Support chained exceptions

[cdemyanovich]

In Ruby 2.1.0, Exception#cause was added. While @dcramer informed me in #sentry on irc.freenode.net that the Sentry server already supports chained exceptions, the Ruby client does not. I propose that we add support for chained exceptions to the Ruby client. We could just detect whether an exception responds to #cause and, if so, add the cause's message and backtrace to the exception report.

I'm just opening this for discussion now. I may propose this work as a "10% time" project at my current client or try to work on it myself as early as this weekend.

[seanlinsley]

I'd love to see this as well. I'm not familiar with raven-ruby's codebase though, so I wouldn't be much help.

[cdemyanovich]

I've been poking around the source of the server and the different client libraries via the GitHub web UI. I haven't found a place where the message format for chained exceptions is documented/implemented. Could you point me in the right direction, @dcramer?

[dcramer]

Yep it's all here:

http://sentry.readthedocs.org/en/latest/developer/interfaces/index.html#sentry.interfaces.exception.Exception

[nateberkopec]

I've never needed to use a chained exception - but I think in Sentry this would mean adding an exception (the exception in Exception#cause) to the exception list in the event?

Do we need to support an arbitrary number of levels of Exception#cause, calling Exception#cause on each member of the chain and adding those to the exception list?

[WattsInABox]

Yeah, I think raven-ruby should support a chain of exceptions. One of the most annoying things in PDI (written in Java) was when a database error occurred and it would say "call getNextException to see the cause" and, of course, no one writing that program thought to call that function.

[cdemyanovich]

I'm won't be submitting a PR. I've long since moved on to another project in Clojure. In an earlier comment, @dcramer linked to documentation that should help: http://sentry.readthedocs.org/en/latest/developer/interfaces/index.html#sentry.interfaces.exception.Exception.