Feature request - filter stacktrace

[Yjuq]

Hey :)

A option to filter the stacktrace would be great. Exceptions are always long and the most informations are not needed. It would be great if I can choose in the tinylog.properties which packages information should be printed with TinyLog.

Something like this:
tinylog.stacktrace.filter = acg|javafx.scene - This could be print only informations about the package acg (and sub packages like acg.* etc.) and all information in the package javafx.scene.*

Maybe a other option with this feature would be nice. To remove the "caused by" information in exceptions (just don't print it):

java.lang.IllegalArgumentException: Invalid URL: Invalid URL or resource not found
        at acg.component.Card.<init>(Card.java:38)
        at acg.Applet.start(Applet.java:17)
< This Informations are not needed: >
    Caused by: java.lang.IllegalArgumentException: Invalid URL or resource not found
        at javafx.scene.image.Image.validateUrl(Image.java:1110)
        at javafx.scene.image.Image.<init>(Image.java:620)
        at acg.component.Card.<init>(Card.java:38)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance0(Native Method)
        at sun.reflect.NativeConstructorAccessorImpl.newInstance(Unknown Source)
        at sun.reflect.DelegatingConstructorAccessorImpl.newInstance(Unknown Source)
        ...

The option for that could be: 'tinylog.stacktrace.cause=true|false' to turn it on or off.

---

Currently I use a extern class to filer the informations with a regex pattern. Maybe it helps you a bit to develop an idea for your project:

public class StackTrace {
	private static String pattern = "^acg\\..*$"; // Filter for acg.* package
	
	// ++++++++++ +++++++++ ++++++++ +++++++ ++++++ +++++ ++++ +++ ++ +
	
	private StackTrace() {
		// Nothing to do
	}
	
	// ++++++++++ +++++++++ ++++++++ +++++++ ++++++ +++++ ++++ +++ ++ +
	
	public static void filter(Exception exception) {
		Stack<StackTraceElement> stack = new Stack<StackTraceElement>();
		StackTraceElement[] ste = exception.getStackTrace();
		
		for (int i = 0; i < ste.length; ++i) {
			if (ste[i].getClassName().matches(pattern)) {
				stack.push(ste[i]);
			}
		}
		
		exception.setStackTrace(stack.toArray(new StackTraceElement[stack.size()]));
	}
}

I can't remove the "caused by" information by myself without changing your sourcecode from your Logger class.

If you need help with this - I could maybe implement this feature by myself and share the source with you. So you can add this to your project.

Nice work by the way. I like your logger :)

[pmwmedia]

I've thought about it and made a first draft that includes your use cases and some of my ideas that I've already thought about once. A stack trace filter should be configurable either globally or for specific writers. To do this, a stack trace filter must not change an existing exception (or other throwable), but return a new one.

interface StackTraceFilter {

	Throwable filter(Throwable ex);

}

Like policies, stack filters should be extendable as META-INF services. In the standard set of tinylog I see the following four stack trace filters:

1. keep: a|b for keeping only stack trace elements with the package a and b and their sub packages.

2. remove: a|b for removing all stack trace elements with the package a and b and their sub packages.

3. discard-cause for removing all cause throwables.

4. compress-cause for removing stack trace elements from a parent throwable which are just repeated from cause throwables like JBoss does it by default. I love this feature when working with JBoss application servers!

These filters should be combinable, like for example (in tinylog 2 properties are not starting anymore with tinylog.):

stacktrace = keep: org.mypackage|com.mypackage, remove: org.mypackage.test
writer1.stacktrace = discard-cause
writer1.stacktrace = compress-cause

Criticism and suggestions for improvement are welcome!

[pmwmedia]

Fixed in branch v2.1

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