Last argument of log message stripped if Throwable, even when cause is given as well #876
Description
If a Throwable type is passed to match the last {} argument, it is ignored, and the formatted log message will write {} instead.
Example:
package com.test; import ch.qos.logback.core.Appender; import org.slf4j.Logger; import org.slf4j.LoggerFactory; import org.slf4j.event.Level; public class Test { static final Logger log = LoggerFactory.getLogger(Test.class); public static void main(String[] args) { log.info("SLF4J Version: {}", Logger.class.getPackage().getImplementationVersion()); log.info("Logback Version: {}", Appender.class.getPackage().getImplementationVersion()); Exception ex = new CustomException("Some message"); log.error("Exception Message: {}", ex, ex); log.makeLoggingEventBuilder(Level.WARN) .setMessage("Exception Message: {}") .addArgument(ex) .setCause(ex) .log(); } static class CustomException extends Exception { public CustomException(String msg) { super(msg); } @Override public String toString() { return "Custom Message"; } } }Expected output:
[main] INFO com.test.Test -- SLF4J Version: 2.0.15 [main] INFO com.test.Test -- Logback Version: 1.5.11 [main] ERROR com.test.Test -- Exception Message: Custom Message com.test.Test$CustomException: Some message at com.test.Test.main(Test.java:15) [main] WARN com.test.Test -- Exception Message: Custom Message com.test.Test$CustomException: Some message at com.test.Test.main(Test.java:15) Actual output:
[main] INFO com.test.Test -- SLF4J Version: 2.0.15 [main] INFO com.test.Test -- Logback Version: 1.5.11 [main] ERROR com.test.Test -- Exception Message: {} com.test.Test$CustomException: Some message at com.test.Test.main(Test.java:15) [main] WARN com.test.Test -- Exception Message: {} com.test.Test$CustomException: Some message at com.test.Test.main(Test.java:15) Workaround:
Explicitly calling .toString() on the argument (log.error("Exception Message: {}", ex.toString(), ex)), or adding a bogus extra "" argument (log.error("Exception Message: {}", ex, "", ex)) works as a work around, but causes static analysis tools, including the one in IntelliJ, to warn about it.