The API client MAASClient doesn't encode list parameters when doing a GET

[Julian Edwards]

The code in maas_client.py assumes that all the parameters are strings and so fails with the stack trace below.

It would be more useful if it takes list params and encodes them appropriately. For example, if passed

client.get(url, op="thing", param=["foo", "bar", "baz"])

it should enode like this:

param=foo&param=bar&param=baz

In [9]: r=client.get(url, op="list", mac_address=["AA:BB:CC:DD:EE:FF", "AA:BB:CC:DD:EE:F0"])
---------------------------------------------------------------------------
AttributeError Traceback (most recent call last)
<ipython-input-9-63af12008a95> in <module>()
----> 1 r=client.get(url, op="list", mac_address=["AA:BB:CC:DD:EE:FF", "AA:BB:CC:DD:EE:F0"])

/home/ed/canonical/maas/sandbox/src/apiclient/maas_client.pyc in get(self, path, op, **kwargs)
    215 if op is not None:
    216 kwargs['op'] = op
--> 217 url, headers = self._formulate_get(path, kwargs)
    218 return self.dispatcher.dispatch_query(
    219 url, method="GET", headers=headers)

/home/ed/canonical/maas/sandbox/src/apiclient/maas_client.pyc in _formulate_get(self, path, params)
    176 url = self._make_url(path)
    177 if params is not None and len(params) > 0:
--> 178 url += "?" + urlencode(params.items())
    179 headers = {}
    180 self.auth.sign_request(url, headers)

/home/ed/canonical/maas/sandbox/src/apiclient/utils.pyc in urlencode(data)
     46 return b"&".join(
     47 b"%s=%s" % (enc(name), enc(value))
---> 48 for name, value in data)

/home/ed/canonical/maas/sandbox/src/apiclient/utils.pyc in <genexpr>((name, value))
     46 return b"&".join(
     47 b"%s=%s" % (enc(name), enc(value))
---> 48 for name, value in data)

/home/ed/canonical/maas/sandbox/src/apiclient/utils.pyc in <lambda>(string)
     43 """
     44 enc = lambda string: quote_plus(
---> 45 string.encode("utf-8") if isinstance(string, unicode) else string)
     46 return b"&".join(
     47 b"%s=%s" % (enc(name), enc(value))

/usr/lib/python2.7/urllib.pyc in quote_plus(s, safe)
   1293 s = quote(s, safe + ' ')
   1294 return s.replace(' ', '+')
-> 1295 return quote(s, safe)
   1296
   1297 def urlencode(query, doseq=0):

/usr/lib/python2.7/urllib.pyc in quote(s, safe)
   1284 safe = always_safe + safe
   1285 _safe_quoters[cachekey] = (quoter, safe)
-> 1286 if not s.rstrip(safe):
   1287 return s
   1288 return ''.join(map(quoter, s))

AttributeError: 'list' object has no attribute 'rstrip'

[Gavin Panella (allenap)]

Fwiw, ordering in a query string can be relevant, hence why
apiclient.utils.urlencode() accepts an iterable of (name, value) pairs,
and *not* a dict. Passing keyword arguments to get() - even with lists
of arguments - is lossy. However, that doesn't seem to be a concern in
MAAS right now.

So, two approaches I can think of:

1. Change get and co. to accept *args:

     def get(self, path, op=None, *args, **kwargs):
         query = urlencode(chain(args, kwargs.viewitems()))

   (I'm skipping over the details here; _formulate_get is where the
   encoding is done right now.)

2. Change get and co. to munge kwargs before sending off to urlencode:

     def flatten(kwargs):
         for name, value in kwargs.viewitems():
             if isinstance(value, (bytes, unicode)):
                 yield name, value
             else:
                 for v in value:
                     yield name, v

     def get(self, path, op=None, **kwargs):
         query = urlencode(flatten(kwargs))