Log a thrown exception properly with backtrace

[aviks]

With this change, we get the following output. Haven't exported the function yet, happy to take naming suggestions.

julia> try 
         1 % 0
       catch e
          Logging.catch_err(e)
       end
29-Dec 11:48:17:ERROR:root:integer division error
 in rem at /Users/aviks/dev/julia/julia3/usr/lib/julia/sys.dylib

[aviks]

Hi @kmsquire any thoughts on this?

[kmsquire]

@aviks, sorry I never reviewed this. Are you still interested in pursuing it?

I think the idea seems pretty reasonable. However, I would implement it by specializing the individual logging functions (info, debug, err, etc.) to each have this behavior when passed an Exception. So your example would simply look like:

julia> try 
         1 % 0
       catch e
          Logging.err(e)
       end
29-Dec 11:48:17:ERROR:root:integer division error
 in rem at /Users/aviks/dev/julia/julia3/usr/lib/julia/sys.dylib

[aviks]

Yeah, that would have been a better API, this is ugly. Unfortunately, in Julia, exception objects don't seem to carry their backtraces with them. Backtraces can only be generated at a point in code, and so the Logging.catch_err function is useful only when called within a catch block. I wanted to signal that fact in the code, and hence a separate function. If we do Logging.err(e), then calling that method of err will again be effective only when called within a catch_block, but the function name or signature does not make that explicit. That seems like a recipe for misunderstanding, I thought.