HTTPException should retain cause information

[jcjf]

Long story short

I would like to use a pattern like:

try:
    do_something()
except SomeException as e:
    raise HTTPInternalServerError(reason='My message') from e

with cause information retained. Does it make sense to implement HTTPException.__bool__() to always True?

Expected behaviour

Two tracebacks separated by The above exception was the direct cause of the following exception:

Actual behaviour

The cause information is lost, because traceback.TracebackException evaluates the truthiness of the exception value to determine whether cause lines are produced. For HTTPException, truthiness is resolved via StreamResponse.__len__() which returns 0.

Steps to reproduce

Your environment

[asvetlov]

Yes, looks like __bool__ is the best we can do in the situation.
Would you make a Pull Request?

[lock]

This thread has been automatically locked since there has not been any recent activity after it was closed. Please open a [new issue] for related bugs.
If you feel like there's important points made in this discussion, please include those exceprts into that [new issue].
[new issue]: https://github.com/aio-libs/aiohttp/issues/new