Package org.apache.groovy.contracts.ast

Class ThrowsIfASTTransformation

java.lang.Object
org.apache.groovy.contracts.ast.ThrowsIfASTTransformation
All Implemented Interfaces:
ASTTransformation
public class ThrowsIfASTTransformation extends Object implements ASTTransformation
Handles a method's ThrowsIf arm-set. Processed once per method (the transformation fires per annotation, so repeats are deduplicated via node metadata) because the semantics are per-set: guards are generated in declaration order, and the checked wrapper judges an escaping throw against every arm.

For each WOVEN-origin arm the guard-throw is generated at method entry, so that conceptually: 

 @ThrowsIf(value = { b == 0 }, exception = ArithmeticException)
 int divide(int a, int b) { a.intdiv(b) }
compiles as: 
 int divide(int a, int b) {
     if (b == 0) throw new ArithmeticException('@ThrowsIf: b == 0')
     a.intdiv(b)
 }
— the general form of the pattern groovy.transform.NullCheck provides for the null-check special case. Arms with woven = false generate no guard — the throw already exists, in the body (direct = true, the default) or in invoked code (direct = false); identical bytecode, the direct distinction is information for tools and is not read here.

When any arm is checked, the conditions are additionally snapshot on entry and the body is wrapped so that, conceptually: 

 boolean $c0 = <cond0>; ...                                 // entry snapshot, every arm
 if ($c0) throw new E0(...)                                  // woven arms, in declaration order
 Throwable $t = null
 try { <original body> }
 catch (Throwable caught) {
     $t = caught
     throw ThrowsIfSupport.onlyWhen(caught, [$c0, ...], [E0, ...], [texts], allExhaustive)
 } finally {
     if ($t == null) ThrowsIfSupport.mustThrow([unwoven $ci ...], [texts])   // normal return only
 }
A justified throw propagates untouched (defined behaviour); a broken implementation raises ThrowsIfViolation, never the declared exception. Non-woven arms with no checked flag anywhere generate nothing — runtime-retained metadata for tools.
Since:
6.0.0
See Also:

  • Constructor Details

    • ThrowsIfASTTransformation

      public ThrowsIfASTTransformation()

  • Method Details

    • visit

      public void visit(ASTNode[] nodes, SourceUnit source)
      Description copied from interface: ASTTransformation
      The method is invoked when an AST Transformation is active. For local transformations, it is invoked once each time the local annotation is encountered. For global transformations, it is invoked once for every source unit, which is typically a source file.
      Specified by:
      visit in interface ASTTransformation
      Parameters:
      nodes - The ASTnodes when the call was triggered. Element 0 is the AnnotationNode that triggered this annotation to be activated. Element 1 is the AnnotatedNode decorated, such as a MethodNode or ClassNode. For global transformations it is usually safe to ignore this parameter.
      source - The source unit being compiled. The source unit may contain several classes. For global transformations, information about the AST can be retrieved from this object.