[GROOVY-4801] Thrown exception not accessable inside catch block when class has @Category transformation applied

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 1.7.10
• Fix Version/s: 1.8.1
• Component/s: ast builder
• Assignee: Paul King
• Reporter: Ewan Dawson
• Created: 28/Apr/11 06:08
• Updated: 07/Apr/15 19:13
• Resolved: 28/Apr/11 08:24

Description

When implementing a Category to handle exceptions, I find that the thrown exception is not available within the catch block when the class is annotated with the @Category AST transformation. Removing the @Category AST transformation gives the correct behaviour.

Example:

// Define exception handling category
@Category(Object)
class ExceptionHandler {
  def handled(Closure block) {
    try { block.call() }
    catch (Throwable t) { println t }
  }
}

// Define a class which mixes in this category
@Mixin(ExceptionHandler)
class Caller {
  def thrower() { handled { 1/0 } }
}

// Test the exception handling
new Caller().thrower()
// --> throws "ERROR groovy.lang.MissingPropertyException: No such property: t for class: Caller"

However, if the ExceptionHandler category is defined without using the @Category AST transformation:

class ExceptionHandler {
  static def handled(Object self, Closure block) {
    try { block.call() }
    catch (Throwable t) { println t }
  }
}

@Mixin(ExceptionHandler)
class Caller {
  def thrower() { handled { 1/0 } }
}

new Caller().thrower()
// --> prints "java.lang.ArithmeticException: Division by zero", as expected

This behaviour is observed both in the groovy shell, and in compiled code. Also, the erroneous behaviour is not due to the @Mixin AST transformation, as I observe the same behaviour when I replace the @Mixin AST transformation with the static initialization block {{

{Caller.mixin ExceptionHandler}

}} in the Caller class.