fix: error in IPython while handling HTTP4xxClientError

[seeM]

For example:

In [1]: from ghapi.core import *

In [2]: GhApi().repos.get('org', 'not-a-real-repo-123123123')
Unexpected exception formatting exception. Falling back to standard exception
Traceback (most recent call last):
  File "/Users/seem/.pyenv/versions/3.9.13/lib/python3.9/site-packages/IPython/core/interactiveshell.py", line 3398, in run_code
    exec(code_obj, self.user_global_ns, self.user_ns)
  File "<ipython-input-2-b91955617868>", line 1, in <cell line: 1>
    GhApi().repos.get('org', 'not-a-real-repo-123123123')
  File "/Users/seem/code/ghapi/ghapi/core.py", line 61, in __call__
    return self.client(self.path, self.verb, headers=headers, route=route_p, query=query_p, data=data_p)
  File "/Users/seem/code/ghapi/ghapi/core.py", line 118, in __call__
    res,self.recv_hdrs = urlsend(path, verb, headers=headers or None, debug=debug, return_headers=True,
  File "/Users/seem/code/fastcore/fastcore/net.py", line 217, in urlsend
    return urlread(req, return_json=return_json, return_headers=return_headers)
  File "/Users/seem/code/fastcore/fastcore/net.py", line 118, in urlread
    if 400 <= e.code < 500: raise ExceptionsHTTP[e.code](e.url, e.hdrs, e.fp, msg=e.msg) from None
fastcore.basics.HTTP404NotFoundError: HTTP Error 404: Not Found
====Error Body====
{
  "message": "Not Found",
  "documentation_url": "https://docs.github.com/rest/reference/repos#get-a-repository"
}


During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "/Users/seem/.pyenv/versions/3.9.13/lib/python3.9/site-packages/IPython/core/interactiveshell.py", line 1990, in showtraceback
    if hasattr(value, "_render_traceback_"):
  File "/Users/seem/.pyenv/versions/3.9.13/lib/python3.9/tempfile.py", line 472, in __getattr__
    file = self.__dict__['file']
KeyError: 'file'

cc @hamelsmu @jph00

[review-notebook-app]

Check out this pull request on 

See visual diffs & provide feedback on Jupyter Notebooks.

---

Powered by ReviewNB

[seeM]

The crux is to override the __init__ set by get_class to call super().__init__.

The _mk_error function was needed so that _init is included as-is in the closure. Without _mk_error, each iteration of the for loop would overwrite the previously defined _init.

[jph00]

This is getting pretty obscure! Is there any simpler way to do this, even if a bit more verbose?

[seeM]

Do you like having separate classes for each error code?

[seeM]

I think I'd prefer to use the urllib.HTTPError class

[jph00]

The thing I do want is to be able to catch exceptions based on what kind of error occurred. Is there a way to do that without separate classes?

[jph00]

Would using type(name, bases, attributes) directly be an easier way to create these?

[seeM]

I think like so:

try: urlopen(...)
except HTTPError as e:
    if e.code != 401: raise
    # ...

[seeM]

Would using type(name, bases, attributes) directly be an easier way to create these?

I thought about it. type(nm, (HTTP4xxClientError,), {'code': code, 'msg': msg}) works and is concise, but would be a tiny breaking change in the signature, from current:

def __init__(self, url, hdrs, fp, msg=default_msg, code=default_code):

to the parent class':

def __init__(self, url, code, msg, hdrs, fp)

That might be okay though

[jph00]

Could you add __init__ to those attrs to get the init we want?

[seeM]

@jph00 I think this is much better with your suggestion to use type.

Another thing that simplifies it is to directly call HTTP4xxClientError.__init__ instead of super(...), because:

1. Using super dynamically like this requires explicitly passing the cls. And in order to pass a different cls each time, we need to define _init in a closure to avoid overwriting it with each cls.
2. Since _init needs a reference to cls, we have to first define it with type(...) and then patch cls.__init__.

This of course has the downside that HTTP4xxClientError is hardcoded instead of having super's behaviour.

[seeM]

Out of interest, this seems to work too, but I think it's more obscure:

for code,msg in _httperrors:
    class _(HTTP4xxClientError):
        def __init__(self, url, hdrs, fp, msg=msg, code=code): super().__init__(url, code, msg, hdrs, fp)
    _.__name__ = f'HTTP{code}{msg.replace(" ","")}Error'
    _.__qualname__ = _.__qualname__.split('.')[0] + _.__name__
    globals()[nm] = ExceptionsHTTP[code] = _

[jph00]

I guess in that case I'd have a function like:

get _httperrcls(url, code, msg, hdrs, fp):
    class _c(HTTP4xxClientError):
            def __init__(self, url, hdrs, fp, msg=msg, code=code): super().__init__(url, code, msg, hdrs, fp)
     _c.__name__ = f'HTTP{code}{msg.replace(" ","")}Error'
     _c.__qualname__ = _.__qualname__.split('.')[0] + _c.__name__
    return _c

[jph00]

Yay!