Provide a programmatic way to configure Picocli's TraceLevel

[ekinano]

The current pattern is to set the picocli.trace system property. It would be nice if there were a more programmatic way to do this, e.g. something like

cmdLine.setTraceLevel(OFF)

For context, we are currently using Picocli's parsing capabilities in an environment where a pattern like System.setProperty is heavily discouraged and requires a security exception.

[remkop]

Hi @ekinano, thanks for raising this.

One could call System.setProperty in the main method before doing anything else to accomplish this programmatically, or am I missing something?

[ekinano]

Thanks for the quick reply @remkop. System.setProperty works, but it is a highly discouraged practice at my company to the point where you need a security exception to be able to use it. While we can probably get that exception for our use-case, it seems better for us to avoid that conversation entirely if there can be another way of setting the trace level without using System.setProperty. It would be nice if that way would be through the Picocli objects directly like e.g. CommandLine. Hopefully that makes sense?

(If you're curious, we have a server for processing CLI-like arguments. We are leveraging Picocli's annotations to specify our "command" classes and its parser to parse those subcommands from the request. We would like to turn off Picocli's tracing to avoid filling our logs).

[remkop]

@ekinano Thank you for the clarification. That makes sense.

Will you be able to provide a pull request for this?

[remkop]

This has been implemented and will be included in the 4.7.0 release.
Thank you for the suggestion!

Details

(from the release notes):

From picocli 4.7.0, applications can programmatically set the trace level, and use tracing in custom components.

In addition to setting system property picocli.trace, applications can now change the trace level via the Tracer::setLevel method. For example:

CommandLine.tracer().setLevel(CommandLine.TraceLevel.INFO);

The new public method CommandLine.tracer() returns the singleton Tracer object that is used internally by picocli, and can also be used by custom component implementations to do tracing. For example:

class MyIntConverter implements ITypeConverter<Integer> {
    public Integer convert(String value) {
        try {
            return Integer.parseInt(value);
        } catch (NumberFormatException ex) {
            CommandLine.tracer().info(
                    "Could not convert %s to Integer, returning default value -1", value);
            return -1;
        }
    }
}