How to print() to logs in the release mode in Flutter?

Question

My web app has a problem that only manifests in profile and release builds (a widget is not rendering properly, producing only gray). I want to add some print() statements to help figure out what the problem is, but print() doesn't log anything to VSCode debug output window in profile/release builds.

Any ideas how to fix that?

What other techniques can I use to diagnose release-only problems?

Thx

Solution

There are several ways of doing it:

1. Use the following command

   flutter logs
   

2. Use logger package.

   The default implementation (DevelopmentFilter) shows all logs with level >= Logger.level while in debug mode. In release mode all logs are omitted.

   In order to show all logs even in release mode, create your own LogFilter like this:

   class MyFilter extends LogFilter {
     @override
     bool shouldLog(LogEvent event) {
       return true;
     }
   }
   

   Usage:

   void foo() {
     var logger = Logger(filter: MyFilter());
     logger.d('message');
   }
   

3. Use print statement (not sure if this works on web)