I have been trying to convert our logging configuration to the groovy based configuration and have run into an issue with setting the SizeAndTimeBasedFNATP up. I used the converter tool to convert our configuration and have also tried the examples in the documentation:

import ch.qos.logback.classic.encoder.PatternLayoutEncoder
import ch.qos.logback.core.rolling.RollingFileAppender
import ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP
import ch.qos.logback.core.rolling.TimeBasedRollingPolicy

import static ch.qos.logback.classic.Level.DEBUG

appender("ROLLING", RollingFileAppender) {
file = "mylog.txt"
rollingPolicy(TimeBasedRollingPolicy) {
fileNamePattern = "mylog-%d

{yyyy-MM-dd}

.%i.txt"
timeBasedFileNamingAndTriggeringPolicy(SizeAndTimeBasedFNATP)

{ maxFileSize = "100MB" }

}
encoder(PatternLayoutEncoder)

{ pattern = "%msg%n" }

}
root(DEBUG, ["ROLLING"])

Everything I've tried has resulted in this exception:
java.lang.NullPointerException at ch.qos.logback.core.rolling.TimeBasedFileNamingAndTriggeringPolicyBase.start(TimeBasedFileNamingAndTriggeringPolicyBase.java:46) at
ch.qos.logback.core.rolling.SizeAndTimeBasedFNATP.start(SizeAndTimeBasedFNATP.java:36)
...

If I step through the configuration process it appears that on line 46 in TimeBasedFileNamingAndTriggeringPolicyBase the tbrp member variable is null here.