All naked excepts which raise an exception should include previous exception stack

[Glenn Washburn <devlopment@…>]

I propose that there should be a strict policy for any new code being committed and all old code as it is found to be offending that any where there is a naked except, that is an except block that catches all exceptions, and an exception is raised within this block, that the previous exceptions exception call stack be preserved in the new raised exception.

For example, in contrib/admin/views/main.py on line 319 there is a naked except and the caught exception object is wrapped by another exception class and then re-raised. This loses the call stack of the originating exception, thus making it potentially very difficult to debug the original exception.

This issue should fix the above and start a policy discussion.

[Glenn Washburn <devlopment@…>]

I forgot to add. For those who don't know, there is a rarely used form of the "raise" statement as follows:

    raise ExceptionClass, exception_object, traceback

This form will use the provided traceback, as opposed to a traceback starting from the current frame. This is how I propose we preserve the originating exception's call stack. It would look something like the following:

    try:
        ....
    except Exception, e:
        raise ExceptionWrapperClass, ExceptionWrapperClass(e), sys.exc_info[2]

[Jannis Leidel]

Yeah, sounds like a good idea

[modi.konark@…]

Issued a PR against this ticket / patch : ​https://github.com/django/django/pull/930

[Carl Meyer <carl@…>]

In bc4111ba68e5eede1f68882a16d68441a845e30b:

Fixed #18003 -- Preserved tracebacks when re-raising errors.

Thanks jrothenbuhler for draft patch, Konark Modi for updates.