Logging in Maven 4

[Martin Desruisseaux]

Maven 4 defines a new interface, `org.apache.maven.api.plugin.Log`, with 
the usual debug(…), info(…), warn(…) and error(…) methods in it. Should 
we replace that by `java.lang.System.Logger`? (now possible with Java 
17) The latter is also an interface, so we have the same flexibility for 
customization. The only drawback I could see is that codes such as 
`logger.info("something")` would become 
`logger.log(System.Logger.Level.INFO, "something")`, which is more 
tedious to write. However, this inconvenience may actually be a good 
thing (see below).

We could keep the Maven `Log` interface as a wrapper around 
`System.Logger` for convenience. However, some logging implementations 
such as `java.util.logging` use Java reflection for detecting the caller 
class and method. If we keep the Maven `Log` as a convenience instead of 
direct use of `System.Logger`, I suspect that some logging systems will 
think that all logs always come from `org.apache.maven.api.plugin.Log`. 
This automatic detection is the reason why I propose a complete replacement.

The current logger is used by Maven like below:

   
getLog().info("-------------------------------------------------------------");
   getLog().error("COMPILATION ERROR : ");
   
getLog().info("-------------------------------------------------------------");
   getLog().info(something);
   
getLog().info("-------------------------------------------------------------");

For most logging systems, the above is 5 log records, while actually 
there is only 1 log record and the rest is formatting. The fact that 
System.Logger is more verbose to use may encourage a better pattern like 
below, which results in a single log record:

   getLog().log(System.Logger.Level.ERROR,
            """
            -------------------------------------------------------------
            COMPILATION ERROR :
            -------------------------------------------------------------
            """
            + something +
            """
            -------------------------------------------------------------
            """);

The previous code snippet was mixing info(…) and error(…) maybe for 
coloration. But I see that Maven 4 has a MessageBuilder interface for 
this task, so the log record could be rewritten again like below:

   MessageBuilder mb = messageBuilderFactory.builder()
            
.info("-------------------------------------------------------------").newLine()
            .error("COMPILATION ERROR : ").newLine()
            
.info("-------------------------------------------------------------").newLine()
            .info(something).newLine()
            
.info("-------------------------------------------------------------").newLine();
   getLog().log(System.Logger.Level.ERROR, md.build());

Any opinion?

    Martin