Remove Consumer falsiness.

[wting]

I ran into an issue where 0 (a legitimate partition id) is interpreted as the same as None and thus giving me the results for all partitions (e.g. in Consumer.pending()).

[dpkp]

partitions is a list... [] is false, [0] is true. can you provide a test case? I dont think this PR does what you think it does.

[wting]

If I call Consumer.pending(0) I'm (incorrectly) expecting the list of pending messages for partition id 0. However this will fail the falsy check if not partitions: and returns pending messages for all partitions.

It is preferable to fail fast and complain that the function expects a list and not an integer.

[15] λ consumer.fetch_offsets.items()
[15] » [(0, 0)]

[16] λ consumer.pending(0)
[16] » 101

[17] λ consumer.pending([0])
[17] » 101

[18] λ consumer.pending(1)
---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-18-a9f596a67196> in <module>()
----> 1 consumer.pending(1)

/nail/home/wting/corner/pfpg/virtualenv_run/lib/python2.6/site-packages/kafka/consumer/base.pyc in pending(self, partitions)
    161         reqs = []
    162 
--> 163         for partition in partitions:
    164             reqs.append(OffsetRequest(self.topic, partition, -1, 1))
    165 

TypeError: 'int' object is not iterable

[19] λ consumer.pending([1])
---------------------------------------------------------------------------
UnknownTopicOrPartitionError              Traceback (most recent call last)
<ipython-input-19-e533b14c0e3a> in <module>()
----> 1 consumer.pending([1])

/nail/home/wting/corner/pfpg/virtualenv_run/lib/python2.6/site-packages/kafka/consumer/base.pyc in pending(self, partitions)
    164             reqs.append(OffsetRequest(self.topic, partition, -1, 1))
    165 
--> 166         resps = self.client.send_offset_request(reqs)
    167         for resp in resps:
    168             partition = resp.partition

/nail/home/wting/corner/pfpg/virtualenv_run/lib/python2.6/site-packages/kafka/client.pyc in send_offset_request(self, payloads, fail_on_error, callback)
    455             payloads,
    456             KafkaProtocol.encode_offset_request,
--> 457             KafkaProtocol.decode_offset_response)
    458 
    459         out = []

/nail/home/wting/corner/pfpg/virtualenv_run/lib/python2.6/site-packages/kafka/client.pyc in _send_broker_aware_request(self, payloads, encoder_fn, decoder_fn)
    156         for payload in payloads:
    157             leader = self._get_leader_for_partition(payload.topic,
--> 158                                                     payload.partition)
    159 
    160             payloads_by_broker[leader].append(payload)

/nail/home/wting/corner/pfpg/virtualenv_run/lib/python2.6/site-packages/kafka/client.pyc in _get_leader_for_partition(self, topic, partition)
     87         # If the partition doesn't actually exist, raise
     88         if partition not in self.topic_partitions[topic]:
---> 89             raise UnknownTopicOrPartitionError(key)
     90 
     91         # If there's no leader for the partition, raise

UnknownTopicOrPartitionError: TopicAndPartition(topic='topic', partition=1)

[dpkp]

Ok -- I see your point and think this is worth merging, though I am going to add a separate issue to support the interface you were expecting: Consumer.pending(0)

[dpkp]

merged