Explain Error Handling

Hi @kroitor and @xpl and all the developers of ccxt.

I’m have a few questions about error handling in ccxt. So there are ~two~ three main methods that are in the source of most exchanges for handling errors:

• handleErrors
• throwErrorOnException
• request

I gather that handleErrors called in fetch and throwErrorOnException is called pretty much anywhere. However I also see some errors get thrown in request and I’m not really sure if they should be raised there.

Could someone explain how these two methods are supposed to work together. Moreover, @kroitor was talking about only parsing JSON once before but I’m not sure where this should take place. Is

All the best, frosty

[mkutny]

I think this might be a misconception, we can’t really throw http codes away easily, because there are exchanges that will report http error codes instead of internal codes, and we really need to differentiate between them sometimes…

As I’ve got the question was about dropping http status text, not about http status code. The code is needed, indeed. The text (i.e. reason) is not used.

What I would actually do (when the flow is unified) is switch handleErrors signature to options pattern, it’d make us flexible in args. Still, as far as I remember there were some tensions on Python side.

[mkutny]

Surely it would make sense to move the logic to handleErrors for consistency?

It’s called by handleErrors anyway. Feel free to move it, although it either won’t be as concise or will parse json twice.

why is this additional logic required?

Because sometimes we expect json (and we should throw if json is not received) and sometimes we expect plaintext (and should proceed if json is not received). Alternatively, it could be something like:

try:
    json.loads(request.body)
except ValueError:
    if jsonRequired:
        raise
    else:
        pass