Add support to test caught exceptions

[cpollet]

I would like to be able to assert that some method calls are wrapped in a try/catch block catching certain type of exceptions.

Typical use case would be to make sure that runtime WebApplicationExceptions are caught when calling a remote resource using JAX-RS.

I'd be happy to try to contribute with a PR, if it could eventually be merged.

[hankem]

ArchUnit currently does not recognize

the bytecode signature of try/catch blocks,

For a simple example

    try {
        RemoteService.method();
    } catch (WebApplicationException e) {
        e.printStackTrace();
    }

the byte code looks like this (see also JVM Spec §3.12):

   0: invokestatic  #2      // Method RemoteService.method:()V
   3: goto          11
   6: astore_1
   7: aload_1
   8: invokevirtual #4      // Method javax/ws/rs/WebApplicationException.printStackTrace:()V
  11: return
Exception table:
   from    to  target type
       0     3     6   Class javax/ws/rs/WebApplicationException

Try-with-resources statements are even more complex.

For example,

    try (RemoteService remoteService = new RemoteService()) {
        remoteService.method();
    } catch (WebApplicationException e) {
        e.printStackTrace();
    }

compiles to the following byte code:

   0: new           #2      // class RemoteService
   3: dup
   4: invokespecial #3      // Method RemoteService."<init>":()V
   7: astore_1
   8: aload_1
   9: invokevirtual #4      // Method RemoteService.method:()V
  12: aload_1
  13: invokevirtual #5      // Method RemoteService.close:()V
  16: goto          35
  19: astore_2
  20: aload_1
  21: invokevirtual #5      // Method RemoteService.close:()V
  24: goto          33
  27: astore_3
  28: aload_2
  29: aload_3
  30: invokevirtual #7      // Method java/lang/Throwable.addSuppressed:(Ljava/lang/Throwable;)V
  33: aload_2
  34: athrow
  35: goto          43
  38: astore_1
  39: aload_1
  40: invokevirtual #9      // Method javax/ws/rs/WebApplicationException.printStackTrace:()V
  43: return
Exception table:
   from    to  target type
       8    12    19   Class java/lang/Throwable
      20    24    27   Class java/lang/Throwable
       0    35    38   Class javax/ws/rs/WebApplicationException

but ASM offers MethodVisitor.html.visitTryCatchBlock, which could be implemented in ArchUnit's MethodProcessor.

How would you want to make the information available in ArchUnit's domain objects?
Should JavaCall have something like Set<JavaClass> getCaughtExceptions()?

[codecholeric]

This might be a nice addition, but I would propose a type CaughtException or sth. like that (similar to InstanceOfCheck) that can offer you type and source code location (and possibly more info in the future).

[crizzis]

PR attached.

(Sorry if sth is not quite done the 'ArchUnit way', but this is my first PR here)