Log4J pattern layout inconsistencies when locale is specified

[xzel23]

Description

Log4J pattern layout supports a timezone argument and an (undicumented?) locale argument.

These patterns both work as expected, i.e., in the second example the german month names are used even when the system uses an english locale:

•        "%d{dd-MMMM-yyyy}{GMT} %p %m%n",
  

•        "%d{dd-MMMM-yyyy}{GMT}{de-DE} %p %m%n"
  

That looks like the timezone argument were optional, but then this should also work, but does not:

•         "%d{dd-MMMM-yyyy}{de-DE} %p %m%n",
  

•         "%d{EEEE, dd. MMMM yyyy}{de-DE} %p %m%n",
  

In these two latter cases, the locale argument is silently ignored, i.e., when run on a system with an English locale, english month names are used.

I think it should either work (use the month names according to the locale specified) or be documented.

Configuration

Version: 2.26.0

Operating system: MacOS 26.5

JDK: 17

Reproduction

The original test is part of a rather large test suite for my Log4J compatible pattern parser. I can put some time into creating a JUnit test, but I'd like to know what you guys think of it as it's not clear if this is intended the way it works now (then documentation should be updated) or not (then I'd make it a real JUnit test). I had Codex create a minimal example just to give you an idea.

Log4jLocaleTest.java

[ramanathan1504]

@xzel23

Thanks for opening the issue and for providing the reproduction steps along with the initial fix. That helped a lot in understanding and validating the problem quickly.