Support switch expressions in Java 21; currently fails with "is not print idempotent" about rewrite HOT 3 OPEN

hi @gsmet Thanks for the tag! Indeed we haven't yet built in support for switch expressions into our Java 21 parser. Definitely should though; especially as we're eyeing a Java 21 upgrade internally too, which will make us feel this pain too.

from rewrite.

I think the issue is that OpenRewrite does not yet fully support Java's pattern matching for switch expressions and statements as previewed starting with Java 17 and then released with Java 21. This needs to be fixed in the parser (and printer).

from rewrite.

@timtebeek did this one fall through the cracks? I stumbled upon an old Quarkus issue complaining about it and this is a pattern that becomes more and more common.

In our case, the example was:

          return switch(rand) {
-            case String s -> s;
-            case Object o -> String.valueOf(o);
+            defaultcase String s -> s;
+            defaultcase Object o -> String.valueOf(o);
         };

from rewrite.