[I] org.mvel2.CompileException on Drools Template file with parameters in constraints [incubator-kie-drools]

["Cocoa-Puffs (via GitHub)" <gi...@apache.org>]

Cocoa-Puffs opened a new issue, #6154:
URL: https://github.com/apache/incubator-kie-drools/issues/6154

   Java Version: 21
   Spring Boot Version: 3.3.4
   KIE Version: 9.44.0.Final
   
   Short summary:
   In Drools Template files if there are parameters on a given line that end with a variable name a trailing space must be the last character of the line or during compiling an exception is thrown stating that unclosed @if{} blocks exist in the template file.
   
   Detailed explanation:
   Take for example the following drt snippet:
   ```
   when
       $c: Customer($balances : balances != null)
       $b_thb: Balance(currency == "@{balanceType}") from $balances
   then
   ``` 
   
   Using either DataProviderCompiler or ObjectDataCompiler to compile the above I get the following error:
   
   Caused by: org.mvel2.CompileException: [Error: unclosed @if{} block. expected @end{}]
   [Near : {... nceType}");@end{} ....}]
   
   The exception references the end of the action block. However when I replace the parameter with a concrete example:
   
   ```
   when
       $c: Customer($balances : balances != null)
       $b_thb: Balance(currency == "MAGIC_COIN") from $balances
   then
   ``` 
   
   The exception does not come. After a bit of digging around with the debugger I have found that what happens is during compile time KIE wraps every line in if statements that use a parameter, for example the above snippet turns into:
   
   ```
   when
       $c: Customer($balances : balances != null)
   @if{balanceType != null}    $b_thb: Balance(currency == "@{balanceType}") from $balances@end{}
   then
   ``` 
   
   It then fails to read the @end{} statement as the closure of the if at the beginning of the line resulting in an exception. If I then modify the drt file to have a space at the end of this line the compilation is successful. Checking out the ExpressionNode using the debugger we can see the following:
   
   ```
   when
       $c: Customer($balances : balances != null)
   @if{balanceType != null}    $b_thb: Balance(currency == "@{balanceType}") from $balances @end{}
   then
   ``` 


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