[rules-users] Parser changes in trunk (for the next version)

[Edson Tirelli]

   All,

  Just a heads up for those using trunk. One of our main goals (from a
drools core perspective) for the next Drools version is to improve
consistency of the language and avoid some odd behaviors we had so
far, reducing users' surprises: e.g., add support to 100% of java
syntax for expressions, including things like generics; and avoid
different syntax when using java vs mvel, specially for constraints
that fall back to MVEL.

   As a result of this effort, there will be some changes to the DRL
language spec that might make your Drools 5.x DRL incompatible with
the next Drools version. Some are simple things, like the use of "||"
and "&&" between patterns that was deprecated (but still supported)
since Drools 4, but is now being completely removed and you must use
"or" and "and" respectively in between patterns. Some things are more
complicated.

   To help users that are migrating from Drools 5.1 to the next
version, we will keep the (now) old DRL parser (just renamed as
DRL5x.g) and will provide a migration tool that uses this parser to
translate an old DRL to the new syntax. This is a one time conversion
that you will have to apply to your source DRL files when migrating
from Drools 5.1 to the next version.

   I will commit the first cut of the new grammar later today into
trunk, so be advised that if you face errors after moving to a new
snapshot, it might have been caused by that. Please let me know if
that is the case and the migration tool fails to properly upgrade your
DRL. I will provide the link the migration tool documentation when I
commit the changes.

   Let me know if you have any questions.

   Edson

-- 
  Edson Tirelli
  JBoss Drools Core Development
  JBoss by Red Hat @ www.jboss.com