord.listen((record) {
+        messages.add('${record.level}: ${record.message}');
+      });
+
+      root.info(5);
+      root.info(false);
+      root.info([1, 2, 3]);
+      root.info(() => 10);
+
+      expect(messages, equals([
+          'INFO: 5',
+          'INFO: false',
+          'INFO: [1, 2, 3]',
+          'INFO: 10',]));
+    });
   });
 }